画像検査で診断が困難であった視神経管骨折の1例

A case of optic canal fracture with difficulty in diagnostic imaging

要約　目的：画像診断では確認できず，手術で視神経管骨折が発見された症例の報告。症例：33歳男性が自転車で走行中，右から来た自転車と衝突して頭部の右側を打撲し，右眼の視力低下を自覚して受診した。所見：矯正視力は右0.4，左1.5であり，右眼に下半分と上耳側の視野欠損があった。CTなどの画像検査で右中頭蓋窩に血腫，右眼窩底と右頰骨に骨折があり，視神経管骨折は同定されなかった。3日間のステロイドパルス療法を施行したが視力が0.2に低下した。脳神経外科で開頭手術を行い，右視神経管骨折が発見された。2か月後の現在，視野はやや拡大し，視力は0.3で，乳頭の蒼白化がある。結論：頭部外傷に続発した視神経症で，薬物療法によっても視力や視野が悪化するときには，画像診断の裏づけがなくても視神経管骨折がある可能性がある。

Abstract.　Purpose：To report a case of optic canal fracture that could not be detected by diagnostic imaging and that was diagnosed during surgery. Case：A 33-year-old male was running a bicycle and was hit by another bicycle coming from the right side. He was injured on the right side of the head followed by decreased visual acuity in his right eye. Findings：His corrected visual acuity was 0.4 right and 1.5 left. The right eye showed visual field defect in the lower hemisphere and upper left quadrant. Diagnostic imaging,including computed tomography and magnetic resonance imaging（MRI）,showed intracranial hematoma and fractured maxillary bone. Brain surgery was performed 3 days later after visual acuity further decreased following massive corticosteroid therapy. Optic canal fracture was detected as intraoperative finding. Conclusion：This case illustrates that optic canal fracture may be present following head injury even with negative findings by diagnostic imaging.