Arnold Chiari malformation is characterized by all except
Ans. is 'a' i.e., Hypoplasia of cerebellar vermis Arnold-chiari malformation* Arnold-Chiari malformation consists of herniation of the cerebellum and fourth ventricle into the foramen magnum, flattening of the base of the skull, and spina bifida with meningomyelocele.* Chiari malformation is divided intoi) Type I: Produce symptoms during adolescence or adulthood is usually not associated with hydrocephalus. The deformity consists of displacement of cerebellar tonsils into the cervical canal,ii) Type II: It is characterized by progressive hydrocephalus with a myelomeningocele in newborns. There is a failure of pontine flexure during embryogenensis, which results in elongation of 4th ventricle; kinking of brainstem and breaking of quadrigeminal plate (tectum); along with displacement of inferior vermis, pons and medulla into cervical canal. This causes widening of cervical canal (syringomyelia),iii) Type III: Usually associated with occipital encephalocele and causes abundant neurological deficit,iv) Type IV: Characterised by lack of cerebeller development and usually not compatible with life.