[Studies concerning the pathogenesis of trigeminal neuralgia caused by cerebellopontine angle tumors].

It has been well recognized that neurovascular compression can elicit trigeminal neuralgia (TN) and microvascular decompression surgery has become popular as a radical treatment of this clinical symptom. Cerebellopontine (C-P) angle tumors, however, as well known, can also cause TN. Four hundred fifty six patients with TN underwent posterior fossa exploration between 1984 and 1992 in our clinic, and among them, 45 (9.9%) patients harbored C-P angle tumors which were causative of TN. They included 22 epidermoids, 18 meningiomas and 5 neurinomas. The patient population consisted of 35 women and 10 men, ranging in age from 28 to 73 years, with a mean age of 51.7 years. The mean age of the patients of TN with tumors is considerably lower than that of neurovascular compression patients (61.0 years), particularly in cases of neurinomas (44.4 years) and epidermoids (48.0 years) (p < 0.01). Such difference in ages at the onset of symptom may be explained by the fact that the tumor growth in the C-P angle develops earlier than changes of the vasculature of the vertebrobasilar artery system by aging. Anatomical relationships between the 5th cranial nerve and offending arteries or tumors verified at surgery are as follows; Type A: The nerve is totally encased by the tumor. Type B: The axis of the nerve is distorted by the tumor. Type C: The nerve is shifted by the tumor and is compressed by the artery contralaterally. Type D: The nerve is compressed by the artery which was displaced by the tumor.(ABSTRACT TRUNCATED AT 250 WORDS)