Computed tomography with gas cisternography for detection of small acoustic tumors. A study of five false-positive results.

Cranial computed tomography (CT) with gas cisternography is reported to be the most accurate method of detection of small acoustic tumors. However, five false-positive CT results experienced in three years are now reported. This is a false-positive rate of 22% for tumors with less than 5-mm protrusion into the cerebellopontine angle, and a false-positive rate of 50% for tumors with less than 2-mm protrusion. A false-positive result is suspected if no mass protrudes at the porus or if gas enters the lateral internal auditory canal.