Spontaneous rupture of an arachnoid cyst with subdural hygroma formation: a rare case report and literature review.

BACKGROUND

Arachnoid cysts are congenital, cerebrospinal fluid-filled sacs, predominantly asymptomatic and often detected incidentally. Spontaneous rupture of arachnoid cysts is an exceedingly rare complication, particularly in pediatric patients, and may present with acute neurological symptoms, including cranial nerve palsies.

CASE PRESENTATION: We report a 7-year-old male with a large, left middle fossa arachnoid cyst, initially asymptomatic and followed conservatively for five years. The patient developed resistant headache, vomiting, and right sixth cranial nerve palsy. Neuroimaging revealed spontaneous cyst rupture with resultant subdural hygroma and midline shift. The patient underwent successful endoscopic cyst fenestration with significant symptomatic improvement and complete resolution of cranial nerve palsy at six-month follow-up.

LITERATURE REVIEW: A review of the literature identified fewer than ten pediatric cases of spontaneous arachnoid cyst rupture associated with cranial nerve deficits. Trauma is the most commonly reported precipitant; however, non-traumatic rupture mechanisms such as increased intracranial pressure have been postulated. Surgical intervention remains the mainstay treatment in symptomatic ruptures, typically yielding favorable outcomes.

CONCLUSION

Spontaneous rupture of arachnoid cysts, although rare, should be considered in patients presenting with new neurological symptoms during follow-up. Early recognition and prompt surgical management are essential to prevent potentially severe complications. Close clinical surveillance is recommended even in asymptomatic cases to detect subtle clinical changes indicative of rupture.