動眼神経上枝に発生した眼窩内神経鞘腫の1例

Orbital Schwannoma Developing from the Superior Branch of the Oculomotor Nerve - Case Report

Ⅰ．は じ め に

　眼窩内神経鞘腫は眼窩腫瘍の1～6％^{2,8-10,14,15)}である．発生母地となった神経が同定できた症例は限られており，多くは発生部位が明確に特定されずorbital neurinoma^4,8)として報告されている．その理由として眼窩内は，その狭い空間に脂肪組織，筋，血管，結合組織とともに多数の神経が混在していること⁷⁾，術前に明らかな神経脱落症状を伴わないことなどが挙げられる⁸⁾．今回，眼窩内神経鞘腫の1例を経験し，術中に動眼神経上枝が発生母地であることを同定でき，術後に神経脱落症状を呈することなく摘出できたので，若干の文献的考察を加えて報告する．

Orbital schwannoma accounts for 1-6% of all orbital tumors and it is not easy to identify the origin of the tumor because of the anatomy of the orbit. A case of orbital schwannoma developing from the superior branch of the oculomotor nerve is reported. A 74-year-old female was admitted to our hospital with the chief complaint of left exophthalmus. MR imaging revealed a space-occupying lesion in the left orbit. Operation was performed through the transcranial approach. It was noticed that the tumor was developing from the nerve that runs into the superior rectus muscle or the levator palpebrae superioris muscle,and it was diagnosed as a schwannoma on frozen section histology during surgery. The tumor was successfully removed and,postoperatively,no additional defects occurred. Careful consideration of microsurgical anatomy is essential for surgery of orbital schwannoma especially when it's necessary to cut the nerves.