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View the video below for several personal accounts of this disease, information from encephalitis specialists, and a call for increased awareness.

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Raising awareness for Autoimmune Encephalitis, because all too often this disease goes misdiagnosed or is not diagnosed at all.

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First line therapies:

tumor (if present) removal

steroid treatment

IVIG (intravenous immunoglobulin) therapy to prevent antibody binding

plasmapheresis to filter out antibodies from the blood

If the above therapies do not improve symptoms some "second-line" treatments are used:

Rituximab

CellCept

Cytoxan

These drugs heavily suppress the immune system response.

Sources:

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Autoimmune encephalitis is a difficult clinical diagnosis due to the similarities in the clinical, imaging and laboratory findings of many forms of autoimmune and infectious encephalitis. Patients generally have impaired memory and cognition over a period of days or weeks. There may be clues to specific causes on history of physical examination, but often these specific signs are absent. A broad approach to testing for infectious diseases and various neuronal autoantibodies can lead to the correct diagnosis. If a clear autoimmune cause for the symptoms is established, treatment usually involves escalating immune therapies. The process of caring for these patients requires patience and repeated evaluations to determine the proper degree of immune therapy needed at any given time.

Autoimmune encephalitis involves several types of diseases with different pathophysiology. Understanding the pathophysiology of these diseases is helpful in using diagnostic testing and choosing appropriate therapies. The first group includes the classic paraneoplastic disorders associated with antibodies to intracellular antigens, such as anti-Hu. These disorders are strongly cancer associated and involve T-cell responses targeting neurons. The prognosis tends to be poor due to irreversible neuronal killing by these mechanisms, the severity of associated cancers, and the difficulty in controlling these sorts of immune responsess. The antibodies in these disorders are useful tumor markers, and in the appropriate context and titer also useful markers of the paraneoplastic neurological disorders. The antibodies themselves are not directly pathogenic. The second group involves autoantibodies to extracellular epitopes of ion channels, receptors and other associated proteins, such as the NMDA receptor. The cancer associations are variable, and the prognosis tends to be much better. The antibodies in these disorders are thought to be directly pathogenic, causing reversible effects on synaptic function in neurons with relatively little neuronal death. There are also important tumor associations in this group of diseases. For instance, patients with anti-NMDAR encephalitis commonly can recover from a totally unresponsive state to eventually resume a good quality of life. Occupying an intermediate position are diseases with autoantibodies to intracellular synaptic proteins such as GAD65. It is unclear whether this group involves T-cell responses and/or functional effects of antibodies. A final group includes other forms of autoimmune encephalitis in which precise antigens are less clearly established, such as lupus cerebritis or ADEM. Some diseases in this group have systemic manifestations outside the nervous system. This review will focus on the disorders with well-defined brain antibodies.

Autoimmune encephalitis can manifest with several distinct syndromes, complicating its recognition. The classical presentation of encephalitis consists of a subacute (days to a few weeks) progressive decrease in the level of consciousness, often with fluctuations, and altered cognition. Memory, especially retention of new information, may be impaired early in the clinical course. Patients may progress to coma. While many cases of autoimmune encephalitis are indistinguishable from each other or viral encephalitis, there may be clues to specific autoimmune etiologies ().

Abnormal movements may be the presenting symptom in several types of autoimmune encephalitis. These include anti-NMDAR encephalitis, where movement symptoms may occur early in the disease course, especially in children, who generally have more motor symptoms and fewer psychiatric symptoms than adults. These may resemble dystonia or chorea, with writhing and fixed abnormal postures of the limbs. In adults with anti-NMDAR encephalitis, writhing movements of the face and limbs may be most prominent in the comatose phases of the illness. GAD65 and GlyR autoimmunity may present with stiff person syndrome (SPS) or progressive encephalomyelitis with rigidity and myoclonus (PERM). A striking feature of PERM with GlyR antibodies is a pathologically exaggerated startle response, resembling hereditary hyperekplexia, a genetic disease caused by GlyR mutations. Although there is some degree of overlap, GAD65 is more associated with classical SPS while GlyR antibodies may be seen more with symptoms of hyperekplexia and myoclonus, which are prominent in PERM. Stiffness or exaggerated startle combined with other symptoms of encephalitis should raise concern for GlyR antibodies. Basal ganglia encephalitis has also been reported with D2R antibodies, although this may be very rare. Sydenham chorea is a well-recognized autoimmune movement disorder thought to be triggered by streptococcal infections and should be considered in children with this presentation.

Seizures are common in autoimmune encephalitis and may be a presenting symptom. In anti-NMDAR encephalitis seizures may occur at any stage of the illness. Autoantibodies to two important inhibitory receptors in the brain, GABA-B and GABA-A receptors (at high titer) convey a high risk of severe seizures and intractable status epilepticus. GAD65 antibodies may present with epilepsy, perhaps also with memory impairment, but with few other symptoms to suggest an autoimmune etiology. GAD65 autoimmunity may therefore resemble other forms of treatmentresistant epilepsy. Fasciobrachial dystonic seizures (FBDS) are brief seizures consisting of rapid jerks of the face and/or ipsilateral arm and shoulder. Seizures may be partial or associated with temporary disruptions in consciousness and may be multifocal and variable on EEG. FBDS are characteristic of LGI1 autoimmunity and may precede other symptoms of the disease by weeks or months. Patients may have hundreds of these seizures per day. These seizures may have only limited response to seizure medications but respond well to immune therapies.

Cerebellitis is a distinct syndrome of ataxia of gait, limb movements, eye movements, voice, and/or swallowing. The precise mixture of symptoms varies from patient to patient. Vertigo and nystagmus are common. Cerebellitis may occur with infectious causes, but the presentation of a subacute cerebellar syndrome portends a good probability a specific autoimmune etiology and also a significant risk of tumors. Paraneoplastic cerebellar degeneration is associated with conventional onconeuronal autoantibodies such as Yo, but also with cell surface autoantibodies targeting mGluR1, DNER, and other antibodies. GAD65 antibodies are perhaps the most common finding in this phenotype in my experience. Autoimmune cerebellitis may result in the irreversible loss of Purkinje neurons, and the prognosis is recovery may be poorer than with other types of autoimmune encephalitis.

Certain types of autoimmune encephalitis may precede or follow neuromuscular manifestations, particularly acquired neuromyotonia (Isaacs syndrome). Isaacs syndrome presents with muscle spasms, cramps and fasciculations due to peripheral nerve hyper-excitability. Morvan syndrome (Morvan's fibrilllary chorea) consists of peripheral nerve hyper-excitability with encephalitis and severe insomnia. Some cases of Isaacs syndrome are associated with autoantibodies to Caspr2 or other, often undefined, members of the voltage-gated potassium channel (VGKC) complex. Caspr2 antibodies are even more likely in patients with Morvan syndrome, especially patients with thymoma, who may have multiple autoimmune disorders during their disease course. Encephalitis with these neuromuscular manifestations (myasthenia gravis, neuromyotonia) therefore suggests a specific autoimmune etiology.

As discussed below, most of the autoimmune causes of encephalitis are paraneoplastic, each conveying a risk profile for various tumors. Detecting particular tumors may therefore also suggest particular autoimmune causes. For instance, the likelihood of anti-NMDAR encephalitis is increased in a young woman with ovarian teratoma, and the likelihood of anti-DNER is higher in patients with cerebellar degeneration and Hodgkin lymphoma.

In addition to the antibody-mediated and paraneoplastic forms of encephalitis, there are other autoimmune diseases that may present with encephalitis. In the case of ADEM, encephalitis is a common presentation. The characteristic brain lesions, and sometimes involvement of the optic nerves or spinal cord, are an important clue to diagnosis.

Multiple sclerosis (MS) is generally easier to distinguish from autoimmune encephalitis due to more focal symptoms and characteristic brain imaging findings.

Vasculitis affecting the CNS may rarely present with symptoms resembling encephalitis. When this is suspected, imaging of the cerebral vessels, search for other evidence of vasculitis (such as serologies for lupus and other rheumatologic diseases) may be useful.

Bickerstaff encephalitis and Miller Fisher syndrome enter into the differential diagnosis of autoimmune encephalitis due to the presence of altered mental status and/or cranial neuropathies. These diseases may at first resemble the brain-stem syndrome associated with anti-Ri, but the loss of reflexes is an important clue suggesting Miller Fisher syndrome. Detection of the GQ1b antibody may be helpful in securing these diagnoses.

A detailed travel and exposure history is essential. For instance, West Nile encephalitis has been reported only once in Korea, in a patient who had recently traveled to Guinea. Travel to areas endemic for malaria or Lyme disease may be similarly relevant. Exposure to persons with tuberculosis or other infectious agents may be a clue to diagnosis.

Human herpesvirus 6 (HHV-6), and less often HHV-7, may cause encephalitis and their reactivation may be an important cause of encephalitis in transplant patients. HHV-6 and HHV-7 are diagnosed by PCR, although this may not be positive initially. There are no approved treatments, but ganciclovir, foscarnet, and cidofovir have been used. HHV-6 may be more likely in cases whether the donor and/or recipient of a stem cell transplant carry a particular HLA type (HLA-B* 40:06).

Due to the diversity of potential infections, using a separate test for each pathogen may not be practical. To address this issue, advanced genetic techniques (e.g., metagenomic deep sequencing of cerebrospinal fluid) have been proposed to screen for thousands of pathogens rapidly and efficiently. Early successes with this approach have included diagnosing cases of encephalitis due to leptospirosis, neurotropic astrovirus infection, Balamuthia mandrillaris, and squirrel bornavirus. This approach should assume a wider role in diagnosing unusual CNS infections in the coming years.

Cerebellitis may occur as an infectious or post-infectious phenomenon. Leading viral causes include VZV, JC virus, influenza, EBV, and enterovirus. Numerous other bacterial, fungal, malignant, and other causes have also been reported.

Intoxications such a neuroleptic malignant syndrome and serotonin syndrome may often present with similarities to autoimmune encephalitis. Conversely, patients with anti-NMDAR encephalitis may develop psychosis as an initial symptom and be treated with neuroleptics, then later show catatonia, rigidity, autonomic instability and altered level of consciousness; this pattern of findings may be mistaken for neuroleptic malignant syndrome. Autoimmune encephalitis therefore should enter into the differential diagnosis of any case of suspected neuroleptic malignant syndrome (Patients with anti-NMDAR encephalitis may be particularly sensitive to strong dopamine antagonists, and our group attempts to avoid using these medications).

Lymphoma or carcinomatous meningitis may present similarly to autoimmune encephalitis. Particularly, symptoms may have a subacute onset and involve multiple cranial neuropathies. Both may occur in patients with or without known tumors. Repeating CSF cytology, awareness of known tumors, and screening for malignancy may all help lead to recognition of these causes.

Antibody testing

Autoantibody testing is extremely important for the proper diagnosis of autoimmune encephalitis. However, the tests have complexities that require consideration, and taking certain test results as conclusive evidence of autoimmune encephalitis can be a mistake.

Commercial tests for autoantibodies to NMDAR, LGI1, Caspr2, AMPAR (GluR1, GluR2 subunits), and GABA-B-R are widely available. Newer cell surface antigens like GABAA-R and DPPX are more difficult to test clinically. The synaptic intracellular antigens GAD65 and Amphiphysin, as well as the conventional intracellular "onconeuronal" antibodies are widely available. In the correct clinical context, these antibodies can be diagnostic. But there are complexities to interpreting some of these tests.

The availability of titers for NMDAR antibodies has led some practitioners to attempt to use these titers to guide treatment. However, titers have limited clinical utility for several reasons: 1) absolute titers provide little information on disease severity, 2) titers in serum do not correlate reliably with disease status, and 3) CSF titers correlate only roughly to disease status within a given patient using side-by-side comparisons of multiple samples. Therefore, it is better to focus on the clinical status of the patient and not changes in antibody titer during the early phases of the illness. NMDAR CSF titers may be compared to earlier samples sideby-side in assessing whether clinical worsening represents a true relapse, but this is only rarely helpful.

Caspr2 and LGI1 each associate with VGKCs. The VGKC antibody test is based on immunoprecipitation of a complex of protein containing VGKCs, LGI1, Caspr2 and other proteins. The VGKC RIA was created 15 years before the recognition of LGI1 or Caspr2 antibodies, and patients with these antibodies were thought, incorrectly, to actually have antibodies to potassium channel subunits themselves. The VGKC test may still detect patients with LGI1 or Caspr2 immunity, but low titer serum positive results have uncertain clinical significance. For instance, Paterson et al. reported that only 4 of 32 patients with low titer VGKC results (100-400 pM) actually had an autoimmune disorder. Thus a low titer serum VGKC result without corresponding evidence of LGI1 or Caspr2 antibodies, ideally in the CSF, should not be taken as definitive evidence of autoimmune encephalitis.

GAD65 antibodies have diverse clinical correlates, including SPS, cerebellar degeneration, epilepsy, and type 1 diabetes. In the context of encephalitis, especially with epilepsy, a CSF GAD65 response is evidence of an autoimmune etiology. However, GAD65 may co-exist with other autoantibodies, such as GABA-B-R, so may or may not represent the most relevant pathophysiological mechanism in some patients with multiple antibodies. In addition, low titer GAD65 serum responses may not be specific for a neurological disorder, and GAD65 serum antibodies provide little additional information in a patient with known type 1 diabetes. Conversely, I have observed patients who develop type 1 diabetes after the onset of their neurological syndrome in the context of GAD65 antibodies. Testing CSF of these patients for GAD65 and a panel of other autoantibodies may be informative in these cases.

Hashimoto's encephalopathy is generally defined as encephalopathy associated with thyroid autoantibodies that responds to steroids or other immune therapies. It has not been shown that thyroid antibodies can directly affect the brain, and the abnormalities in thyroid hormone levels are generally too mild to explain the brain disease. Some of these cases are due to other autoantibodies, such as to the NMDAR or GABA-B-R, but the true cause of most cases is unknown. Thyroid antibodies are therefore sometime tested in patients with autoimmune encephalitis. Finding thyroid antibodies should prompt a careful search for responsive other autoantibodies to brain that would provide a more convincing explanation of the symptoms. But if these antibodies are not found immune therapy should be considered.

Imaging

Brain MRI in patients with NMDAR, AMPAR, LGI1, Caspr2, and GABA-B antibodies may be normal or show increased T2 signal, especially in the medial temporal lobes. This pattern is similar to the findings seen in HSV encephalitis, where 95% of patients have abnormalities on MRI, or other viral causes of encephalitis. Tuberculosis, Syphilis, or other infections may present similarly. Autoantibodies to DPPX or GABA-A may have less characteristic findings. Brain MRI therefore does not distinguish between infectious and autoimmune causes, and a normal brain MRI does not exclude these causes.

Advanced brain imaging with PET or SPECT has shown diverse areas of regional hyper- or hypo-metabolism in patients with NMDAR, LGI1, Caspr2 or other autoantibodies. These studies have not reached the point where any particular form of encephalitis can be distinguished from another, so I do not generally rely on these studies to rule in or rule out autoimmune causes in my practice.

EEG

EEG is useful in patients with autoimmune or infectious encephalitis for excluding subclinical seizures, for prognosis, and sometimes for suggesting particular diagnoses. In patients with HSV encephalitis, EEG may predict prognosis in addition to helping exclude non-convulsive seizures; normal EEG correlates with good outcomes independent of other prognostic factors.

Status epilepticus may occur in several forms of autoimmune encephalitis. The highest risk appears to be in patients with autoantibodies to the major brain inhibitory receptors GABA-A and GABA-B. High-titer antibodies to either of these antigens conveys a risk of status, which may be refractory to the unusual treatments. Since these antibodies are both much rarer than other autoantibodies to the NMDA receptor, the status epilepticus in the setting of autoimmune encephalitis probably occurs more frequently with NMDAR antibodies overall.

LGI1 antibodies are associated with FBDS, which may present weeks or months prior to other symptoms. The clinical characteristics of these seizures are distinctive, involving rapid jerking of one side of the face and/or upper extremity. Each seizure tends to be unilateral but they may occur on both sides. Some events are simple partial and very rapid, but complex partial seizures may occur as they become more frequent. EEG may show multifocal onset seizures and other abnormalities.

In my experience, seizures in autoimmune encephalitis are associated with active disease (e.g., are unlikely to persist after remission of other symptoms of autoimmune encephalitis). These seizures may be very difficult to control with antiseizure medications until the autoimmune disease is treated.

Biopsy

Brain biopsy generally is not used in the diagnosis of encephalitis for several reasons. Infections may be detected by PCR, culture or other less invasive methods. The well-defined autoantibody causes typically have antibody tests that are much less invasive and much more definitive. In addition, the results of biopsy are generally not definitive for a particular autoimmune etiology. Overall, the clinical impact of biopsy done for suspected encephalitis is low, with only about 8% of cases having clear benefit.

Cancer screening

Paraneoplastic disorders are, in general, autoimmune disorders that are triggered by tumors. In many cases the target antigen is expressed by tumor tissue, such as HuD proteins in small cell lung cancer and NMDARs in ovarian teratoma. In these patients it is likely that presentation of the antigen in the context of the tumor triggers the autoimmune response. However, other patients without tumors may have an identical clinical syndrome and immunological response (antibody specificity, neuropathology, etc.).

It is important to detect tumors promptly for several reasons. 1) Treating the relevant tumor is thought to be helpful for treating the autoimmune disorder. 2) Tumor therapy and immune therapy may need to be given simultaneously and in a coordinated fashion. 3) Treatment with steroids, rituximab, or cyclophosphamide could complicate tumor diagnosis in the case of tumors like lymphoma.

In the case of "onconeuronal" antibodies to intracellular antigens such as Hu, the antibodies may occur more commonly in cancer patients than in patients with the autoimmune disease. For instance low titer serum Hu responses are common in small cell lung cancer patients without the anti-Hu neurological syndromes. For this reason, finding such an antibody should prompt a careful evaluation for tumor even if there is not a corresponding autoimmune disease. For instance, an elderly diabetic smoker may be tested (inappropriately) for anti-Hu to evaluate a mild slowly progressive small fiber neuropathy. In this case, a low titer serum Hu antibody would be far less likely to explain the neuropathy than the diabetes, but should nonetheless prompt screening for lung cancer. Similarly, a patient with known lung cancer may develop neuropathy after chemotherapy; finding Hu antibodies in such a patient should not be taken as definitive evidence of a paraneoplastic disorder.

Cell surface/synaptic antibodies are generally found in the spinal fluid only in patients with the relevant neurological disorder and are not found incidentally. Each of these antibodies has a cancer risk profile that should inform the search for tumors.

The testing strategy depends on the specific autoantibody and/or clinical syndrome. Where there is risk for lung cancer or other solid tumors, CT scans and PET/CT may be appropriate. In syndromes associated with ovarian teratoma, evaluation with ultrasound or pelvic MRI. In young men where Ma2 is diagnosed or suspected testicular ultrasound is important. Breast imaging with mammogram or MRI, pap smear, and pelvic imaging may be most helpful in women with anti-Yo. Screening should be broad in patients with high-risk syndromes such as cerebellar degeneration even when a particular antibody is not identified. Tumors may be very small when the neurological symptoms begin, so screening is typically done on initial presentation and repeated at increasing intervals. For instance, a young woman with anti-NMDAR encephalitis may have pelvic MRI at diagnosis, and repeated studies at 6 months, 1 year, and 2 years. A patient with DNER antibodies (conveying a 90% risk of Hodgkin lymphoma) might have PET-CT at diagnosis then close follow-up with an oncologist and repeat studies starting 3-4 months later.

Autoantibodies to cell surface antigens

Anti-NMDAR (N-methyl-D-aspartate receptor) encephalitis has a characteristic clinical syndrome in most patients. Symptoms of psychosis and memory impairment are commonly the initial findings with abnormal movements, seizures, and depressed level of consciousness emerging later. Patients may experience the psychotic symptoms again as they wake form coma, a phenomenon analogous to the psychotic symptoms seen after recovery from phencyclidine anesthesia (Phencyclidine, also known as PCP or "angel dust", is an NMDAR antagonist developed as an anesthetic but is not used due to the high risk of psychosis). Ovarian teratoma affects many female patients of reproductive age, but other tumors (and tumors outside women of reproductive age) are rare. The response to immune therapy is generally good, particularly if the more effective treatments are used promptly. However, treatment may take many months to reach its full effects, and some patients have persistent deficits, especially in the domains of memory and cognition. The mechanisms of NMDAR antibodies have been extensively studied: these antibodies cross-link and internalize the target receptors, depleting NMDARs from synapses. The antibodies are clearly directly pathogenic; passive transfer into the brains of rodents produced neurological symptoms that correlate with reduction in surface NMDARs on neurons.

Anti-LGI1 (Leucine-rich, glioma-inactivated 1) encephalitis accounts for most cases of encephalitis previously attributed to VGKC antibodies (The VGKC test, as described above, detects most LGI1 cases and also most Caspr2 cases). Myoclonus, hyponatremia, and fascio-brachial dystonic seizures are common. In some cases fascio-brachial dystonic seizures precede other symptoms of the disease by months. These seizures have characteristic appearance and respond well to immune therapy. Respiratory failure and critical illness are less common with LGI1 than NMDAR antibodies, but the course may be slower. The median age is about 60 years, significantly older than anti-NMDAR encephalitis. LGI1 is a secreted synaptic protein that organizes AMPA receptors and VGKCs at CNS synapses. LGI1 antibodies have been shown to affect AMPA receptor localization on cultured neurons, but additional mechanisms involving the localization of potassium channels are also possible. Cancers are relatively rare in this disorder, and some of these may be chance events in this older age group.

Anti-Caspr2 (contactin-associated protein-like 2) associate with encephalitis, Morvan syndrome and acquired neuromyotonia (Isaacs syndrome). The most common phenotype is Morvan syndrome, but peripheral nerve symptoms may precede or follow encephalitis by months or years. Encephalitis tends to be slower in onset than anti-NMDAR encephalitis, and responds to immune therapy but is prone to relapse with taper of immune therapy. Some patients may have thymoma and this subgroup is particularly prone to comorbid myasthenia gravis and other autoimmunities found in thymoma patients. The median age is about 60 years, significantly older than anti-NMDAR encephalitis. Caspr2 is a cell adhesion molecule that organizes VGKCs at the juxtaparanodes of myelinated axons in the central and peripheral nervous system. It is unknown why some patients have CNS versus peripheral nerve symptoms since the antigen is the same on both types of axons.

Anti-AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor encephalitis may have psychiatric symptoms on presentation like anti-NMDAR encephalitis. AMPA receptors are a widely expressed type of glutamate ionotropic receptors used for much of the rapid excitatory transmission in the brain. There is significant risk of tumors of the lung, breast, and thymus in these patients. Most patients are female and they are mostly middle-aged and older.

Anti-GABA-B (γ-Aminobutyric acid B) receptor encephalitis is characterized by encephalitis with severe seizures or status epilepticus. This is logical due to the inhibitory role of the GABA-B receptor system in the brain (GABA-B receptors are important for limiting excessive neuronal activity). About half of patients have small cell lung cancer and the patients are mostly older adults. Antibodies to the GABA-B receptor may be the most common type of immune cause found in patients with lung cancer.

Anti-GABA-A (γ-Aminobutyric acid A) receptor encephalitis has been reported in children and adults. At high titer these antibodies, which target the primary inhibitory ionotropic receptor in the brain, associate with severe encephalitis with status epilepticus or epilepsia partialis continua. So far only 1 of 6 patients had a tumor, Hodgkin lymphoma, but the full cancer associations will become clearer as more cases are found.

Anti-mGluR1 (metabotropic glutamate receptor 1) have been reported in a small number of patients with paraneoplastic cerebellar degeneration. There is a high risk of Hodgkin lymphoma in these patients. Similarly, antibodies to Homer-3, which organizes mGluR1 at synapses, have been reported in a single patient.

Anti-DNER (delta/notch-like epidermal growth factor-related receptor) target a transmembrane protein expressed on Purkinje neurons and associate with cerebellar degeneration and a very high risk (90%) of Hodgkin lymphoma. Before the precise definition of the antigen, these antibodies were referred to as "anti-Tr" and often classified with the conventional paraneoplastic disorders. Patients should be carefully and repeated screened for Hodgkin lymphoma. Even with successful tumor treatment there is often permanent cerebellar injury.

Anti-DPPX (dipeptidyl-peptidase-like protein-6) associate with a syndrome of gastrointestinal and nervous system hyper-excitability. In addition to memory loss, seizures, and confusion, symptoms of exaggerated startle, myoclonus, rigidity and hyper-reflexia have been reported. Patients may have severe diarrhea or alternatively have constipation. A small group of these patients may have tumors such as lymphoma.

Autoantibodies to intracellular synaptic proteins

Autoantibodies to intracellular antigens

Anti-Hu (ANNA-1) was the first type of onconeuronal antibody described. Patients with anti-Hu most often have sensory-predominant neuronopathy but may also or alternatively have cerebellar degeneration, encephalitis or encephalomyelitis. Multifocal involvement is common. The antibodies target a family of intracellular proteins. These antibodies are not directly pathogenic and do not cause disease in active immunization or passive transfer animal models. Pathology studies show CD8 positive T-cell infiltrates in affected tissues. The association with small cell lung cancer is very strong (approximately 86% in one series) and outcomes are often poor.

Anti-Ri (ANNA-2) associate with diverse syndromes including cerebellar degeneration and encephalitis. Most patients have lung or breast cancers.

ANNA-3 have only rarely been described and the clinical features are multifocal and have a similar range as anti-Hu.

Anti-Yo (PCA-1) are found in women with breast or ovarian cancers in more than 90% of cases. Patients usually have paraneoplastic cerebellar degeneration. Approximately half of patients die of their tumors, and tumors are often only detected after identification of the paraneoplastic disorder. There is some evidence that the antibodies may enter neurons, but other researchers think T-cell mechanisms are more likely.

PCA-2 have only rarely been reported and may associate with encephalitis or cerebellar syndromes.

Anti-CRMP-5 have diverse associations including cognitive impairment, cerebellar syndromes, abnormal movements (chorea), and cranial neuropathies. Optic neuritis has also been reported.

Anti-Ma2 (PMNA-2) are found most often in young men with germ cell tumors. Neurological symptoms could include encephalitis, cerebellar degeneration, or neuropathy. Limbic and/or brainstem syndromes may be most common.

Treatment for suspected autoimmune encephalitis is often given empirically prior to specific antibody test results. This may include steroids and/or IVIG. If a cell-surface/synaptic antibody disorder is diagnosed, initial treatments may include IVIG, plasmapheresis, and/or steroids. Steroids may be beneficial in a range of autoimmune disorders but could potentially create problems with the diagnosis of certain disorders such as CNS lymphoma. IVIG offers an important advantage of being unlikely to make infectious encephalitis worse. Plasmapheresis is also unlikely to significantly worsen infectious encephalitis.

If a synaptic/cell-surface antibody is detected and the patient has any significant symptoms, first-line therapy should be given if it has not already been tried. In general, prompt treatment, and escalation of treatment in patients who remain ill, is associated with better outcomes. Although there are not randomized treatment trials, protocols have been proposed for anti-NMDAR encephalitis, and these approaches have been applied to other diseases in the cell-surface/synaptic autoantibody category. Our group often uses IV solumedrol (1 gram daily for 3-5 days then a taper over several weeks) and IVIg (0.4 g/kg/day for 5 days). Other groups have advocated plasmapheresis instead of IVIg, and so far there is not convincing evidence of superiority for either approach.

If the patient remains significantly impaired after first-line therapy, second-line treatments are typically used. Some groups might wait 2 weeks or longer to allow first-line therapies time to work, but our group often proceeds more quickly to second line therapy sooner is patients who are very ill, for instance comatose patients with anti-NMDAR encephalitis. Second line therapies include rituximab (often 375 mg/m ² weekly for 4 weeks) or cyclophosphamide (750 mg/m ² IV monthly until improvement is noted), or both. Rituximab is a monoclonal antibody targeting CD20, so plasmapheresis generally should not be done after it is administered. Rituximab depletes CD19+/CD20+ B-cells, and circulating levels of these cells typically become undetectable for several months after treatment. Due to its relatively favorable safety profile, rituximab is more often used as monotherapy in children. Rituximab is thought to be generally effective against neurological diseases where the autoantibodies are of the IgG4 subtype. Since IgG4 responses predominate in LGI1 and Caspr2 encephalitis this provides an additional theoretical support for using rituximab in those diseases. Cyclophosphamide has several important toxicities, including a risk of infertility, especially in young women who received repeated doses (The risk cumulatively increases, potentially up to 40% after 12 doses). This risk be can reduced with use of a GnRH agonist in women, or addressed with egg/sperm collection.

Anti-NMDAR encephalitis is by far the most common type of antibody-mediated encephalitis in children. The age distribution of other types of synaptic autoimmune disorders either skews much older (the median age for LGI1 or Caspr2 antibodies is about 60 years) or the disorders are much less common (GABA-A antibodies) or both. In a study by the California encephalitis project, anti-NMDAR encephalitis was more common any single viral etiology.

Anti-NMDAR encephalitis in children may present differently than in adults. Children are more likely to have abnormal movements (chorea, incoordination) early in the disease course and also may have atypical motor symptoms such as ataxia or hemiparesis. Children more often have seizures than adults. The classic symptoms of psychosis seen in adults are less common, but behavioral regression is frequently noted. Patients may have prominent speech difficulties. Treatment strategies are similar in children and adults, but physicians may be more reluctant to use cyclophosphamide, relying more on rituximab as a second line treatment (As with adults, the optimal treatment strategies are not known). Responses to treatment are similar in children and adults, with about half failing first line therapies. Ovarian teratoma is less likely in female children before puberty, so tumors are uncommon in young children.

Patients with encephalitis may recover, completely or partially, and then experience worsening symptoms. In autoimmune encephalitis, relapse tends to follow a similar clinical course to the initial attack. In anti-NMDAR encephalitis, these relapse tend to be milder than the initial attack and manifest with confusion, worsening memory, personality change, hallucinations or new seizures (In my experience, seizures in my cases of autoimmune encephalitis remit with appropriate treatment, and new seizure should always raise concern for relapse). The risk of relapse in anti-NMDAR encephalitis in approximately 12% over two years (but continues beyond that) and is highest in untreated patients, intermediate in patients who had only first-line therapy, and lowest in patients treated with second-line therapies. Relapsed patients are usually treated with second-line therapies, possibly after first line therapies. These patients may be treated for longer periods of time with second line therapy, especially rituximab, but the optimal duration of treatment has not been established. In other types of autoimmune encephalitis, the risk of relapse is less clearly established. LGI1 antibodies and Caspr2 antibodies may associate with milder encephalitis, compared with NMDAR antibodies, than is chronic or relapsing. Similar treatment strategies may be used with these antibodies.

An important recent advance has been the recognition that patients with HSV encephalitis may rarely develop anti-NMDAR encephalitis several weeks later as a post-infectious complication. In these patients CSF from the initial attack has no NMDAR antibodies with positive PCR for HSV, but CSF from the second attack now has NMDAR antibodies with negative PCR for HSV. This phenomenon may be due to exposure of CNS antigens to the immune system in the presence of a powerful infectious stimulus. Patients who worsen after infectious encephalitis should therefore be carefully evaluated for both infectious and autoimmune etiologies. Similarly, patients who have been treated for autoimmune encephalitis may be immunosuppressed and at risk for diverse infections. However, opportunistic CNS infections after autoimmune encephalitis are probably very rare compared to worsening of the autoimmune disease.

The proper diagnosis and management of autoimmune encephalitis requires an organized approach. Evaluation should begin with a detailed history and physical examination to detect clues to specific causes. A diverse range of infections should be considered, and appropriate testing should be done to exclude relevant pathogens. Ancillary testing with MRI, EEG, and lumbar puncture may further support a diagnosis of encephalitis and potentially suggest particular causes. A broad group of autoantibody tests may be used to diagnose or exclude particular autoimmune causes, but these tests are complex and not every positive result is definite evidence of an autoimmune disorder. The risk of neoplasm should always be considered during initial treatment and follow-up visits, both in terms of diagnosing serious cancers and because specific tumors may suggest particular autoimmune causes. Treatment should depend on the pathophysiology of the disorder (e.g., T-cell-mediated or antibody mediated) and the clinical situation of the patient. Patients may relapse and should receive appropriate follow-up care from a physician familiar with the diseases.

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The Diagnosis and Treatment of Autoimmune Encephalitis

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Autoimmune encephalitis is a difficult clinical diagnosis due to the similarities in the clinical, imaging and laboratory findings of many forms of autoimmune and infectious encephalitis. Patients generally have impaired memory and cognition over a period of days or weeks. There may be clues to specific causes on history of physical examination, but often these specific signs are absent.

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Antibodies in AE can attack various antigen targets:

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Antibodies in AE can attack various antigen targets:

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NMDA, AMPA, GABA, Glycine,  and Dopamine-2,  receptors

LGI1, Caspr2, DPPX, mGluR5, mGluR1, Amphiphysin, GAD

These antigen targets are cell-surface or synaptic proteins found in the brain and spinal cord.

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Early Diagnosis and Treatment can lead to full recovery

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Early Diagnosis and Treatment can lead to full recovery

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7 patients presenting with AE in this study were promptly diagnosed with specific subsets of AE. Their prompt diagnosis and treatment led to largely successful recoveries. Interestingly, most patients with AE have complete loss of memory from the worst weeks of their time with the disease.

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Abstract

Anti-N-methyl-d-aspartate-receptor (NMDAR) encephalitis is an uncommon autoimmune disorder with a wide spectrum of neuropsychiatric symptoms. There is a great requirement to emphasize the importance of a multidisciplinary team approach in the process of diagnosis and treatment of the potentially fatal condition, including psychiatrists, neurologists, gynaecologists and intensivists. Physicians must be aware that psychiatric and neurological disorders, which are typical features for NMDAR encephalitis in young women with ovarian tumours, may progress into status epilepticus and respiratory insufficiency. This disease can only be successfully treated with prompt surgical intervention and an early implementation of a wide array of immunosuppressive therapies. Optimal timing of initiation of therapeutic plasma exchange, as well as duration of treatment necessary to achieve desirable outcomes in patients with NMDAR remains unknown. The present case report aims to raise awareness about the importance of early implementation of this potentially life-saving therapy and continuing the treatment courses until full subsidence of symptoms.

Keywords: anti-NMDA receptor antibodies, autoimmune encephalitis, therapeutic plasma exchange, status epilepticus, EEG abnormalities

Introduction

Anti-N-methyl-D-aspartate-receptor (NMDAR) encephalitis is an autoimmune disorder with a wide spectrum of neuropsychiatric symptoms, which was first described in 2005 by Vitalini et al ( 1). It has recently been demonstrated that this potentially fatal disease is significantly underdiagnosed and may contribute to the majority of cases of non-infectious encephalitis of previously unknown aetiology ( 2). Vitalini et al ( 1) retrospectively analysed >500 cases of intensive care unit (ICU) admission and identified 7 patients with encephalitic signs (psychiatric and cognitive disturbances, as well as focal or generalized seizures progressing into status epilepticus), cerebrospinal fluid (CSF) inflammation and exclusion of bacterial or viral infection, and in 6 cases the presence of anti-NMDAR antibodies was confirmed. A positive serum or CSF sample screening for antibodies to the NMDAR subunit remains the gold-standard in diagnosing the disease and must be performed in all patients presenting with an acute onset of psychiatric symptoms with atypical features or unusual movements. However, emerging data exists to suggest that electroencephalograms (EEG) can also be very useful in aiding clinicians to diagnose anti-NMDAR encephalitis ( 3).

Over the past years, increasing awareness of autoimmune mediated forms of encephalitis with antibodies against neuronal surface antigens have led to an improvement in prognosis, predominantly due to wider application of immunomodulatory therapies. Notably, despite major progress in understanding the pathophysiology of anti-NMDAR encephalitis, there remains a clear requirement for a good quality data regarding the optimal treatment of the disease, predominantly since the type of immunotherapy that is most effective in controlling the symptoms of the disease remains a matter of debate. Numerous patients, particularly with a prolonged or severe form of the disease, do not respond to first-line immunotherapy [steroids or intravenous immunoglobulins (IVIg)] and may require therapeutic plasma exchange (TPE), which is commonly used to treat a number of neurological conditions, including Guillain-Barré syndrome, myasthenia gravis, chronic inflammatory demyelinating polyneuropathy, Lambert-Eaton syndrome, multiple sclerosis, neuromyelitis optica, paraproteinemic polyneuropathy, Sydenham's chorea and natalizumab-associated progressive multifocal leukoencephalopathy ( 4). Despite the increasing number of potential indications for TPE in the treatment of neurological disorders, the proven efficacy, side effects and costs must be taken into consideration prior to a decision being made to implement this therapy.

Case report

A 23-year-old female was admitted to a psychiatric ward, presenting with acute confusion, agitation and behavioural changes. The initial diagnosis was the first episode of schizophrenia or schizoaffective disorder. Her past medical history was non-significant and no prior psychiatric or psychological problems were reported. An episode of an upper respiratory tract infection, which preceded the psychotic symptoms by few days was notable. Upon admission, agitation and restlessness were observed, followed by progressive mutism and somnolence, which were the predominant symptoms of the disease within 5 days. The patient was administered standard antipsychotic treatment during her entire stay in the psychiatric ward, which included haloperidol, olanzapine and aposulpiryd, without any improvement in her psychiatric condition. On day 5, the patient's neurological condition significantly deteriorated; decreased level of consciousness and loss of muscle tone were observed. Involuntary movements of upper limbs, jaw and eyes were also noticed, as well as clonic seizures, which were treated with intravenous diazepam. The initial diagnosis was changed to infectious encephalitis and the patient was transferred to a neurological ward at the state hospital, where CSF and blood samples were obtained and imaging studies of the brain, as well as EEG were performed ().

Results of the CSF analysis revealed a lymphocytic pleocytosis (60 white cells/µl), a normal protein level (28.3 mg/dl; normal value range: 15-45 mg/dl) and a normal glucose level (81 mg/dl). EEG recordings revealed generalized rhythmic delta activity with superimposed rhythmic beta frequency activity ('extreme delta brush') ( 5). Computed tomography (CT) of the head revealed no pathological changes. The magnetic resonance imaging (MRI), which was performed upon admission to the neurological ward, revealed only two hyperintense lesions in subcortical white matter in the frontal lobes on T2/FLAIR. Additionally, initial focal seizures evolved into generalized tonic-clonic repetitive seizures, which did not respond to various anticonvulsants, including clonazepam, sodium valproate, phenytoin and carbamazepine. Subsequently, treatment with acyclovir was initiated for presumptive viral encephalitis. Immunotherapy was also implemented and the patient received a daily dose of 20 g of IVIg for 3 consecutive days. The CSF antibody tests were negative for Epstein-Barr virus, cytomegalovirus, human immunodeficiency virus, herpes simplex virus and varicella-zoster virus. The patient's condition deteriorated further; she developed a refractory status epilepticus with concomitant respiratory failure and autonomic instability and was referred to a tertiary ICU on the 27th day of hospitalization.

The clinical course and the treatment protocol are summarized in . Upon admission to the ICU, the patient was comatose with a Glasgow Coma Scale (GCS) score of 6. Neurological examination revealed that the patient exhibited spontaneous and provoked involuntary movements of the eyes, jaw, and upper and lower limbs, despite receiving a constant infusion of clonazepam and thiopental. Excessive salivation was also noted. The patient's trachea was intubated and mechanical ventilation was initiated. Sedatives (propofol, midazolam) and opioids (remifentanil) were given in continuous infusion to facilitate mechanical ventilation, yet orofacial and limb dyskinesia were still present and difficult to control despite increasing infusion rates of propofol and midazolam. The subsequently obtained test results of CSF and blood were irrelevant with only slightly elevated white bloodcell count. Results of both blood and CSF cultures remained negative, and repeated CT scan of the brain was also normal. Since the infectious background of the disease was unable to be confirmed, autoimmunological encephalitis was suspected and high dose corticosteroids (methyloprednisolone 1 g daily for 6 days, followed by prednisone 40 mg twice daily) were administered, without any improvement in the patient's neurological status. On the 7th day of her stay in the ICU, a CT scan of the abdomen and the pelvis revealed an ovarian cyst. Additionally, a transvaginal ultrasound confirmed a left ovarian mass suggestive of a teratoma. Laparoscopic oophorectomy was immediately performed. The blood and CSF samples were collected to search for neuronal surface antibodies and the anti-NMDAR antibodies were identified in the CSF (titers, 1:3.2), but not in the plasma. The diagnosis of anti-NMDAR encephalitis was made based on the above results. Two days later, on the 36th day of hospitalization, TPE was initiated and after the third course, the patient's neurological condition markedly improved (an increase of GCS score from 6 to 11). She gradually started to open her eyes, obey simple commands and answer uncomplicated questions. Additionally, involuntary movements disappeared, yet salivation, autonomic instability and muscle weakness were still observed. The courses of TPE were continued to a total of 13 courses during her stay in the ICU. Meanwhile, another course of supplementary immunotherapy with IVIg (20 g every second day) was implemented due to its proven position as a first line treatment in the armamentarium against autoimmunological encephalitis. The relatively high frequency of TPE resulted in haemodynamic instability and coagulopathy, which required plasma transfusion; therefore, the intervals between TPE were increased from 1 to 3 days and the anticoagulant was changed from unfractionated heparin to citrate. The autonomic dysfunction persisted despite obvious improvement in cognitive status and involved severe bradycardia and hypersalivation, which made all the tracheal extubation efforts futile. Therefore, on the 25th day of the ICU stay, a tracheostomy was performed. The patient was subsequently weaned from mechanical ventilation and transferred to a neurological ward to continue intensive rehabilitation. She was discharged in a good clinical condition nearly 3 months after the onset of the disease. The follow-up assessment was performed 3 months following discharge. The patient's neurological state was tested with modified Rankin Scale (mRS) and she gained 1 point. She reported no significant disability and was able to perform all usual activities. The only neurological sequel included parasomnia and complete loss of memory during the entire hospitalization period.

Discussion

The present case study described a clinical course of anti-NMDAR encephalitis, which is one of the central nervous system (CNS) diseases, where the presence of the neuronal surface antibodies can be demonstrated ( 6). This relatively uncommon disorder has a typical sequential presentation: sudden onset with prodromal, fever-like symptoms, followed by a psychiatric disorders, decreased level of conscious accompanied by intractable focal and clonic seizures, dyskinesias and autonomic instability ( 7). In the present case, all of the above-mentioned symptoms were observed, so the clinical course of the anti-NMDAR encephalitis was typical. In addition, the patient was a young female, which is also a common feature of this type of autoimmunological encephalitis, since this patient population accounts for ~80% of reported cases ( 8). Furthermore, the coexistence of an ovarian tumour, which was confirmed to be a teratoma in this case, is also a typical for anti-NMDAR encephalitis. This type of encephalitis is suggested to be strongly associated with malignancies, including ovarian, mediastinal and testicular teratomas, Hodgkin's lymphoma, small cell lung carcinoma, and neuroblastomas. However, more recent studies have challenged these data showing that up to 80% of patients may present with a non-paraneoplastic type of the disease, making the diagnosis even more difficult ( 9). When anti-NMDAR is suspected the diagnostic tests typically include detection of NMDAR autoantibodies in CSF and/or in the serum as the core of diagnosis, predominantly because other laboratory tests and imaging studies of the brain appear to be irrelevant ( 10, 11). On the other hand, MRI scans of the patient's CNS revealed multifocal subcortical white matter lesions in T2/FLAIR, which were also described by other authors and may be concomitant with anti-NMDAR encephalitis ( 9).

There is ongoing debate as to whether serum or CSF must be tested for in the presence of anti-NMDAR antibodies. In the present case, high levels of anti-NMDAR antibodies were detected in the CSF, but not in the plasma. The association between the prodromal flu-like symptoms and the antibodies against NMDAR is also a matter of debate. Certain authors emphasise the connection between a viral infection and damage of the blood-brain-barrier, which facilitates transfer of NMDAR autoantibodies to the CNS, whilst others claim that flu-like symptoms are only a part of an early immunological activation ( 12). Nevertheless, when anti-NMDAR encephalitis is suspected it appears absolutely crucial to search for the antibodies in both serum and CSF, yet other more readily available diagnostic measures must also be implemented in order to obtain the final diagnosis. In the present case, a retrospective analysis of the first EEG recordings revealed an unique electrographic pattern, which is referred to as "extreme delta brush", due to of its resemblance to waveforms observed in premature infants ( 13). Although the specificity of this finding remains unclear, its presence is usually associated with a more prolonged and severe course of illness. An EEG maybe extremely valuable in distinguishing between encephalitis and a primary psychiatric disorder, since a vast majority of patients with anti-NMDAR encephalitis exhibit a non-specific slowing at a certain stage during the illness. In addition, characteristic pattern of generalized rhythmic delta activity with superimposed rhythmic beta frequency activity may appear, which was described in a large series of patients unique to this disorder ( 8).

Treatment of anti-NMDAR encephalitis remains challenging, since no comprehensive guidelines have been published to date. The majority of authors agree that treatment must target both the cause and the clinical consequences of the encephalitis. It is generally accepted that the anti-NMDAR encephalitis treatment is much more effective in patients who have an underlying tumour removed and there are numerous cases described in which ovarian teratomas were discovered years after initial onset of symptoms, particularly in patients who experienced a slow recovery ( 14). Certain authors advocate early oophorectomy even in cases when the presence of an ovarian tumour cannot be confirmed in imaging studies. In a case described by Peery et al ( 14), postoperative biopsy revealed an occult teratoma, and the surgical removal of the tumour resulted in an improvement of clinical symptoms. In the majority of cases, immunotherapy is the first-line treatment and typically includes corticosteroids, IVIg and TPE, administered alone or in combination ( 15). The second-line treatment includes rituximab and cyclophosphamide, and is used predominantly in patients who either exhibit a delayed diagnosis or did not have an underlying malignancy ( 16). It is worth mentioning that the role of specific treatment options remains a matter of debate and numerous authors provide conflicting data on the subject, with special regards to the role of TPE, which in the opinion of Dalmau et al ( 17) should not be used routinely. On the other hand, numerous recently published case studies, where implementation of TPE was associated with an improvement of clinical status, exist ( 18, 19). In a recent paper published by DeSena et al ( 20), the efficacy of intravenous methylprednisolone administered alone or following TPE was compared in the treatment of anti-NMDAR receptor encephalitis. The obtained results were clearly in favour of administering steroids only after TPE was performed in the studied patient population.

In the present case, the patient was initially treated in the neurological ward with the use of corticosteroids (methylprednisolone) and IVIg due to suspected infectious encephalitis. This first-line immunosuppressive treatment failed to produce any improvement of the patient's clinical condition. Similarly, the second course of high-dose corticosteroids administered in the ICU was not effective. The patient's clinical condition only improved following the third course of TPE, which is in line with the case study published by Nunez-Enamorado et al ( 21). By contrast, clinical improvement in cases of anti-NMDAR encephalitis is not always achieved with TPE ( 22, 23). According to the guidelines published by the American Society for Apheresis, the use of TPE must be considered as a third-line treatment in paraneoplastic neurological syndromes (grade 2C) ( 24).

In conclusion, NMDAR encephalitis is a potentially reversible disorder with a good clinical outcome if diagnosed and treated promptly. A multimodal immunosuppresive therapy may result in an improvement in neurological symptoms in >60% of patients ( 25). In the present case, a long-term follow-up examination revealed a good clinical outcome, without any major neurological or psychiatric complications following the anti-NMDAR encephalitis. A multidisciplinary team, including psychiatrists, neurologists and intensivists, must be involved in the process of recognition and management of the disease. The gold standard for diagnosing anti-NMDAR encephalitis is still detecting the antibodies in either the CSF or plasma; however, other diagnostic measures, including EEG or MRI may also aid clinicians in obtaining the final diagnosis. Tumour removal and pharmacotherapy remain the first-line treatment in the majority of cases, yet TPE must also be considered in the clinician's armamentarium, particularly in cases where initial treatment has failed. Available data remains ambiguous and therefore there remains an urgency for good quality clinical trials.

References

11. Motta E, Gołba A, Kazibutowska Z, Huć M, Stęposz A. Anti-NMDA receptor encephalitis-case report. Neurol Neurochir Pol. 2012;46:288-293. (In Polish) [[ PubMed] Google Scholar]

18. Zhang Y, Gao D, Ye H, Su Y. [Safety of plasma exchange therapy in patients with anti-NMDA receptor encephalitis. Zhonghua Yi Xue Za Zhi. 2015;95:1505-1508. (In Chinese) [[ PubMed] Google Scholar]

21. Nunez-Enamorado N, Camacho-Salas A, Belda-Hofheinz S, Cordero-Castro C, Simon-De Las Heras R, Saiz-Diaz R, Martinez-Sarries FJ, Martinez-Menendez B, Graus F. Fast and spectacular clinical response to plasmapheresis in a paediatric case of anti-NMDA encephalitis. Rev Neurol. 2012;54:420-424. (In Spanish) [[ PubMed] Google Scholar]

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Successful treatment of anti-NMDA receptor encephalitis with a prompt ovarian tumour removal and prolonged course of plasmapheresis: A case report

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Anti-N-methyl-d-aspartate-receptor (NMDAR) encephalitis is an uncommon autoimmune disorder with a wide spectrum of neuropsychiatric symptoms. There is a great requirement to emphasize the importance of a multidisciplinary team approach in the process of diagnosis and treatment of the potentially fatal condition, including psychiatrists, neurologists, gynaecologists and intensivists.

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In 2015 the death of a world famous polar bear, Knut from the Berlin Zoo, was attributed to anti-NMDAR AE. This case suggests that this disease is not specific to only humans but occurs in other mammals. While encephalitis has been found to occur in animals and can be treated, autoimmune encephalitis is a relatively new finding that constitutes alternative treatments.

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Abstract

Knut the polar bear of the Berlin Zoological Garden drowned in 2011 following seizures and was diagnosed as having suffered encephalitis of unknown etiology after exhaustive pathogen screening. Using the diagnostic criteria applied to human patients, we demonstrate that Knut's encephalitis is almost identical to anti-NMDA receptor encephalitis which is a severe autoimmune disease representing the most common non-infectious encephalitis in humans. High concentrations of antibodies specific against the NR1 subunit of the NMDA receptor were detected in Knut's cerebrospinal fluid. Histological examination demonstrated very similar patterns of plasma cell infiltration and minimal neuronal loss in affected brain areas. We conclude that Knut suffered anti-NMDA receptor encephalitis making his the first reported non-human case of this treatable disease. The results suggest that anti-NMDA receptor encephalitis may be a disease of broad relevance to mammals that until now has remained undiagnosed.

Rarely has an animal gained as much worldwide attention during its lifetime as the polar bear ( Ursus maritimus) Knut, born 2006 in the Berlin Zoological Garden. Knut's popularity resulted in the most profitable period in the Zoo's 163-year history. In 2011 in front of running cameras, Knut drowned after he suffered epileptic seizures and fell into the enclosure's pool. Pathological analyses revealed that Knut suffered encephalitis which caused the seizures. An exceptionally extensive investigation for infectious causes for a single animal failed to demonstrate a bacterial, viral or parasitic cause for the encephalitis. Highly detailed pathological investigations, histology, extensive serology, thirty five pan-PCR assays, two pathogen microarray systems, and shotgun sequencing on both the GSF FLX and Illumina HiSeq systems only revealed a serological response to influenza A and a novel endogenous retroviral group, neither of which would have been responsible for Knut's symptoms. Thus, a diagnosis of "encephalitis of unknown etiology" was established.

In human patients it has become clear since 2010 that the vast majority of patients with encephalitis of unknown etiology, after exclusion of infectious causes, results from an autoimmune disease called anti-NMDA receptor (NMDAR) encephalitis. It is a severe disease associated with highly specific autoantibodies against the NR1 subunit of the NMDA type glutamate receptor. It follows a specific multistep clinical pattern starting with prodromal signs (such as headache, nausea, low-grade fever) and psychosis (hallucinations, delusions, suicidal thoughts) progressing to epileptic seizures, reduced levels of consciousness, dyskinesias, autonomic dysfunction and hypoventilation. Within a few years since its discovery, more than 1000 patients have been described, making it a more common disease than other encephalitides, such as herpes simplex virus encephalitis. The discovery has revolutionized the field of modern clinical neurology. However, while another form of anti-receptor autoimmunity with LGI1 antibodies has been observed recently in domestic cats, the more common anti-NMDAR encephalitis has only been considered a human disease leaving open the possibility that an entire field of encephalitis relevant research has gone unexplored in domestic and wild animals.

Prior to the identification of NMDAR antibodies, human patients with this characteristic disease were often diagnosed with encephalitis of unknown etiology and thus, we tested the hypothesis that Knut's encephalitis may have been caused by NMDAR antibodies which would make his the first diagnosed non-human case and suggest that anti-NMDAR encephalitis is a general disease of mammals.

Results

Autopsy demonstrated encephalitis

The brain was removed () and analyzed by histology. H&E stained sections of brainstem and cerebrum demonstrate a patchy distribution of infiltrating immune cells among normal brain tissue (). In some areas, pronounced inflammation was detected with inflammatory infiltrates transmigrating from small brain vessels into the parenchyma, although the density of immune cells was lower than observed in infectious encephalitis (). The cells were not clustered in the vessel wall as in vasculitis. In a normal polar bear, the brain parenchyma lacks immune cells, as shown on sections of a male polar bear that died after foreign body ingestion (). In healthy and inflamed brain areas, the neurons were largely intact, arguing for a disease mechanism that did not primarily depend on cytotoxic T-cells (). Instead, numerous plasma cells were detected around vessels and within the parenchymal infiltrates (, arrows). Although the plasma cells do not always have the appearance expected for human patients, they are nearly identical to plasma cells observed in other carnivores such as dogs. Unspecific reactive gliosis was demonstrated with immunostaining of GFAP (). Apart from the brain, no obvious abnormalities were detected in other organs and no tumors were detected at necropsy.

Polar bear NMDA receptor homology

Sequence analysis of the human NR1 subunit of the NMDA receptor showed very high homology with portions of the polar bear genome scaffold 203, in particular in the amino terminal extracellular region of the protein containing amino acid N368, which is known to represent the major epitope in anti-NMDAR encephalitis ().

Knut's CSF contains very high levels of NMDAR autoantibodies

The gold standard for testing patients for the presence of NMDAR autoantibodies is the combined use of tissue immunohistochemistry and cell-based assays in which the protein of interest is transiently expressed in HEK cells. Therefore HEK cells were transfected with GRIN1 cloned into the pBudCE4.1 vector. Cells expressed high levels of NMDAR protein, in contrast with control cells transfected with the vector only. Due to the lack of anti-polar bear secondary antibodies, we used two independent strategies to label CSF immunoglobulins. First, Knut's CSF was incubated with FITC-tagged protein A. Second, the antibodies were covalently bound to Alexa-594. Both, the protein A-based assay () and the Alexa coupling () showed identical results with strong binding to HEK cells expressing the NMDAR, were double-positive with commercial anti-NR1 antibodies, and absent on untransfected cells. Antibody titers were very high, i.e. a positive signal was still detectable when diluting the initial CSF concentration by more than 1:1,000, thus exceeding the CSF antibody titers seen in many patients with anti-NMDAR encephalitis.

Both stainings were verified on Euroimmun BioChips with strong signal on NR1-transfected cells, but no signal on HEK cells transfected with AMPA receptors (), Caspr2 (), LGI1 (), or GABAb receptor (not shown) which are all targets in distinct forms of human autoimmune encephalitis. Thus, with five unrelated receptors tested for reactivity, only NMDAR produced a response in Knut.

Antibody binding to brain sections

Antibodies from patients with anti-NMDAR encephalitis are known to strongly bind to rat brain sections, particularly in cortical, hippocampal and cerebellar areas. Knut's antibodies exhibited an identical labeling pattern as human patients () showing intense labeling of rat hippocampus and cerebellum, such as in the cerebellar granule cell layer () or hippocampal neuropil (). CSF from the male polar bear (which died of foreign body ingestion) for which histology was compared to Knut was not available. However, CSF from a second polar bear, Nancy, which died of gastric torsion, did not react at all with rat hippocampus () and cerebellum demonstrating reactivity was unique to Knut. As observed in human patients, NMDAR antibodies stain broadly in the hippocampus. Knut's pattern was very similar to previously reported anti-NMDAR encephalitis cases or to experimental staining performed in the current study (, insert shows staining on mouse brain). However, we did observe a difference in staining in the hilum of hippocampus which exhibited reduced staining with Knut's CSF but staining nonetheless. Human CSF produced less staining in our experiments and has been reported not to bind to this brain region in humans. One possible explanation is that in addition to NMDAR antibodies, another anti-receptor antibody is present in Knut's CSF. However, if this is the case, it would represent a minor component as NMDAR antibody concentrations were very high, staining was reduced in hilum and it would not represent one of the common human encephalitis antibodies as we excluded antibodies against AMPA receptors, Caspr2, LGI1, and GABAb receptor (). Another likely explanation for the observed pattern is species-specific differences in NMDAR binding by polar bears antibodies. Further molecular immunological studies on polar bears will be needed to clarify this point. We further tested whether Knut's antibodies bind to his own cerebellum. Indeed, strong staining was detectable in the large fiber tracts of the cerebellum with an axonal distribution (). As the binding pattern is slightly different to rat brain, we confirmed the specificity by using a monoclonal mouse anti-NR1 () and a polyclonal rabbit anti-NR1 antibody () which gave identical results on the polar bear brain section. CSF from polar bear Nancy showed no reaction with the tissues ().

Discussion

Prior to this study, the death of Knut represented an unsolved mystery given the lack of any pathogen detected subsequent to intensive investigation. Generally, the diagnosis of anti-NMDAR encephalitis in human patients is based on those who have (i) clinical signs of encephalitis (epileptic seizures, reduced levels of consciousness, cognitive or mood changes), (ii) evidence of brain inflammation (MRI abnormalities, CSF inflammation, or positive biopsy/autopsy), (iii) exclusion of viral/bacterial causes, and (iv) detection of CSF (+/− serum) antibodies against the NMDA receptor. Thus, the presence of seizures, inflammatory infiltrates in the brain, exclusion of an infectious etiology, and very high levels of NMDAR antibodies allow a firm diagnosis of anti-NMDAR encephalitis in Knut. The lack of symptoms and immunostaining from CSF from the control female, a polar bear which died of gastric torsion and would not be expected to have autoimmune disease, and lack of histological evidence for autoimmune disease in an unrelated male polar bear, which died after foreign body ingestion, further strengthens the argument that Knut alone exhibited characteristics of anti-NMDAR encephalitis. In addition to the antibodies, the cellular composition of inflammatory infiltrates resembles the pattern known from human patients with anti-NMDAR encephalitis, characterized by only very limited neuronal pathology and a low density of inflammatory cells. Although long term observation of Knut's epileptic syndrome was not possible, video footage taken at the time demonstrated focal seizure initiation and generalization to grand mal seizures, consistent with the epileptic syndrome in human patients. The presence of antibodies against influenza A virus in the polar bear is also a known finding in patients with anti-NMDAR encephalitis.

The direct pathogenic role of NMDAR antibodies has been verified in numerous studies demonstrating immunoglobulin-induced internalization of surface NMDARs. Recently it has been demonstrated that laboratory mice infused with CSF from anti-NMDAR encephalitis patients exhibit altered memory and behavior in addition to histopathological features of human disease demonstrating a direct role for antibody mediated loss of NMDAR and disease. As Knut's antibodies specifically bind to NMDARs and the immunostaining pattern on brain sections is nearly identical to what is seen with CSF of human anti-NMDAR encephalitis patients, we propose that the antibodies also caused the encephalitis that resulted in the polar bear's death although direct confirmation is not possible. Autoimmune encephalitides, in particular anti-NMDAR encephalitis, respond well if immunosuppressive therapy is started early and sufficiently aggressive. It is tempting to speculate that anti-NMDAR encephalitis in polar bears is similarly treatable and that had he not drowned, Knut could have survived the condition, in particular as administration of high-dose corticosteroids can be done routinely in captive animals.

Although encephalitis is common among domestic and captive wild animals, the causative agent is often undiagnosed and thus the cases remain unreported or the pathology is atypical such as lack of inclusion bodies in polar bears and rhinoceros infected with zebra equine herpesviruses. Even in cases where infectious causes are suspected, additional autoimmune mechanisms might participate in disease progression, similarly to what has been shown for the brain infection with herpes viruses and subsequent anti-NMDAR encephalitis. If confirmed, this would guide new approaches to managing encephalitis in wild and domestic animals, in particular in species with high conservation value, such as polar bears and rhinoceros.

Based on the results presented here, one could anticipate that in addition to anti-NMDAR encephalitis, other forms of autoimmune encephalitis known from humans will be discovered in wild mammals and will have to be considered in the field of zoo and wildlife medicine in the future. Knut's anti-NMDAR encephalitis suggests that antibody-mediated autoimmunity might be a far more common disease in mammals than previously thought.

Methods

Ethics Statement

The experiments undertaken in this project were approved by the Internal Ethics Committee of the Leibniz Institute for Zoo and Wildlife Research (IZW), Approval No. 2012-04-01. All experiments undertaken were in accordance with the approved guidelines. All experimental protocols were performed with the approval of the Leibniz Institute for Zoo and Wildlife Research and the Charité University Medicine Berlin.

Protein A-FITC labeling of antibodies

In contrast to protein-G, staphylococcal protein A (SP-A) is known to bind polar bear IgG. 100 μl of cerebrospinal fluid (CSF) and 50 μg FITC-conjugated SP-A (Sigma, #P5145) were incubated for 2 h in the dark at room temperature and diluted to 500 μl with PBS. The mixture was re-concentrated and unbound FITC-SP-A removed using 100 kDa Amicon filter units (Millipore).

Alexa-594 labeling of antibodies

After establishing optimal labeling conditions with CSF of patients with anti-NMDAR encephalitis, polar bear CSF was conjugated with N-Hydroxysuccinimid-ester of Alexa Fluor 594 (Life Technologies). For this step, 110 μg of Alexa-594 and 100 μl polar bear CSF were incubated for 1 h at room temperature on a shaker at 200 rpm. The sample was diluted in PBS to 500 μl and purified using Amicon columns as above.

Cell transfection and antibody detection

The cDNA of GRIN1 was kindly provided by Prof. Dr. Wanker (MDC, Berlin) and cloned into pBudCE4.1 (Life Technologies). NR1 DNA (1 μg) was mixed with 3 μg PEI and 100 μl 150 mM NaCl, vortexed and incubated for 10 min, and HEK293 cells were transiently transfected. Two days later, HEK cells on cover slips were fixed with methanol at −20 °C for 4 min. In addition, HEK cells transfected with a different NMDAR clone, leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein 2 (Caspr2), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, and gamma-aminobutyric acid b (GABAb) receptor were used (Autoimmune-Enzephalitis-Mosaik 1, Euroimmun, Lübeck, Germany). For staining with polar bear CSF, cells were washed in PBS, preincubated with 5% normal goat serum containing 2% bovine serum albumin and 0.1% Triton X-100, and incubated with CSF starting at a 1:5 dilution overnight at 4 °C. Sections were washed in PBS and coverslips mounted with Immu-Mount (ThermoScientific). No polar bear serum was available for antibody detection as blood from Knut was coagulated and autolysed as described. Double-labeling of transfected cells was performed using commercial antibodies: monoclonal mouse anti-NR1 (1:100, Synaptic Systems).

Immunohistochemistry

Paraffin-embedded bear brain sections were deparaffinated with xylene and rehydrated. Antigen retrieval was performed by boiling in 0.1 M citrate buffer pH 6 for 10 min. Rat brain sections were used after PFA fixation. Tissue was permeabilized in 0.1% Triton X-100 in PBS for 20 min and blocked in 10% normal goat serum for 30 min. Polar bear or human CSF was diluted 1:10 and sections incubated overnight at 4 °C. Further stainings included rabbit polyclonal anti-NR1 (1:100, Synaptic Systems), anti-GFAP (1:2,000; NeuroMab) anti-MAP2 (1:500, Millipore).

Sequence analysis

Using the human NMDA receptor mRNA sequences as a query, the polar bear genome was examined for genomic scaffolds containing the polar bear NMDAR ortholog. Scaffold 203 of the current polar bear genome contained a sequence with strong (>90%) identity with the human NMDA receptor. The polar bear sequence was used as a blastn query and the human genome scaffold sequence was aligned to the polar bear sequence using BioEdit version 7.0.9.

Additional Information

How to cite this article: Prüss, H. et al. Anti-NMDA Receptor Encephalitis in the Polar Bear ( Ursus maritimus) Knut. Sci. Rep. 5, 12805; doi: 10.1038/srep12805 (2015).

Acknowledgments

The authors wish to thank Karin Hönig, Doris Krumnow, Marion Biering, Doreen Lüdecke, and Tuula Geske for technical support and Dr. Kyriakos Tsangaras with assisting with the identification of the NMDA receptor from the polar bear genome. The authors also wish to thank the Berlin Zoological Garden for their support in the continuing research on Knut, specifically Dr. Andreas Knieriem, Heiner Klös and Dr. André Schüle. They also thank Dr. Gudrun Wibbelt for necropsy support in obtaining tissues from Nancy, the control polar bear. They further thank Dr. Bianca Teegen and Prof. Winfried Stöcker from Euroimmun for providing BioChip assays. Funding was provided by The German Research Foundation (DFG, PR 1274/2-1) to H.P.

Footnotes

Author Contributions H.P., C.A.S. and A.D.G. designed the study. H.P., J.L., N.K.W., C.A.S., G.A.C. and A.D.G. performed and collected data from experiment and analyzed data. H.P., J.L., N.K.W., C.A.S., G.A.C. and A.D.G. wrote the manuscript.

References

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Anti-NMDA Receptor Encephalitis in the Polar Bear (Ursus maritimus) Knut

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Knut the polar bear of the Berlin Zoological Garden drowned in 2011 following seizures and was diagnosed as having suffered encephalitis of unknown etiology after exhaustive pathogen screening. Using the diagnostic criteria applied to human patients, we demonstrate that Knut's encephalitis is almost identical to anti-NMDA receptor encephalitis which is a severe autoimmune disease representing the most common non-infectious encephalitis in humans.

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The New York Times bestselling book was recently turned into a Netflix film. Check out the trailer!

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Brain on Fire Trailer #1 (2017) Chloë Grace Moretz Drama Movie HD

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Brain on Fire Trailer 1 (2017) Chloë Grace Moretz Drama Movie HD [Official Trailer] Title: Brain on Fire Release Date: 2017 Cast: Chloë Grace Moretz, Jenny Slate, Richard Armitage, Carrie-Anne Moss, Tyler Perry, Thomas Mann

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In her autobiography Susannah Cahalan, details her first hand experience with Autoimmune Encephalitis. She was finally diagnosed with anti-NMDA receptor encephalitis after a month of violent episodes and delusions in the hospital. Many with this disease suffer from misdiagnosis for much longer. Her book is a detailed account of her recovery process.

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In 2009, Susannah Cahalan was a healthy 24-year-old reporter for the New York Post, when she began to experience numbness, paranoia, sensitivity to light and erratic behavior. Grasping for an answer, Cahalan asked herself as it was happening, "Am I just bad at my job - is that why? Is the pressure of it getting to me? Is it a new relationship?"

But Cahalan only got worse - she began to experience seizures, hallucinations, increasingly psychotic behavior and even catatonia. Her symptoms frightened family members and baffled a series of doctors.

After a monthlong hospital stay and $1 million worth of blood tests and brain scans that proved inconclusive, Cahalan was seen by Dr. Souhel Najjar, who asked her to draw a clock on a piece of paper. "I drew a circle, and I drew the numbers 1 to 12 all on the right-hand side of the clock, so the left-hand side was blank, completely blank," she tells Fresh Air's Dave Davies, "which showed him that I was experiencing left-side spatial neglect and, likely, the right side of my brain responsible for the left field of vision was inflamed."

As Najjar put it to her parents, "her brain was on fire." This discovery led to her eventual diagnosis and treatment for anti-NMDA receptor encephalitis, a rare autoimmune disease that can attack the brain. Cahalan says that doctors think the illness may account for cases of "demonic possession" throughout history.

Cahalan's new memoir is called Brain on Fire: My Month of Madness.

Interview Highlights:
On the moment when Cahalan lost her sanity
"I don't remember anything from this experience. This was all told to me after the fact. [My boyfriend] Stephen heard guttural sounds coming from me. He thought maybe I was just angry because I hadn't slept for days, and he knew that it was really frustrating. And so he thought, 'Maybe she's just venting her frustration.' But the grunts were very unnatural sounding, so he turned and looked at me. And he saw that my eyes were wide open but completely unseeing, and at that point he tried to shake me and say, 'Are you OK, Sue? What's going on?' And at that point, my arms whipped out, and I had a grand mal seizure, and I was convulsing. And I bit my tongue so that blood and kind of a combination of blood and foam was coming out of my mouth. And he had the presence of mind - and I think this is incredible - to know that this was a seizure because I had never had a seizure before. And so he turned me on my side and he called 911. And [that's, for me] ... the difference between sanity and insanity ... that moment where kind of my memory goes dark."
On some of the symptoms she exhibited at the hospital
"I slurred my words. I drooled. I didn't have proper control over my swallowing ... I kept my arms out in unnatural poses. At one point, I was like the Bride of Frankenstein - I kept my arms out rigidly. I was slow. I could hardly walk, and when I did, I needed to be supported ... I started [acting] very psychotic. I believed that I could age people with my mind. If I looked at them, wrinkles would form, and if I looked away, they would suddenly, magically get younger. And I believed that my father had murdered my stepmother. I believed all these incredibly paranoid - a huge, extreme example of persecution complex. And then as the days went on, I stopped being as psychotic, and I started entering into a catatonic stage, which was characterized by just complete lack of emotion, inability to relate, or to read, or hardly to be able to speak."
On being supported by her parents and boyfriend
"Without them, I wouldn't be here right now, especially with my mom. She was a bulldog. I mean she would not take 'no' for an answer, especially in the beginning when they were saying it was alcohol withdrawal and partying. She refused to see that as an answer, and so she did her own research. She asked questions. At home, after a day at the hospital, she'd make a list of all the different terminology they used, and she'd look it up and, you know, not everyone is capable of doing that. ... I was so lucky to have someone there for me that could do that. ... If everyone could have someone like that, it would just be a better world."
On the possible connection between her rare immune disease and cases of "demonic possession" throughout history
"When you think about the symptoms - in my case alone, this grandiosity, this violence. In a lot of children, you see hypersexuality. Even my grunts and these guttural sounds that came from me sounded superhuman to someone who might be inclined to think that way. ... When you see videos of people - in fact, when I see videos of myself - demonic possession is not far from your mind. It wasn't far from Stephen's mind when he first saw that seizure. And I've talked to many people who've had this disease, and one woman I spoke to actually asked for a priest because she said, 'The devil is inside of me. I need it out.' A little girl was grunting - they had a monitor in her room - and she was grunting so unnaturally that her parents looked at each other and said, 'Is she, is she possessed?' They actually said that about a little girl. You can see throughout history why people would believe this."

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A Young Reporter Recounts Her Descent Into Madness

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In her memoir, Susannah Cahalan writes about the month she descended into madness, experiencing seizures, paranoia, psychosis and catatonia. At first, her family was frightened, and her doctors, baffled. The eventual prognosis? A rare autoimmune disease that was attacking her brain.

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Summary of AE and Sources Used throughout this Padlet

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Summary of AE and Sources Used throughout this Padlet

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Summary of Autoimmune Encephalitis Research and Sources

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Go to aealliance.org for additional resources and information about AE

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Go to aealliance.org for additional resources and information about AE