Arachnoid cysts (ACs) are intra-arachnoid collections of cerebrospinal fluid (CSF). Primary congenital lesions within the arachnoid membrane that expand by CSF secretion (1). ACs that exert a mass effect, particularly those in children, should be treated. Surgical options include drainage by needle aspiration or burr hole evacuation; craniotomy for cyst excision or marsupialization into the subarachnoid space, basilar cisterns, or ventricles; and cyst-peritoneal shunting (2). The management of asymptomatic individuals, who present with large cysts, is controversial. Cerebral SPECT shows impaired brain perfusion in 70% of symptomatic patients. The zone of decreased rCBF corresponds well with clinical symptoms and with neuroimaging findings. Constitutes a valuable adjunct tool for correlating regional function with brain anatomy, and may be of help to allocate patients with ACs for surgical treatment or clinical observation. (3) .