弱視治療中に発見された視路視床下部毛様細胞性星細胞腫の1例

A case of optic hypothalamic pilocytic astrocytoma detected during amblyopia treatment in a child

要約　目的：小児の弱視治療中に発見された視路視床下部毛様細胞性星細胞腫について報告する。

症例：初診時，11か月の男児，軽度眼振にて大阪医科薬科大学病院に紹介され受診した。前眼部，中間透光体，眼底に異常なく，眼球運動も良好で，眼位は間欠性外斜視の状態であった。2歳9か月になり，左視力不良，遠視性不同視があり，左不同視弱視と診断して眼鏡処方による弱視治療を開始した。しかし，その後も視力の改善は得られず，眼位も間欠性外斜視から恒常性外斜視に移行した。この間，相対的瞳孔求心路障害は明らかでなく，眼球突出は認めていない。5歳時にMRIを施行したところ，左視神経周囲から視交叉にかけてT2強調画像で高信号領域を認め，視路視床下部毛様細胞性星細胞腫と診断した。現在は視機能に増悪傾向がなく，慎重に経過観察している。

結論：弱視治療に抵抗する場合，積極的にMRIで頭蓋内の検索をする必要があると思われた。

Abstract　Purpose：We report a case of optic hypothalamic pilocytic astrocytoma detected during amblyopia treatment in a child.

Case：An 11-month-old boy presented with mild nystagmus was presented at the first visit. No abnormality was detected in the anterior segment, ocular media, or fundus of the eye, and his eye movement was good. At the age of 2 years and 9 months, left visual acuity was poor, farsightedness was present, we diagnosed left unequal amblyopia, and started treatment for amblyopia with spectacles. However, his visual acuity did not improve, and his eye position deteriorated from intermittent exotropia to constant exotropia. During this treatment, he had neither an apparent relative afferent pupillary defect（RAPD）nor proptosis. Brain MRI was performed at the age of 5 years. A high-intensity area was observed from the left optic nerve to the optic chiasm and the posterior internal capsule on T2-weighted images and optic hypothalamic pilocytic astrocytoma was diagnosed. Although there is no tendency toward deterioration of visual function, the patient should be carefully and routinely monitored.

Conclusion：Examination of brain MRI scans should be proactively in case of treatment-resistant amblyopia.