[Neuro-endoscopic Management of Intraparenchymal Arachnoid Cyst in Adults:Three Case Reports].

We report 3 cases of symptomatic intraparenchymal arachnoid cysts in adults, including 2 in elderly patients. Case 1:An 81-year-old woman developed right-sided hemiparesis and hemianopsia due to the enlargement of left occipital arachnoid cyst, which had been incidentally diagnosed 3 years ago. Under the guidance of neuronavigation, we inserted a rigid endoscope into the cyst and perforated the cyst wall toward the posterior horn of the lateral ventricle, making a good communication between the cyst and the ventricle for cerebrospinal fluid. Her symptoms improved within 3 days after the surgery, and the cyst mass reduced. Case 2:A 57-year-old woman was incidentally found to have a right frontal arachnoid cyst. She had a 3-month long history of low mood and loss of interest in work. We perforated the transparent septum via the cyst wall toword the left lateral ventricle in a neuro-endoscopic procedure. After the surgery, she regained interest in work, and her symptom was considered to be indicative of depression due to arachnoid cyst. Case 3:A 94-year-old woman in a geriatric facility developed left-sided hemiparesis due to the enlargement of a right temporal arachnoid cyst, which had been detected 10 years ago. Neuro-endoscopic perforation of the cyst wall toward the lateral ventricle remarkably improved her symptoms. Arachnoid cysts can become symptomatic in the long term, not only in the young but also in the elderly. Neuro-endoscopic fenestration is an effective treatment for symptomatic intraparenchymal cysts, especially in elderly patients. The neuronavigation system was useful in the planning of the trajectory and in the detection of the target point of fenestration.