Hydrocephalus induced by low cerebrospinal fluid (CSF) pressure is extremely rare and sporadically reported. Subarachnoid hemorrhage, head trauma, and spinal drainage were reported to be causative factors for surgical treatment. A 33-year-old man with subarachnoid hemorrhage caused by right vertebral artery aneurysm rupture developed headache. Trapping surgery was performed, and a spinal drain was inserted from L4/5 for subarachnoid hemorrhage washout. On postoperative day 3, subdural fluid

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... mulation had increased at the posterior fossa craniotomy site and the cerebellar sulci had narrowed; the ventricles were slightly enlarged. The patient reported headache during head elevation. Low-pressure hydrocephalus (LPH) was suspected. After the spinal drain was removed, headache resolved, and cerebral ventriculomegaly disappeared. The subsequent clinical course was good. The patient was discharged 3 weeks after surgery. LPH is a rare disease caused by various factors and is treated by correcting liquorrhea or overdrainage, when present. Otherwise, drainage at negative CSF pressure is necessary. The symptoms and image findings for LPH are similar to those for intracranial hypertension and normal-pressure hydrocephalus. This report describes a suspected case of LPH caused by spinal drainage after subarachnoid hemorrhage and reviews the literature.