The Arnold-Chiari malformation is a malformation of the brain in which part of the brainstem and cerebellum are herniated into the cervical vertebral canal through the foramen magnum.
Arnold-Chiari malformations are classified anatomically:
- Type I
- downward displacement of cerebellar tonsils only
- associated with syringomyelia in up to 80% of cases
- many patients are asymptomatic
- mean age of onset 25
- Type II
- downward displacement of cerebellum, lower pons and medulla
- commonest form
- tends to present in childhood
- associated with spina bifida and hydrocephalus
- more severe form
- Type III
- cerebellar herniation into a high cervical meningocele
- Type IV
- Hypoplasia/aplasia of the cerebella hemispheres
Clinical manifestions of Arnold-Chiari include:
- Downbeat nystagmus
- Headaches – made worse by valsalva manoeuvres
- Vertigo
- Tinnitus
- Dysarthria
- Dysphagia
- Parasthesias
- Facial pain
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