視索障害により同名半盲を呈したプロラクチン産生下垂体腺腫

Homonymous hemianopsia due to optic tract disorder with prolactin producing pituitary adenoma

要約　緒言：視索障害により同名半盲を呈したプロラクチン（PRL）産生下垂体腺腫を経験したので報告する。

症例：患者は79歳，男性。認知機能低下のために近医神経内科を受診し，頭部単純MRIで下垂体腺腫が疑われ，太田記念病院脳神経外科を紹介され受診した。その後，眼症状の精査依頼があり眼科に紹介となった。初診時矯正視力は右0.5，左0.7。右眼視神経乳頭の色調はやや蒼白であったが，対光反射に異常はなかった。左眼視神経乳頭には異常はなかったが，相対的瞳孔求心路障害が陽性だった。動的視野検査では左同名半盲を呈していた。光干渉断層計では，ganglion cell analysisで視野異常に一致した菲薄化を認めた。頭部造影MRIでトルコ鞍から鞍上部右側後方に不整形な造影効果を伴う腫瘤を認め，右海綿静脈洞浸潤があり，視交叉を巻き込み後方に進展しており，右基底核，前頭葉にかけて出血を伴う巨大囊胞を伴っていた。血中PRLが16,610.10ng/mlと高値を示し，PRL産生下垂体腺腫と診断しブロモクリプチン内服で治療開始となった。

結論：下垂体腺腫による視野異常は，視交叉を下方から圧迫し耳側半盲などの耳側視野欠損を呈することが多いが，その進展形式によって視索障害による同名半盲をきたすことがあると考えられた。

Abstract　Purpose：We report a case of prolactin-producing pituitary adenoma that presented as homonymous hemianopsia due to the optic tract disorder.

Case：A 79 year-old male with decreased cognitive function, in whom pituitary adenoma suspected in head MRI was referred to neurosurgery at our hospital. The best-corrected visual acuity was 0.5 in the right eye and 0.7 in the left eye. The color of the optic disc of the right eye was moderately pale, but the light reflex was normal. No abnormalities were seen in the optic disc of the left eye, but relative afferent pupillary defect was positive. Left homonymous hemianopsia was diagnosed. A thinning area was seen in ganglion cell analysis with optical coherence tomography according to the visual field defect. Head contrast-enhanced MRI showed an irregular mass with the cystography effect. It extended from the sella turcica to the right side of the suprasellar region and extended backward invading the right cavernous sinus, optic chiasm, it included a giant cyst with bleeding from the right basal ganglia to the frontal lobe. The prolactin（PRL）level in the blood was 16,610.10 ng/ml, and he was diagnosed with PRL-producing pituitary adenoma. He has been followed up with bromocriptine intake.

Discussion：Visual field abnormality due to the pituitary adenoma is often presented as a temporal visual field defect such as the temporal hemianopia. However, depending on the type of tumor extension, it may compress the optic tract and present as homonymous hemianopsia.