Intracanalicular neurilemmomas: clinicopathologic study.

Twenty-five patients with intracanalicular neurilemmonas were studied, the largest series yet reported. The tumors were most frequent in men by a ratio of 2:1, occurred more often on the left acoustic nerve, generally associated with long duration of symptoms and were equally distributed in the third to fifth decades, but the prevalence slightly increased in the sixth and seventh decades. A shorter length of illness occurred in younger persons as well as most patients with von Recklinghausen's disease. The length of illness ranged from six months to 35 years. Symptoms generally were limited to the auditory nerve except in three instances of involvement of the facial nerve. These three cases were the only ones with preoperative facial palsy. Posterior fossa myelogram was the most useful diagnostic acid. The rate of growth in one patient was estimated to be 1 to 2 mm per year by serial study of myelograms, but the growth rate is probably variable. CT scans were not useful in detecting small tumors. Histologically, most tumors less than 1 cm in diameter were primarily composed of Antoni type A tissue. Vascular malformations were found within the tumor in three cases. Altered blood vessels are the mechanism whereby characteristic changes occur in the cerebrospinal fluid (CSF). Small tumors generally lack blood vessels, hence are less often associated with abnormal CSF.