Arachnoid cyst of the quadrigeminal cistern.

Arachnoid cysts of the quadrigeminal region are rare. We report two new cases. The first is a 29-year-old woman, who had a recurrence five years after sub-total removal of the cyst wall. Initially it was communicating and was treated by a ventriculo-atrial shunt; later it became noncommunicating and direct drainage of the cyst cavity was required. The second was a 25-year-old female, successfully treated by wide removal of the cyst wall thus creating a large communication with the subarachnoid space. Diagnosis of these lesions, as regards either morphological or functional features, nowadays rests largely on CT. Choices about treatment are extremely difficult. The most radical one, namely, complete removal of the capsule, is not without risks and disadvantages. More prudent methods, such as partial removal of the capsule and/or drainage of the cyst and the ventricles, seem on the whole to be preferable, but careful pre- and post-operative evaluation of CSF dynamics are essential for a satisfactory and long-lasting outcome.