Anatomic variants of the cerebello-pontine cisterns and their significance in positive contrast cisternography.

Far lateral extension of the cerebello-pontine cistern is a common variant which is found in greater than 50% of people. When present it may cause the internal auditory canal to be obscured during positive contrast cisternography. A technique of cisternography is described which facilitates the diagnosis of intracanalicular lesions as well as better delineating small lesions in the cerebello-pontine angle.