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Early Brain Herniation Descriptions: 1829: First recorded descriptions of brain tissue displacement through the foramen magnum.

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Early Brain Herniation Descriptions: 1829: First recorded descriptions of brain tissue displacement through the foramen magnum.

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In 1829, Jean Cruveilhier documented cases of brain tissue protruding into the spinal canal. This is now recognized as Chiari Malformation. Cruveilhier did not identify this as a distinct disorder but his observation made a good framework to the future discoveries behind the disorder.

While Cruveilhier noted the herniation in the brain, the condition was unnamed. But in the late 19th century an Italian pathologist would be able to classify Chiari Malformation.

Source: https://doi.org/10.3390/anatomia2030019

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Jean Cruveilhier (1791–1874), a Predecessor of Evidence-Based Medicine

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This article focuses on Jean Cruveilhier and particularly on his book Anatomie descriptive, which was a great success during the author’s lifetime. (Notwithstanding this, it is pertinent to point out that the five editions of Anatomie descriptive were surpassed in number by others of the Cruveilhier’s creations, such as Anatomie pathologique and Traité d’Anatomie pathologique.) Unlike other texts of the time and later, Anatomie descriptive presents the anatomy of the human body in a way that can be applied both by students and medical professionals. The objectives of Anatomie descriptive were to make understand how the functions of an organ can be inferred from its structure, and to encourage students and professionals to investigate the anatomical origin of health and disease phenomena. Depending on which sections of the book, the parts of the body were described with morphological, topographic or functional criteria. Many of Cruveilhier’s contributions influenced anatomical eponymy and keep today’s Terminologia Anatomica alive. All of this has made consider Jean Cruveilhier the most outstanding anatomist in France of the first half of the nineteenth century. Due to the scientific rigor Cruveilhier always applied and asked to be applied in the investigation of the anatomic changes linked to pathological processes, he could certainly be considered a predecessor of the objectivity sought by evidence-based medicine.

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Hans Chiari's Malformation Classification: 1891: Defined Chiari Malformation as a distinct neurological disorder and introduced its classification system.

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Hans Chiari's Malformation Classification: 1891: Defined Chiari Malformation as a distinct neurological disorder and introduced its classification system.

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In 1891, Dr. Hans Chiari, studied brain specimens and categorized Chiari malformations into 3 different types based on how severe the cerebellum displacement was. His work was the first to define and differentiate the condition into 3 categories. This was a big step for future research on the topic including diagnosis and treatment.

Chiari's classifications allowed for better recognition of the disorder but the cause of the disorder was unknown. It wasn't until there were some advancements in neuroimaging and neurosurgery that researchers could fully investigate the impact of Chiari on the nervous system.

Source: https://doi.org/10.1007/s00415-010-5529-0

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Hans Chiari (1851–1916) - Journal of Neurology

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Arnold's Contribution to Chiari malformation: 1894: Expanded understanding of the condition by linking it to possible spinal cord abnormalities.

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Arnold's Contribution to Chiari malformation: 1894: Expanded understanding of the condition by linking it to possible spinal cord abnormalities.

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A German pathologist named Julius Arnold further investigated Chiari malformation, and was able to link it to spina bifida and other possible spinal cord defects. The term "Arnold Chiari Malformation" became associated with the disorder because of his work and including more severe types of the disorders of it, it was considered to be classified as Type II.

With Chiari Malformation now classified and the discovery of it possibly being linked to spinal cord abnormalities, early treatments could begin emerging. However, without the advanced imaging technology, the diagnosis of this disorder relied mainly on autopsies until neurosurgical inventions became more popular in the 20th century.

Source: https://intermountainhealthcare.org/ckr-ext/Dcmnt?ncid=520408000

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Early Neurosurgical Treatments: 1930-1950: Introduction of surgical decompression techniques to relieve pressure from herniating brain.

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Early Neurosurgical Treatments: 1930-1950: Introduction of surgical decompression techniques to relieve pressure from herniating brain.

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Before advanced imaging was developed, Chiari Malformation had to be diagnosed during an autopsy. The first surgical attempts to decompress the pressure in living patients began in the 1930s-1950s. This was when posterior fossa decompression surgery had been introduced. The goal of this method was to expand the skull opening to reduce pressure on the cerebellum and the brainstem.

While surgery provided relief for these patients, diagnosing Chiari in living patients remained pretty difficult for doctors and researchers. It wasn't until MRI technology became more popular that non-invasive, early detection was possible for these patients.

Source: https://mayfieldclinic.com/pe-chiari-surgery.htm

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Chiari decompression surgery | Mayfield Brain & Spine, Cincinnati OH

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The dura overlying the herniated tonsils is opened and a patch is sewn to expand the space, similar to letting out the waistband on a pair of pants. The goals of surgery are to control the progression of symptoms, relieve compression, and restore the normal flow of cerebrospinal fluid (CSF)

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MRI Revolution in Diagnosis: 1985: Allowed for non-invasive, visualization of Chiari Malformation, improving diagnosis and treatment planning

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MRI Revolution in Diagnosis: 1985: Allowed for non-invasive, visualization of Chiari Malformation, improving diagnosis and treatment planning

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In 1985, the introduction of the MRI transformed the ability to diagnosis Chiari Malformation. For the first time, doctors were able to visualize the cerebellar herniation in living patients rather than in an autopsy. This lead to earlier and more accurate diagnoses. This advancement improved treatment planning and the outcomes for patients greatly.

MRI allowed for better understanding of Chiari Malformation, but treatment options were still being studied. Today, modern neuroscience is still researching new approaches to managing the symptoms of Chiari and improving the outcomes to make them more favorable.

Source: https://radiopaedia.org/articles/chiari-i-malformation?lang=us

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Chiari I (Chiari 1) malformation is the most common variant of the Chiari malformations and is characterized by a caudal descent of the cerebellar tonsils through the foramen magnum. Symptoms are generally proportional to the degree of descent. MRI is the imaging modality of choice. Treatment with posterior decompression is usually reserved for symptomatic patients or those with a syrinx.

Chiari I malformations are more frequently encountered in females ¹.

Although Chiari I malformations are often isolated abnormalities, the following findings may be seen in association:

cervical cord syrinx in ~35% (range 20-56%): more common in symptomatic patients

hydrocephalus in 7-10% ¹⁴ of cases

the relationship remains poorly understood and whether the hydrocephalus or Chiari 1 malformation is the primary abnormality continues to be debated ¹²

abnormal CSF flow dynamics through the central canal of the cord and around the medulla, posterior fossa size, intracranial pressure and venous pressures have all been implicated as potentially contributory ¹³

skeletal anomalies in ~35% (range 23-45%) 2,3:

Unlike Chiari II, III, and IV malformations, Chiari I malformations often remain asymptomatic until adulthood, if it ever becomes symptomatic.

If symptoms are present, they may include a headache and those associated with brainstem compression, syringomyelia, or scoliosis. Headaches are typically located posteriorly and often associated with suboccipital neck pain. Coughing and straining can make the pain worse ¹⁵. There are also less defined symptoms which include imbalance, dizziness, cognitive impairment and fatigue ¹⁵, which if isolated can be at times difficult to ascribe to tonsillar ectopia, particularly if no other features of CSF flow obstruction is present.

The likelihood of becoming symptomatic is proportional to the degree of descent of the tonsils. In one study, all patients with >12 mm of descent were symptomatic, whereas approximately 30% of those with 5-10 mm descent remained asymptomatic ² (see MRI section for measurement technique).

The Chiari I malformation is characterized by an inferior position of the cerebellar tonsils relative to the foramen magnum ¹⁶. This is believed to be due to a mismatch between the size and content of the posterior fossa.

Four groups of Chiari I patients can be distinguished, according to different pathogeneses ⁹:

1. abnormal skull base (e.g. short clivus)

2. cervical segmentation anomalies (e.g. Klippel-Feil syndrome)

3. small cranial vault and/or posterior fossa and consequent overcrowding

4. excessive brain tissue (sometimes referred to as "acquired Chiari malformation")

Chiari I malformations need to be distinguished from low-lying tonsils (benign tonsillar ectopia) which is an asymptomatic and incidental finding in normal individuals, whereby the tonsils protrude through the foramen magnum by no more than 3-5 mm 1,2. The terminology of caudally displaced tonsils is discussed in the article on cerebellar tonsillar ectopia.

Although historically visible on myelography, cross-sectional imaging (especially MRI) is needed to diagnose accurately and assess for Chiari I malformations. In either case, the diagnosis is made by measuring the cerebellar tonsillar position (TP).

With modern volumetric scanning and high-quality sagittal reformats relatively good views of the foramen magnum and tonsils can be achieved although the intrinsic lack of contrast (compared to MRI) makes accurate assessment difficult. More frequently the diagnosis is suspected on axial images where the medulla is embraced by the tonsils and little if any CSF is present. This is referred to as a crowded foramen magnum.

MRI is the imaging modality of choice. On sagittal imaging, the best plane for assessing for the presence of Chiari I malformations, the tonsils are pointed, rather than rounded and referred to as peg-like. The sulci are vertically oriented, forming so-called sergeant stripes. Axial images through the foramen show crowding of the medulla by the tonsils.

The degree of tonsillar descent is determined by first drawing a line from the basion to the opisthion (anterior margin to the posterior margin of the foramen magnum); this defines the plane of the foramen magnum.

A measurement is then drawn perpendicular to this plan between it and the tip of the cerebellar tonsils, either in the midsagittal image or an adjacent parasagittal image, wherever the tonsils are most low lying 10,11.

See cerebellar tonsillar position article for more details.

Spinal cord MRI should be recommended as a syrinx may be seen if progressively enlarging or associated with symptoms may be an indication for surgical intervention ⁵.

CSF flow studies may also be useful to assess the flow surrounding the cervicomedullary junction.

Importantly, features of intracranial hypertension and craniospinal hypotension should be sought to ensure that cerebellar tonsillar ectopia is not secondary to abnormal intracranial pressure (and therefore not a true Chiari I malformation) 7,8.

Treatment is a surgical posterior fossa decompression and is usually reserved for symptomatic patients (e.g. strain or cough related headaches) or those with a syrinx.

How the posterior fossa decompression is carried out varies but can include a combination of the following: by removing part of the occipital bone and posterior arch of C1, performing a duroplasty, dividing arachnoid adhesions and bands, opening the forth ventricle and resecting part of the tonsils ¹⁵.

Successful decompression not only results in symptomatic relief but reduces tonsillar ectopia, reduces the size of the syrinx and restores CSF flow around the cervicomedullary junction ¹⁵.

It was first described in 1891 by Hans Chiari (1851-1916), an Austrian pathologist, based on the autopsies of children.

Imaging differential considerations include:

Distinguishing Chiari I malformation for pseudotumor cerebri is particularly important as treatment with a posterior fossa decompression can result in poor outcomes ⁵. Examination for features of intracranial hypertension is therefore crucial.

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Chiari I malformation | Radiology Reference Article | Radiopaedia.org

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Chiari I (Chiari 1) malformation is the most common variant of the Chiari malformations and is characterized by a caudal descent of the cerebellar tonsils through the foramen magnum. Symptoms are generally proportional to the degree of descent. M...

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Current research on Chiari Malformation: Present Day: Ongoing studies explore the genetic causes, improving surgical techniques and long-term patient outcomes.

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Current research on Chiari Malformation: Present Day: Ongoing studies explore the genetic causes, improving surgical techniques and long-term patient outcomes.

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Modern neuroscience is uncovering new information about Chiari Malformation's genetic origins, refining minimally invasive techniques and developing better symptom management strategies. Research in cerebrospinal fluid (CSF) dynamics, MRIs and post-surgery recovery is improving patients quality of life and helping future researchers make discoveries.

There is one specific expert in the field of Chiari Malformation that I have in mind...

Sources: https://www.americanbrainfoundation.org/diseases/chiari-malformation/#:~:text=Chiari%20Malformation%20Research%20Efforts,%2Dhindbrain%20(MHB)%20boundary.

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Chiari Malformation | American Brain Foundation

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Chiari malformations occur when part of the brainstem extends beyond the opening where the spinal cord connects to the skull. Learn about symptoms, diagnosis, and treatment options for CMs.

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Dr. John Oro: Present Day: A neurosurgeon specializing in Chiari Malformation, known for advancing surgical treatments and advocacy for patients.

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Dr. John Oro: Present Day: A neurosurgeon specializing in Chiari Malformation, known for advancing surgical treatments and advocacy for patients.

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Dr. John Oro is a renowned neurosurgeon specializing in Chair Malformation and other similar disorders. His contribution to refining decompression surgery and advocating for better patient care have made him an important person in the field of neuroscience. His expertise provides a lot of information about Chiari Malformation's history, treatment, and future directions.

From early anatomical descriptions to new and evolved research, the study of Chiari Malformation has been advanced a lot over 2 centuries. Pioneers like Hans Chiari, Julius Arnold, and Dr. John Oro have helped us understand more about this disorder and how we can improve diagnosis, treatment and patient outcomes.

Source: https://www.healthgrades.com/physician/dr-john-oro-2nd93

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Dr. John Oro, MD - Neurosurgeon in Denver, CO | Healthgrades

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Dr. John Oro, MD is a neurosurgeon in Denver, CO and has over 45 years of experience in the medical field. He graduated from University of Texas Medical Branch in 1978. He is affiliated with HCA HealthONE Aurora. He is accepting new patients and telehealth appointments.