Partial fascicular oculomotor paresisを呈した中脳梗塞の1例

A Case of Partial Fascicular Oculomotor Paresis Caused by Midbrain Infarction

要旨　片側の眼瞼下垂と上転障害のみで発症した中脳腹側の小梗塞，74歳男性例を報告した。神経学的には上眼瞼挙筋，上直筋および下斜筋の障害であることより，中脳レベルにおけるpupil-sparing型の動眼神経核下性線維（oculomotor fascicles）の損傷が示唆された。入院時MRI水平断では中脳腹側に虚血巣が確認され，またT2強調冠状断においては赤核直下に責任病巣が同定された。これは，動眼神経核から外尾側へ広がる核下性動眼神経線維の下方成分の走行部位に一致する所見と思われた。以上より，本症例は現在まで推測されている動眼神経核から外尾側へ散開する上眼瞼挙筋，上直筋および下斜筋への核下性線維の損傷に基づくpartial fascicular oculomotor palsyと考えられ，神経学的所見と画像所見の一致をみた貴重な症例と思われた。

We report a 74-year-old man with an ischemic lesion in the ventral midbrain. He presented with contralateral ptosis and marked upward gaze paresis of the right eye. Neurological examination revealed partial oculomotor nerve palsy caused by impairment of the right levator palpebrae, superior rectus and inferior oblique muscles. This finding is highly suggestive of a possible lesion in the midbrain affecting the oculomotor fascicular fibers. Magnetic resonance images showed an ischemic lesion in the paramedian area of the right midbrain tegmentum. The coronal view of T2-weighted imaging clearly demonstrated to be the site of lesions below the red nucleus. It seemed to be coincidental with the impaired site of involving the caudal part of oculomotor fascicular fibers emerging from the nucleus. This report is considered to be a typical case of partial fascicular oculomotor paresis based on impairment of the caudal part of oculomotor fascicles for the levator palpebrae, superior rectus, and inferior oblique muscles. This is a valuable case to be documented in which neurological site of lesions are consistent with those found in radiological study.