くも膜下出血後水頭症に対するシャント術後に発症した片側posterior reversible encephalopathy syndrome（PRES）の1例

Unilateral Posterior Reversible Encephalopathy Syndrome after Ventriculo-Peritoneal Shunt for Normal Pressure Hydrocephalus Following Subarachnoid Hemorrhage:A Case Report

Ⅰ．はじめに

　Posterior reversible encephalopathy syndrome（PRES）は，臨床的に痙攣，意識障害，視覚異常などを主症候とし，画像上脳浮腫と考えられる変化が主に両側後部白質を中心に出現し，臨床症候や画像所見が可逆性という特徴をもった臨床的・神経放射線学的症候群である．誘因・発症機序については，高血圧，子癇などに伴い血管性浮腫（vasogenic edema）を生ずることで発症するとされている．

　PRESは通常両側性であり片側発症例は極めて稀であり，さらにシャント術が誘因と考えられる例の報告は渉猟し得た限り報告がない．今回われわれは，くも膜下出血後の水頭症に対するシャント術後に発症した片側PRESの1例を経験したため報告する．

　The patient, a 79-year-old man, experienced a Hunt ＆ Kosnik grade Ⅳ subarachnoid hemorrhage, presenting with sudden-onset coma and severe left hemiplegia. We performed cranial clipping surgery for a ruptured aneurysm on the right middle cerebral artery the same day. Post-operative recovery proceeded smoothly, with gradual improvements in disturbed consciousness and left hemiplegia. Three weeks post-operation, CT revealed low-density areas in the right frontal and temporal lobe, believed to be due to subarachnoid hemorrhage, as well as hydrocephaly. We then performed a lumbo-peritoneal（L-P）shunt for the hydrocephaly. Two months later, the patient experienced shunt occlusion, and we performed a ventriculo-peritoneal（V-P）shunt revision（pressure:6cm H₂O). Headaches, severe decline in cognitive function, and worsened left hemiplegia were observed seven weeks post-shunt revision. Cranial CT revealed widespread low-density areas in right posterior cerebral white matter. We suspected unilateral posterior reversible encephalopathy syndrome（PRES）after performing cranial MRI and cerebral angiography. Increasing the set pressure of the shunt improved the symptoms and radiographic findings.

　PRES is typically bilateral, and unilateral incidents are rare. This is the first report of unilateral PRES secondary to shunt operation. Its unilaterality appears to have been caused by unilateral brain damage or adhesions to the brain surface from the subarachnoid cerebral hemorrhage. Overdrainage post-shunt can also induce PRES. Diagnosis of PRES is more difficult in unilateral cases;practitioners must keep PRES in mind as a rare complication post-shunt operation.