Definition: caudal displacement of the cerebellum with/without the medulla oblongata, through the foramen magnum, due to CVJ anomalies
Type I CM (Chiari I malformation)
- Usually symptomatic in adolescence/young adulthood:
- Occipital headache (exacerbated by valsalva maneuvers and physical activity)
- Neck pain
- Radicular pain in the shoulders and arms
- Lower cranial nerve disorders
- Cerebellar symptoms (e.g., dysarthria, ataxia)
- Downbeat nystagmus
- Some patients develop syringomyelia and/or hydrocephalus.
Type II CM (Arnold-Chiari malformation)
- Usually symptomatic in infancy
- Obstructive hydrocephalus: Displacement of brain tissue into the foramen magnum results in stenosis of the cerebral aqueduct
- Breathing difficulties, including apneic episodes
- Feeding difficulties
- Muscle weakness or numbness
- Always associated with myelomeningocele: manifests with motor and/or sensory deficits at and below the level of the lesion
- Some patients develop syringomyelia