Spontaneous resorption of a convexity arachnoid cyst associated with intracystic hemorrhage and subdural hematoma: A case report.

Background: Intracranial arachnoid cysts (ACs) are developmental anomalies usually filled with cerebrospinal fluid (CSF), rarely resolving throughout life. Here, we present a case of an AC with intracystic hemorrhage and subdural hematoma (SDH) that developed after a minor head injury before gradually disappearing. Neuroimaging demonstrated specific changes from hematoma formation to AC disappearance over time. The mechanisms of this condition are discussed based on imaging data. Case Description: An 18-year-old man was admitted to our hospital with a head injury caused by a traffic accident. On arrival, he was conscious with a mild headache. Computed tomography (CT) revealed no intracranial hemorrhages or skull fractures but an AC was seen in the left convexity. One month later, follow-up CT scans showed an intracystic hemorrhage. Subsequently, an SDH appeared then both the intracystic hemorrhage and SDH gradually shrank, with the AC disappearing spontaneously. The AC was considered to have disappeared, along with the spontaneous SDH resorption. Conclusion: We present a rare case where neuroimaging demonstrated spontaneous resorption of an AC combined with intracystic hemorrhage and SDH over time, which may provide new insights into the nature of adult ACs.