A Case of Normal-pressure Hydrocephalus Caused by Cauda Equina Capillary Malformation.

Capillary malformations in the central nervous system, especially in the cauda equina, are rare. Although the typical symptoms are lower back pain and motor weakness in the lower extremities, we report here a rare case in which the initial symptom of a capillary malformation in the cauda equina was normal-pressure hydrocephalus. A 67-year-old woman was admitted to our hospital for close examination of hydrocephalus. Imaging studies showed no abnormalities other than an 8-mm intradural extramedullary tumor at the lumbar 2 level. Given lumbar puncture revealed a high protein level and the pressure was within the normal range, we assumed the hydrocephalus was caused by a schwannoma in the cauda equina. Within 7 days after admission, the patient's consciousness level decreased rapidly. Therefore, we immediately placed a ventriculoperitoneal shunt. Nine months after admission, the tumor increased from 8 mm to 12 mm in diameter, and tumor resection was performed. Because intraoperative neuromonitoring revealed that the tumor arose from a motor nerve, and the appearance of the tumor was not that of a typical schwannoma, we decided to remove the tumor subcapsularly. The pathological diagnosis was a capillary malformation. No neurological deficits developed in the patient postoperatively, and the high cerebrospinal fluid protein level normalized after the tumor resection. Although hydrocephalus caused by a capillary malformation in the cauda equina is relatively rare, it should be differentiated, and the strategy for its resection should be considered using the information obtained from preoperative neurological symptoms and intraoperative neuromonitoring.