The Diagnosis of Small Acoustic Neuromas by Air CT Cisternography and Canalography
Routine contrast-enhanced CT scans generally cannot exclude the presence of an acoustic neuroma of 1 cm. or less in size (1,2,3). CT — metrizamide cisternography, though excellent in defining a cisternal mass lesion, cannot be visualized intracanalicular unless the acoustic canal is grossly enlarged and therefore cannot exclude the presence of a lesion limited to canal or porus (2). Pantopaque cisternography has so far been the only neuroradiologie examination that can exclude an intracanalicular acoustic neuroma, although the study may be falsely positive in a small percentage of cases (4, 5, 6) and has a potential risk of producing adhesive arachnoiditis (7,8). The presence of pantopaque may also preclude the CT evaluation of the CP angle cistern at a future date.
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