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q21 - raji_321
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01-24-2008, 08:07 AM
An infant is born with hydrocephalus. CT studies demonstrate herniation of the cerebellum into the spinal canal. This is an example of which of the following?
A. Arnold-Chiari malformation B. Dandy-Walker malformation C. Holoprosencephaly D. Lissencephaly E. Porencephaly
01-24-2008, 08:13 AM
The correct answer is A. Arnold-Chiari malformations are congenital herniations of hindbrain structures into the spinal canal. In type I Arnold-Chiari malformation, the cerebellar tonsils herniate into the foramen magnum; in type II, parts of the hindbrain, cerebellar vermis, and fourth ventricle herniate into the foramen. This second type is commonly associated with meningomyeloceles. Other neonatal presentations associated with Arnold-Chiari malformation include hydrocephalus (because of cerebrospinal fluid obstruction) and brainstem dysfunction (causing stridor and poor swallowing). Milder cases may present later in life with spinal cord or cerebellar symptoms.
Dandy-Walker malformation (choice B) is associated with hypoplasia of the cerebellum associated with an enlarged fourth ventricle. Holoprosencephaly (choice C) is a complex malformation of the brain such that only a single large monoventricular cerebral hemisphere exists. Lissencephaly (choice D), or agyria, means "smooth brain" and is a condition characterized by a lack of hemispheric sulci and severe neurologic impairment. Porencephaly (choice E) is a severe cleft in the brain that allows the ventricles to communicate with the subarachnoid space. |
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