腎細胞癌の眼窩転移による球後視神経症が疑われた1例

A case suspected of retrobulbar optic neuropathy secondary to orbital metastasis of renal cell carcinoma

要約　目的：腎細胞癌の眼窩円錐部への転移による球後視神経症が疑われた1例の報告。

症例：65歳，男性。腎細胞癌に対し化学療法中，右視力低下を自覚し当科に紹介され受診した。初診時所見は，右眼矯正視力0.01，眼圧18.3mmHg，対光反応で右眼に相対的瞳孔求心路障害を認めた。眼底所見は異常なく，Goldmann視野検査で右眼に下方水平半盲を認め，右眼の中心フリッカ値は低値であった。造影MRIで眼窩円錐部に造影効果のある腫瘤影を認め視神経を圧排していた。臨床的に腎細胞癌による眼窩転移と診断し，ステロイドパルスおよび局所放射線治療を行った結果，腫瘍は縮小し矯正視力は0.04まで回復し，視野検査における水平半盲は軽快した。

結論：腎細胞癌の眼窩転移による球後視神経症に対して，局所放射線治療が有効であった。

Abstract　Purpose: To report a case suspected of retrobulbar optic neuropathy secondary to metastasis of renal cell carcinoma to the orbital apex.

Case: A 65-year-old man was referred to us for right visual loss. He had been diagnosed with renal cell carcinoma 20 months before and been treated by systemic chemotherapy.

Findings: Best corrected visual acuity was 0.01 right and 1.2 left. Funduscopy showed normal findings in either eye. The right eye showed inferior horizontal hemianopia and reduced critical flicker frequency. Gadolinium-enhanced magnetic resonance imaging（MRI）showed a mass lesion in the orbital apex. Corticosteroid pulse therapy followed by radiation resulted in improved visual acuity and visual field. There has been no recurrence for 6 months until present.

Conclusion: The present case illustrates that the orbit may be affected by metastasis of renal cell carcinoma and may result in clinical manifestation mimicking retrobulbar optic neuropathy. Radiotherapy was effective for orbital metastasis.