False positive roentgenologic diagnosis of small intracanalicular acoustic neurinomas

1. Two false positive contrast studies are presented. The first was due to either inflamed vestibular nerves or incomplete filling to the internal canal. The second was due to arachnoiditis and adhesions between the dura and seventh and eighth cranial nerves.2. The technique of using a small amount of pantopaque (1 cc.) combined with polytomography is described and discussed briefly.3. The procedure of inner ear fluid tap (diagnostic labyrinthotomy) is a reliable procedure for detection of a small intracanalicular tumor. Therefore, it should be performed when the contrast study is equivocal or unsatisfactory, or there is a question of whether or not the filling defect represents an intracanalicular tumor. It is important especially in those patients who present with a progressive unilateral sensorineural loss with normal tomographic findings of the internal auditory canals, and those who are allergic to contrast media.