Tectal plate cyst in adults.

Tectal plate cysts are very rare. We report two adult patients with benign tectal plate cyst and secondary hydrocephalus. The first patient had an unusual eye movement disorder with bilateral upper eyelid retraction (Collier's sign), limited upgaze, severe upgaze evoked nystagmus and retraction nystagmus. The second patient presented with ataxia and failure of upward gaze. Endoscopic fenestration of the tectal plate cyst and endoscopic third ventriculostomy in both cases result in neurological improvement. To the best of our knowledge, similar lesions at this site have not been reported in adults. The differential diagnosis with arachnoid cysts of the quadrigeminal CSF cistern is discussed.