Hemorrhagic complication of arachnoid cyst: A case report and literature review.

Arachnoid cysts (ACs) are congenital malformations that can form anywhere in the subarachnoid space along the cerebrospinal axis. While intracystic hemorrhage and subdural hematoma (SDH) are rare, they can be urgent complications that may require emergency craniotomy. This report aims to present a case of an AC complicated by intracystic hemorrhage and SDH. A 63-year-old man presented after a fall, reporting a mild headache, right-sided weakness, confusion, speech difficulties, and gait ataxia. Brain magnetic resonance imaging (MRI) revealed an acute or early subacute SDH. A cystic structure measuring 9 × 6 × 5 cm and showing hemorrhagic characteristics was identified deep within the left SDH. The patient underwent a left-sided craniotomy to evacuate the SDH and remove all surrounding membranes. Additionally, an intracystic hematoma was evacuated, and the cyst wall was fenestrated. The patient remained stable during the follow-up. Over the past decade, a brief literature review on AC complicated by intracystic hemorrhage and SDH identified 9 case reports encompassing ten cases. Patient ages ranged from 6 to 47 years, with only 2 (20%) female patients. Headaches were the most frequent symptom, present in all patients, while eight patients (80%) had no history of head trauma. Only two cases (10%) were treated conservatively. In conclusion, individuals with AC are vulnerable to developing intracystic hemorrhage and SDH, either spontaneously or post-trauma. Open craniotomy combined with cyst fenestration can lead to preferred outcomes in treating this condition.