Chiari malformation

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Basic details about Arnold Chiari malformation

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Arnold-Chiari malformation :

Arnold-Chiari malformation Dr. Pratheep. Joseph. Kottam DM Neuro, Assistant Professor in Neurology, MOSC Medical College, Kolenchery, Kerala, India .

Arnold-Chiari Malformation:

Arnold-Chiari Malformation Congenital malformations at the base of the brain Cerebellar tonsil ± medulla prolapsing into spinal canal Classified as Neural dysraphism / NTD /Hindbrain malformations 4 types Any type may be a/w – hydrocephalus, Syrinx

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McGregor's line McRae's line Chamberlain's line

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McRae's line extends from anterior lip of foramen magnum to posterior lip of foramen magnum Chamberlain's line - from roof of hard palate to posterior lip of foramen magnum McGregor's line extends from roof of hard palate to most caudal portion of occipital bone

Chiari I :

Chiari I MC type Extension of cerebellar tonsils below foramen magnum No Meningomyelocele Slight extension of tonsils below foramen is normal – 5 mm Often asymptomatic

Chiari I - Clinical manifestations :

Chiari I - Clinical manifestations Onset - young adulthood a/c onset of symptoms may occur after prolonged neck extension Headaches, visual disturbances Inc ICT – occipital head ache Neuro-otological complaints Cranial nerve dysfunction - Lower cranial nerves can be involved

Chiari I - Clinical manifestations…:

Chiari I - Clinical manifestations… Downbeat nystagmus Cervical Syrinx Progressive Cerebellar ataxia Sleep apnea Myelopathy - Progressive Spastic quadriparesis

Caudal descent of nucleus gracilis (curved arrow) marking obex. Tonsils (arrow) protrude through foramen magnum & cisterna magna is obliterated.:

Caudal descent of nucleus gracilis (curved arrow) marking obex. Tonsils (arrow) protrude through foramen magnum & cisterna magna is obliterated.

Tonsils (curved arrow) protruding through foramen magnum posteriorly compressing upper cervical cord. +mild ventriculomegaly (arrow).:

Tonsils (curved arrow) protruding through foramen magnum posteriorly compressing upper cervical cord. +mild ventriculomegaly (arrow).

Treatment for symptomatic patients :

Treatment for symptomatic patients Cranio-cervical decompression - decompress cerebellum, spinal cord, brainstem This improves CSF flow through foramen magnum Often leads to improvement in Syringomyelia

Chiari 1.5 :

Chiari 1.5 Type I + Medulla descends below foramen magnum Brainstem dysfunction is more likely to occur

Chiari II malformation:

Chiari II malformation Cerebellar vermis & caudal brainstem descend + an associated myelomeningocele Infantile onset Hydrocephalus and Syringomyelia are common Cerebellar signs Associated anomalies - small posterior fossa, kink in the medulla and polygyria

Chiari II malformation…:

Chiari II malformation… Lower cranial nerve palsy B/L Abducens palsy Facial weakness Deafness Strider Sternomastoid paralysis Tongue fasciculation

Small PF, large massa intermedia, beaked tectum, callosal dysgenesis, elongated 4th V & herniating nodulus, choroid plexus & medullary spur (arrows):

Small PF, large massa intermedia, beaked tectum, callosal dysgenesis, elongated 4th V & herniating nodulus, choroid plexus & medullary spur (arrows)

Beaked tectum (arrow), large massa intermedia (curved arrow), dysgenetic corpus callosum, small 4th ventricle, and protrusion of tissue through foramen magnum.:

Beaked tectum (arrow), large massa intermedia (curved arrow), dysgenetic corpus callosum, small 4th ventricle, and protrusion of tissue through foramen magnum.

Chiari II:

Chiari II Elongated 4th V - open arrow Tissue cascade - vermis, choroid plexus - curved arrow Medullary spur – white arrow Kink - black arrow

Chiari II with callosal dysgenesis. High-riding 3rd V, small posterior fossa contents :

Chiari II with callosal dysgenesis. High-riding 3rd V, small posterior fossa contents

Chiari III:

Chiari III Cerebellum & brainstem extends into an infra tentorial Encephalocele Cervical spina bifida

Occipital encephalocele, beaked tectum (arrow) and large massa intermedia.:

Occipital encephalocele, beaked tectum (arrow) and large massa intermedia.

Treatment:

Treatment Cerebrospinal fluid diversion Diversion pre-resection sac may allow decreased tension on brain stem Resect or repair sac

Chiari IV:

Chiari IV Cerebellar & brainstem hypoplasia rather than displacement - variant of Dandy-Walker

Causes of hydrocephalus:

Causes of hydrocephalus Narrow aqueduct due to elongated Pons & Medulla Occlusion of FM due to displaced medulla & cerebellum Cerebellum obliterates cisterna magna Foramen of Lushka & Magendie open in to cervical spinal canal Arachnoids around brainstem & cerebellum is fibrotic

Associated malformations:

Associated malformations Polymicrogyria Low filum terminale – down to sacrum Small posterior fosse Cervical spina bifida Basilar impression Occipitalisation of atlas

Findings s/o disease at foramen magnum:

Findings s/o disease at foramen magnum Down-beat nystagmus Combination of long tract signs + LMN dysfunction in lower cervical spinal cord LMN dysfunction is due to impaired spinal venous drainage at foramen magnum

Investigations:

Investigations Sagittal MRI scans of brain and cervical spine CSF flow at foramen magnum can be evaluated using phase-contrast MRI & cardiac gating to acquire images throughout cardiac cycle Low tonsils with normal rounded shape are usually asymptomatic

Theories of origin:

Theories of origin Traction theory – tethered cords & traction Pulsion theory – fetal hydrocephalus Crowding theory – Small posterior fosse Ectopic expression of a segmentation gene in rhombomeres

Rx :

Rx Non progressive – no Rx Progressive - Cervical laminectomy + foramen magnum enlargement + treatment of Syrinx Repair of myelomeningocele and shunting of hydrocephalus

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