ASSOCIATION OF HETEROTOPIC NEUROGLIAL TISSUE WITH AN ARACHNOID CYST IN THE INTERNAL AUDITORY-CANAL

An arachnoid cyst arising within the internal auditory canal, or withi n the cerebello-pontine angle and subsequently extending into the inte rnal meatus and enlarging it, is a rare occurrence. Nevertheless, the neurootologist and the neurosurgeon have an interest in its existence because its clinical manifestations are identical with the ones produc ed by a schwannoma, involving overwhelmingly the cochleovestibular ner ve in that region. An equally rare observation in that location is the presence of ectopic neuroglial tissue. The two can occur independentl y or in combination. Examples of such lesions are presented, and the p ossible pathogenesis is discussed.