Spontaneous Subdural Fluid Collection Following Aneurysmal Subarachnoid Hemorrhage: Subdural Hygroma or External Hydrocephalus?

Subdural fluid collections (hygromas and effusions) in adults are usually seen following head trauma or overdrainage of cerebrospinal fluid (CSF) after CSF diversion procedures. We report an unusual case of subdural fluid collection that developed spontaneously 5 days after an aneurysmal subarachnoid hemorrhage (SAH). This patient neither had permanent CSF diversion procedure nor history of significant head trauma during her clinical course. This study is a Case report of the patient suffering from an SAH. A 71-year-old woman suffered an SAH from a ruptured right-sided posterior communicating artery aneurysm. Computed tomography (CT) demonstrated diffuse SAH and signs of early hydrocephalus that did not require treatment. The aneurysm was treated with endovascular coil occlusion without any complications. Throughout her hospital course, she remained alert without neurological deficits. A large subdural fluid collection was discovered incidentally during a routine CT scan of the brain 5 days after the SAH. The patient remained asymptomatic; therefore, the collection was treated conservatively. It resolved spontaneously at five days after the initial diagnosis. Subdural fluid collections following SAH can occur as a result of head trauma, external hydrocephalus, or as a treatment complication of CSF shunting and craniotomies. It is critical to differentiate simple hygromas from external hydrocephalus since their response to CSF diversion is entirely different.