A Case of Subdural Hygroma due to a Ruptured Arachnoid Cyst in the Middle Cranial Fossa That Improved after Long-term Subdural Drainage: A Case Report and Review of the Literature.

Arachnoid cysts have the potential to rupture, leading to the development of a subdural hygroma following minor trauma. Although surgery may be considered in cases of increased intracranial pressure (ICP) or regional neurological symptoms, the optimal approach remains unclear. We report a case of subdural hygroma due to a ruptured arachnoid cyst (SHrAC) with elevated ICP successfully treated with long-term subdural drainage for over 1 month. A 26-year-old man with persistent headache was admitted to our hospital. Magnetic resonance imaging revealed an arachnoid cyst within the left middle cranial fossa and a subdural hygroma in the left frontotemporal region. He was referred to our neurosurgery department for surgical intervention due to elevated ICP. Although burr hole surgery was initially performed, subsequent recurrence of elevated ICP necessitated the insertion of a subdural peritoneal shunt. However, the shunt was then removed following the development of postoperative meningitis, and a subdural drain was placed to control ICP. Cerebrospinal fluid (CSF) drainage gradually decreased, and the elevated ICP improved. The subdural drain was removed approximately one and a half months after drain placement. The subdural hygroma progressively reduced and completely disappeared 4 months after drain removal. The gradual reduction in the pressure difference between the arachnoid cyst and the subdural hygroma due to long-term CSF drainage and inflammation caused by meningitis may have contributed to close arachnoid membrane laceration. Although alternative approaches, such as shunt insertion and basal fenestration, should always be considered in SHrAC treatment, long-term subdural drainage can be an option.