Filling defects and nonfilling of the internal auditory canal in posterior fossa myelography.

A review of posterior fossa myelography at St. Joseph Hospital within the past 5 years is presented. Three false positive diagnoses have been found. Two of the cases were proved to have arachnoiditis, while one demonstrated a knuckle of artery in the canal. One case with large acoustic neuromas causing nonfilling of the contralateral canal is presented. One case with Type I intracanalicular tumor out of 40 acoustic neuromas in the series was diagnosed prior to surgery. The indication for posterior fossa myelography are discussed with a review of the literature.