聴神経腫瘍の早期診断を目的とした顔面神経・三叉神経機能検査法

USEFUL TEST IN THE EARLY DIAGNOSIS OF ACOUSTIC NEUROMAS

緒言

　聴神経腫瘍の手術方法の進歩は近年特に目覚しく，顔面神経はもとより，聴力を保存した根治手術も可能となつてきた。

　聴神経腫瘍は病理組織学的検索の結果，多くの場合前庭神経の上・下枝いずれかの神経鞘より生ずることが明らかとなつている。従つて，内耳道内に限局あるいは小脳橋角部に僅かに突出した程度の小さな腫瘍の場合，直接侵襲を受けていない蝸牛神経を保存しながら，腫瘍を完全に摘出するすることも理論的には可能と思われる。

　House （1968）は，7年間に手術を行なつた一側聴神経腫瘍200例中，聴力を保持できたものが7例あったと報告している。

Acoustic neuroma usually arises within the inter-nal auditory canal. In the early stage while it stays there, it may become to press facial nerve. As it grows beyond the canal, it affects the fifth nerve, first of all.

We have attempted to get its early diagnosis and have tested, quantitatively, function of the facialnerve and the fifth nerve by two methods ; blink test and corneal reflex recording.

A) Blink Test : Blink reflexes of both eyes, eli-cited by light glabella-tap with percussion hammer, are recorded separately by means of penoscillography. Diphasic spiking is a typical pattern and its ampli-tude shows speed of response. In normal subjects amplitude of oscillographic tracings is almost equal in both eyes. Discrepancies in this response of both eyes. Discrepancies in this response of both eyes more than 5% are regarded as to be pathological. The blink test was positive in 11 of 12 patients who had tumors of the cerebellopontine angle, 7 of whichwere acoustic neuromas.

B) Corneal-reflex Recording : The threshold of corneal reflex in both eyes to air pressure are com-pared to each other. The corneal reflex is recorded by electroencephalography and air pressure is re-corded by strain gauge manometer. We point out the importance of a unilateral decrease in corneal sensitivity in the diagnosis of cerebellopontine angle lesions. This method was positive in 10 patients who had tumors of the cerebellopontine angle. Finding fifth nerve abnormality indicates a tumor which is most probably touching the brain stem.