[Selection of surgical approach for quadrigeminal cistern arachnoid cyst]

Preoperative magnetic resonance imaging of 4 cases of quadrigeminal cistern arachnoid cyst were retrospectively reviewed and patterns of extension to surrounding cisterns from the quadrigeminal cistern were examined. Relationship between patterns of extension to surrounding cisterns and selected surgical approach were evaluated. In 2 cases, the cyst extended anteriorly and compressed the quadrigeminal plate. These two cases had hydrocephalus due to aqueductal stenosis. The anteroirly extending cyst was treated with endoscopic ventriculocystocisternostomy via the lateral and third ventricles. In one case, the cyst extended superiorly to the velum interpositum cistern, and was treated with endoscopic ventriculocystocisternostomy via the lateral ventricle. In one case, the cyst extended laterally to the ambient cistern and compressed the posterior horn of the lateral ventricle. This case had loculated hydrocephalus of the inferior horn. The laterally extending cyst was treated with resection of the wall of the arachnoid cyst via an infratentorial supracerebellar approach assisted by endoscope. All cysts were successfully treated. Injury of the foramen of Monro occurred during a procedure using a flexible endoscope in a case with an anterior extending cyst. Exact analysis of the preoperative imaging and selection of appropriate surgical approach are key factors for successful treatment of a quadrigeminal cistern arachnoid cyst.