Virtues and vagaries of high-resolution CT air cisternography in the diagnosis of acoustic neuromas.

A series of 125 consecutive, bilateral, high-resolution, computerized tomographic (CT) air cisternograms was prospectively reviewed and analyzed. Emphasis was placed on identifying problems encountered in performing the study and potential sources of error in interpretation. In two patients there was difficulty in transporting the air bolus because spinal cord tumors coexisted with bilateral acoustic neuromas. Potential false-positive results were avoided in four patients by persistent efforts to fill the internal auditory canal. Later reexaminations were recommended for four patients whose examinations were suspicious or suggestive of tiny acoustic neuromas. Unilateral Mondini malformation was incidentally diagnosed in one patient. Six patients required therapy for persistent headache after lumbar puncture. High-resolution CT air cisternography is believed to be the method of choice for investigating the nonenhancing or small acoustic neuroma. However, this method is not without potential problems, some of which are discussed.