Computerized axial tomography with air contrast of the cerebellopontine angle and internal auditory canal

The introduction of computerized axial tomography (C.T.) in 1973 completely changed the diagnostic evaluation of acoustic neuromas. Seventy to eighty percent of all acoustic neuromas can be diagnosed with intravenous enhanced C.T. scan. Acoustic tumors with a diameter of less than 1.5 cm, however, are not consistently seen on C.T. scan. Twenty-six consecutive patients were evaluated by C.T. scan with air contrast posterior fossa myelography (C.T. air cisternography). Nineteen studies were normal, with complete air filling of the internal auditory canal. Surgically verified acoustic neuromas were demonstrated in four patients. Two studies were inconclusive and there was one false positive. Other than headaches, there is no morbidity associated with this technique. C.T. air cisternography should be considered as the definitive study for evaluating patients for acoustic neuromas who have normal intravenous contrast enhanced C.T. scans. This study reports the first intracanalicular tumor diagnosed with this technique.