Asymptomatic arachnoid cysts turning symptomatic after sports-related concussion injury: a report of two cases.

Arachnoid cysts are usually asymptomatic, and the mechanisms leading to symptomatic presentation remain unclear. Although post-traumatic onset has been reported, it is often related to hemorrhagic complications such as chronic subdural hematoma. Prolonged post-concussive symptoms in children are clinically significant; however, reports linking such symptoms to arachnoid cysts without hemorrhage are rare. Case 1: A 17-year-old male developed headache and dizziness after being struck on the head during baseball practice. Imaging revealed a middle cranial fossa arachnoid cyst without traumatic changes. He was initially managed conservatively, but symptoms persisted for four months and progressively worsened, preventing practice participation. Craniotomy with cyst fenestration resulted in complete symptom resolution and return to training. Case 2: A 15-year-old female developed similar symptoms after colliding with a teammate during a softball game. Imaging showed a posterior cranial fossa arachnoid cyst without traumatic changes. Conservative management failed as symptoms persisted for four months, precluding sports participation. Craniotomy with cyst fenestration led to full recovery and return to training. In both cases, previously asymptomatic arachnoid cysts became symptomatic after head trauma, presenting with prolonged concussion-like symptoms although no traumatic changes were observed on imaging. Symptoms resolved immediately after surgical intervention. These cases may suggest that their prolonged concussion-like symptoms derived from arachnoid cysts and highlight the importance of careful clinical observation and operative indication.