[Clinical study in vertiginuous patients suspected of having neurovascular compression syndrome of the eighth cranial nerve].

Neurovascular compression syndrome of the 5th and 7th cranial nerves has been recognized as the cause of trigeminal neuralgia and hemifacial spasm. On the other hand, it is still difficult to diagnose vertigo as neurovascular compression syndrome of the 8th cranial nerve. To detect some specific finding in this syndrome of the 8th cranial nerve, 5 patients with vertigo with hemifacial spasm were examined for the clinical course and neuro-otological features. In all patients MRI and/or angiography suggested vascular compression against the 8th cranial nerve. The clinical courses of these patients revealed various symptoms resembling benign paroxysmal positional vertigo, vestibular neuronitis and Meniere's disease. Audiograms showed two normal hearing patterns, bilateral high frequency hearing loss probably due to aging in one case, bilateral C5-dip in one and fluctuating unilateral hearing loss like Meniere's disease in one. The prolongation of IPL I-III on auditory brainstem response proposed as a criterion by Møller was detected in one case. No response in the caloric test was found in two cases. These abnormalities in the auditory brainstem response and caloric test appeared to be useful for diagnosis but were uncommon findings in all cases. Electronystagmographic examinations including the eye tracking test, optokinetic nystagmus and optokinetic pattern were all normal. We could not find any specific clinical findings valuable for diagnosis of neurovascular compression syndrome of the 8th cranial nerve. It is proposed that the indication of microvascular decompression should be decided carefully.