MR diagnosis of acoustic neuromas.

Two hundred forty-three patients with clinically suspected acoustic neuroma were evaluated radiologically by CT, and in selected cases CT cisternography and/or magnetic resonance imaging. Fifty-one acoustic neuromas were diagnosed and surgically removed; 36 were large tumors with extracanalicular extension and 15 were strictly intracanalicular small tumors. With routine CT (without and with contrast medium) large and enhancing lesions (36 of 51) were visualized, but small intracanalicular tumors (15 lesions) were missed. The latter were visualized by CT cisternography (seven cases) or MR (eight cases). Magnetic resonance, when used with spin-echo technique using both short as well as long sequences for axial and coronal thin slices (5 mm or smaller), demonstrated all the surgically verified lesions.