Mondo Description A rare syndrome affecting conjugate vertical eye movement. It is often caused by a dorsal midbrain neoplasm, commonly a pinealoma, but may also be attributable to demyelinating diseases or stroke. Clinical signs include limitation of upward gaze, light-near dissociation of the pupillary response, eyelid retraction (Collier's sign) and convergence-retraction nystagmus. Clinical course is dependent on effective treatment of underlying cause.