Chiari Malformations Video

Contents

• Chiari Malformation Video
• What are Chiari Malformations?
• What is Chiari 1 Malformation?
• Whats is  Chiari 2 Malformation?
• Whats is  Chiari 3 Malformation?
• What is Chiari 4 Malformation?
• What is Chiari Type 0 and Chiari Type 1.5 ?

What are Chiari Malformations?

• Chiari Malformations are a group of abnormalities which involve the rhombencephalon which is also called as Hind brain and the contents of the CV junction.
• We have 6 types of Chiari malformations

What is Chiari 1 Malformation?

• In the MRI below, the foramen magnum has two points, the Basion and the opisthion. A line joining these points is called McRae's line. The herniation of tonsils and other brain structures is measured from this line.
• 5-mm or more caudal displacement of the cerebellar tonsils inferior to the foramen magnum
• This herniation and compression restricts normal CSF flow across the craniocervical junction
• Commonly associated findings are cervical syringomyelia(50-75%) and, on occasion, hydrocephalus (10%)

What is Chiari 2 Malformation?

• In Chiari 2 Malformation there is a greater amount of tissue that extends into the spinal canal compared to the chiari 1 malformation 
• There is  characteristic displacement of the medulla, fourth ventricle, and cerebellum through the foramen magnum. 
• almost all neonatal patients with Chari II have a  myelomeningocele
• Can have tectal beaking

What is Chiari 3 Malformation?

• Extremely rare 
• Characterized by low occipital and high cervical encephalocele
• There is herniation of posterior fossa contents, that is, the cerebellum and/or the brainstem, occipital lobe, and fourth ventricle. 

What is Chiari 4 Malformation?

• This is characterized by marked cerebellar hypoplasia or aplasia and tentorial hypoplasia. 
• There is no hindbrain herniation.
• No hydrocephalus

What is Chiari type 0 and Chiari Type 1.5 ?

Chiari type 0

• syringohydromyelia without hindbrain herniation that respond to posterior fossa decompression  (CSF flow across foramen magnum impaired)

Chiari type 1.5

• Severe form of Chiari 
• Entire cervicomedullary junction (and obex) is situated below the foramen magnum 

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CLASSIFICATION OF ARNOLD CHIARI MALFORMATIONS

https://www.worldsurgeryforum.net/2019/12/classification-of-arnold-chiari.html

ARNOLD CHIARI MALFORMATION RADIOLOGY AND BASIC CONCEPTS

https://www.worldsurgeryforum.net/2020/05/arnold-chiari-malformation-radiology.html

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What are Arnold Chiari Malformations?

• These comprise a group of abnormalities involving the rhombencephalon (hindbrain) and the contents of the CV junction 
• With common feature of impaired CSF circulation through the foramen magnum  
• May be Congenital or Acquired
• Ranging from simple herniation of the cerebellar tonsils through the foramen magnum to complete agenesis of the cerebellum 
• Presently there is no consensus regarding the precise definition, classification, etiology and the surgical management 
• Five types 
• No anatomical or embryological correlation between them 

Historical Background of Arnold Chiari Malformations

• 1883, John Cleland (Professor of anatomy in Glasgow, Scotland) - described hindbrain hernia in a child with myelodysplasia.
• 1891 and 1896, Hans Chiari- (Professor of Pathology at German University, Prague, Czechoslovakia): analyzed data from >40 postmortem examinations of patients with hindbrain malformations
• Chiari malformations I, II and III were coined in the earlier work and Chiari malformation IV was added in 1896 publication. 
• 1894, Julius A. Arnold(Professor of Pathology at Heidelberg, Germany)- described a single myelodysplastic patient with associated hindbrain herniation.
• Schwalbe & Gerdig included Arnold name in the eponym & designated it ARNOLD –CHIARI malformation 

What are the types of Chiari Malformations?

Chiari type 0 malformation

• alteration in Cerebro Spinal Fluid (CSF) hydrodynamics at the level of the foramen magnum. 
• they have syringomyelia either without tonsil herniation or with only mild tonsil herniation

Chiari Type I malformation

• caudal herniation of the cerebellar tonsils more than 5 mm below the foramen magnum
• typically associated with hydrosyringomyelia.
• not usually accompanied by descent of the brain stem or IV ventricle, nor associated with the presence of hydrocephalus.
• Most common type
• Presents in young 

Chiari type II malformation

• caudal herniation of the cerebellar vermis, brain stem, and IV ventricle through the foramen magnum. 
• associated with myelomeningocele, hydrocephalus, and, less frequently, hydrosyringomyelia. 
• hypoplastic tentorium cerebelli, cranial lacunae, anomalies of the Sylvius aqueduct may exist.

Chiari type III malformation

• consists of occipital encephalocoele, with some of the intracranial defects associated with Chiari II malformation.

Chiari type IV malformation

• cerebellar aplasia or hypoplasia, associated with aplasia of the tentorium cerebelli.

Images showing various Chiari malformations

Image of a Type 1 Arnold-Chiari Malformation. The cerebellum has descended 7mm and there are herniated cerebellar tonsils into the foramen magnum.

Artist's representation of a Chiari II malformation showing the points of potential obstruction that yield different subtypes of hydrocephalus

Neonate with Chiari malformation type III.T2-weighted mid-sagittal MRI scan of the patient shows a small posterior fossa, an deep parieooccipitalis fissure (open arrow), ad a partial callosal agenesis (curved arrow), and a caudal herniation of part of the brain stem through the foramen magnum, with inferior tip appearing between C5 and C6 (closed arrow). (https://www.sciencedirect.com/science/article/pii/S1930043315302697)

T1 weighted sagittal MRI showing a so called “Chiari IV” or primary cerebellar agenesis. There is a tiny portion of residual quadrangular lobule just caudal to the tectum and a normal sized posterior fossa. No associated meningomyelocele is present.

References

• Greenberg Handbook of Neurosurgery
• Fernández AA, Guerrero AI, Martínez MI, et al. Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification, diagnosis and treatment). BMC Musculoskelet Disord. 2009;10 Suppl 1(Suppl 1):S1. Published 2009 Dec 17. doi:10.1186/1471-2474-10-S1-S1 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796052/
• Hidalgo JA, Varacallo M. Arnold Chiari Malformation. [Updated 2019 Nov 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK431076/
• https://commons.wikimedia.org/wiki/File:MRI_of_human_brain_with_type-1_Arnold-Chiari_malformation_and_herniated_cerebellum_es.jpg
• https://commons.wikimedia.org/wiki/File:Chiari2.jpg
• Chiari malformation type III: Case report and review of the literature. Christina Andica, Ristaniah D. Soetikno. Radiology Case Reports, 8, 3, 2013 https://doi.org/10.2484/rcr.v8i3.831
• The Chiari malformations. Donald M. Hadley. Neurology in Practice, 72, 2, 2002 http://dx.doi.org/10.1136/jnnp.72.suppl_2.ii38

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https://www.worldsurgeryforum.net/2019/12/classification-of-arnold-chiari.html

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https://www.worldsurgeryforum.net/2020/05/arnold-chiari-malformation-radiology.html

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