Developmental anomalies affecting the fourth ventricular outflow region: a report of four cases.

Developmental anomalies affecting the hind brain, cerebellum and spinal cord with associated malformations of the skull base and cervical spine, show a wide degree of variability and overlap so that cases are often difficult to classify into a fixed category such as the Arnold-Chiari malformation Type 1 or Type 2, or the Dandy-Walker syndrome. The 4 cases presented here illustrate this problem and offer support for the hypothesis that these conditions may be merely the varying expression of a common pathological process. The CT brain scan may prove to be a valuable means of allowing early recognition of these anomalies so that effective surgical treatment can be given at an early stage in their natural history, possibly thereby preventing the progression or development of central cord cavitation with its significant and permanent disabilities.