Convergence-retraction nystagmus in Parinaud's syndrome

Dorsal midbrain (Parinaud's) syndrome often consists of upgaze paresis, convergence-retraction nystagmus (CRN), pupillary light-near dissociated, and eyelid retraction. Patients may have a selective upward saccade palsy with sparing of upward pursuit and the vestibulo-ocular reflex, or the inability to make any upward movements. When patients are asked to look up, instead of an upward saccade, the eyes may converge, relax, converge, etc. These alternating convergent-divergent movements give the appearance of nystagmus, even though it is not technically nystagmus. This is probably another manifestation of disinhibited or overactive convergence, and if the globes are viewed from the side, a retraction into the orbits can be seen due to co-contraction of extraocular muscles. An optokinetic stimulus (e.g., drum or flag) is a convenient way to visualize the CRN because it will occur with each (attempted) under quick phase. This patient had a history of craniopharyngioma and hydrocephalus, which are etiologies that can cause external compression of the dorsal midbrain and posterior commissure. There was also light-near dissociation and eyelid retraction was also noted acutely, but improved with time. The left eye is being occluded in this video due to a longstanding (unrelated) large angle comitant exotropia, to ensure that the strabismus did not interfere with the finding of CRN.