視索に形態的変化を確認できた視索症候群の1症例

Morphological changes of the optic tract in a case of optic tract syndrome

要約　背景：視索症候群は片側の視索の機能障害によるが，視索に形態的変化があるか否かは知られていない。目的：磁気共鳴画像（MRI）で片側の視索に異常があった1症例の報告。症例：19歳女性が他医で緑内障と診断され，その6か月後に精査を希望して受診した。小児てんかんがあり，4年間の投薬既往がある。所見：矯正視力は左右とも1.2で，眼圧は右11mmHg，左12mmHgであった。両眼の視神経乳頭耳側に蒼白化があり，右側の非調和性同名半盲があった。光干渉断層計で，右眼に横方向の乳頭周囲神経線維層厚の減少と中心窩鼻側の神経節細胞複合体の菲薄化，左眼に縦方向の乳頭周囲神経線維層厚の減少と中心窩耳側の神経節細胞複合体の菲薄化があった。MRIで左側視索の縮小と容積減少があり，左側の視索症候群と診断した。結論：本症例は，新知見として視索の機能障害と形態的変化を示す，視索症候群であった。

Abstract.　Purpose：To report a case of optic tract syndrome who showed unilateral changes in the optic tract by magnetic resonance imaging（MRI）. Case：A 19-year-old female had been diagnosed with glaucoma elsewhere 6 months before. She visited us asking for second opinion. She had received medication for 4 years because of childhood epilepsy. Findings： Corrected visual acuity was 1.2 in either eye. Intraocular pressure was 11 mmHg right and 12 mmHg left. Both eyes showed temporal pallor of the optic disc and right-sided incongruous homonymous hemianopia. The right eye showed, by optical coherence tomography, decreased thickness of circumpapillary retinal nerve fiber in the horizontal direction and decrease in ganglion cell complex nasal to the fovea. The left eye showed decreased thickness of circumpapillary retinal nerve fiber in the vertical direction and decrease in ganglion cell complex temporal to the fovea. MRI showed reduction in size and volume of left-side optic tract, leading to the diagnosis of optic tract syndrome. Conclusion：The present case of optical tract syndrome showed functional and morphological changes of the optic tract. To our best knowledge, this finding has not been reported before.