Multiple Sacral Perineurial Cysts Presented Symptoms Triggered by Nonaneurysmal Perimesencephalic Subarachnoid Hemorrhage.

The origin and pathogenesis of perineurial cysts remain unclear. Here, we report a rare case of multiple sacral perineurial cysts presented symptoms triggered by nonaneurysmal perimesencephalic subarachnoid hemorrhage (SAH). A 48-year-old male presented with a severe headache of sudden onset. Brain computed tomography revealed a SAH in the basal cistern; however, no abnormal vascular lesion was detected. Four days after the onset of the SAH, he suffered from left buttock pain, followed by urinary dysfunction and paresthesia in the left S2 and S3 dermatomes. Magnetic resonance (MR) imaging demonstrated multiple cystic lesions at the left S1 and bilateral S2 sacral roots. The two cysts at the S2 level exhibited high signal intensity on both T₁- and T₂-weighted images, suggesting the content of the cysts included a hematoma. He was treated with intravenous injections of steroids, and the symptoms recovered completely within 2 months. Follow-up MR imaging revealed remarkable shrinkage of the cysts. Sacral perineurial cysts should be listed in the differential diagnosis if the patient suffers from low back pain or sacral radiculopathy after the onset of SAH.