Roentgenographic Diagnosis of Acoustic Nerve Tumor

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THE diagnosis of acoustic nerve tumor is based primarily upon the results of clinical examination; roentgenographic examination serves as a secondary diagnostic aid. This lesion is not uncommon, constituting approximately 9 per cent of all brain tumors.

The tumor is found attached to the eighth cranial nerve and lies in the angle between the cerebellum and the brain stem. The direction of growth is variable; a tumor may grow quite large without appreciably involving the petrous apex or extending into the acustic meatus. By contrast, it may weigh only a few grams with most of its mass within the meatus, causing marked erosion. Although initially it was postulated that the tumor arose solely from the vestibular branch,1 now it is known that either the vestibular or the cochlear branch of the eighth nerve may be the site of origin.2 Acoustic nerve tumors have been reported in the literature to be of two basic histologic types.3 Most of them are considered to be neurinomas (neurilemoma, perineural fibroblastoma); in these, the nerve fibers are confined to the capsule of the tumor mass with no fibers present within the lesion. A small percentage are neurofibromas with nerve fibrils coursing through the tumor. The latter are reported as occurring with von Recklinghausen’s disease;4 they tend to be bilateral and familial,5 and may be associated with a meningioma.6, 7 All of the acoustic tumors in this series were reported as neurilemomas or neurinomas, including two cases with von Recklinghausen’s neurofibromatosis peripherally. It seems definite that . . .



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