Ectopic choroid plexus within a juvenile arachnoid cyst of the cerebellopontine angle: cause of cyst formation or reason of cyst growth.

The unusual and rare case of a 6-year-old boy is reported who presented with an arachnoid cyst located in the cerebellopontine angle incorporating an ectopic piece of choroid plexus tissue. A microneurosurgical cyst wall resection was performed and the plexus tissue identified and removed. The rare occurrence of ectopic choroid plexus tissue within cysts of the CNS is discussed. Copyright 2000 S. Karger AG, Basel