Symptomatic posterior fossa arachnoid cyst treated with endoscopic cystoventriculostomy in an adult.

We present a case of symptomatic posterior fossa arachnoid cyst (PFAC) that was successfully treated with endoscopic surgery. A woman in her 60s presented with progressive lightheadedness. Brain MRI showed a non-enhancing cystic lesion in the cerebellum that exerted pressure on the fourth ventricle, causing hydrocephalus, which further exacerbated 6 months later. Considering that PFAC was the cause of the patient's symptoms, an endoscopic cystoventriculostomy was performed. Postoperatively, the patient's symptoms improved, and MRI showed reduction of the cyst and improvement of hydrocephalus. Although symptomatic arachnoid cysts are uncommon in adults, endoscopic cystoventriculostomy is a minimally invasive and effective approach, with applicability across a broad spectrum of cases.