自然緩解した眼窩内骨膜下血腫の1例

A case of orbital subperiosteal hematoma with spontaneous resolution

34歳女性が歩行中にオートバイと接触し，脳挫傷と急性硬膜下血腫による昏睡状態になった。受傷から14日後の磁気共鳴画像検査（MRI）で，骨壁に沿い水平線（ニボー）のある紡錘形の病変が発見され，眼窩内骨膜下血腫と診断された。昏睡から回復後に複視を自覚し，受傷から19日後に受診した。左眼に上転障害と眼瞼下垂があった。視力と視野には異常がなかった。格別の治療なしに受傷から49日後に複視が消失し，軽度の眼瞼下垂のみが残った。MRIでみられたニボーは，血腫中のヘモグロビンが14日間に変性し，下方のデオキシヘモグロビンと上方のメトヘモグロビンに分かれたためと推定した。

A 32-year-old woman was hit by a motorcycle while walking. She became comatous due to cerebral contusion. Magnetic resonance imaging（MRI）was performed on day 14 of injury. A crescent-shaped lesion,showing a niveau,was present in the supraorbital frontal bone. The finding was suggestive of subperiosteal hematoma of the orbit. She complained of diplopia when recovering from coma. When seen by us on day 19 of injury,her left eye showed restricted elevation and blepharoptosis. There was no abnormality in the visual field or acuity. The limited eye movement and diplopia spontaneously resolved on day 49 of injury,leaving moderate blepharoptosis. The niveau seen in the hematoma was probably due to degeneration of hemoglobin into methemoglobin and deoxyhemoglobin during 14 days after injury. The latter would have settled in the inferior portion of hematoma because of greater specific gravity.