一次性動眼神経麻痺をきたした軽症頭部外傷の2症例

Primary Oculomotor Nerve Palsy due to Mild Head Injury―Report of Two Cases

はじめに

　われわれの日常臨床において頭部外傷に伴い動眼神経麻痺をきたした症例を多くみるが，その多くは二次性動眼神経麻痺といわれる重症頭部外傷における脳ヘルニアに伴うものである。しかし頭部外傷において，それ以外の原因によるいわゆる一次性動眼神経麻痺をきたす頻度は頭部外傷患者で1％前後と報告されている。今回，上記のように比較的稀な一次性動眼神経麻痺をきたした軽症頭部外傷の2症例を経験したので，文献的に発生機序を個別に考察したので報告する。

Abstract

　Two patients with primary oculomotor nerve palsy due to direct mild head injury are reported.　They presented with internal ophthalmoplegia, dilated nonreactive pupils, and very mild disturbance in consciousness.　Except for the persistent oculomotor nerve palsy, both the patients recovered fully within one week.　Neither demonstrated a history that was suggestive of a cause for their oculomotor nerve palsy.　Initial CT scans demonstrated localized subarachnoid hemorrhage around the brain stem.　One of the patients had sustained a fracture of the anterior clinoid process.　As the underlying pathophysiologic mechanism underlying the oculomotor nerve palsy we suspected mild injury to the pupillomotor fibers at the anterior petroclinoidal ligament and that of the pupillary fibers at the posterior petroclinoidal ligament.　We speculate that these perforating fibers at the anterior petroclinoidal liqament acted as a fulcrum due to downward displacement of the brainstem at the time of impact.

(Received: April 5, 2007, Accepted: September 10, 2007)