Dorsal midbrain syndrone & shunt dysfunction

Synonyms-- pretectal syndrome, Parinaud syndrome, syndrome of the superior colliculus.

Signs and symptoms classically include vertical gaze palsy, pupillary light-near dissociation, convergence-retraction nystagmus, lid retraction, and abnormalities of convergence and accomodation. Early on, however, one may see only conjugate upgaze paresis, involving only saccades and not smooth pursuit movements. Gaze evoked upbeat nystagmus, with intact reflex upgaze. Children who complain of trouble seeing near objects should be tested for upwards saccades, as these patients may be likely ot have pineal cysts or hydrocephalus, or if they have a ventriculoperitoneal shunt, shunt dysfunction.

In evaluation for shunt dysfunction, patients may have not only abnormal velocity and accuracy of upwards saccades, but also a sixth nerve palsy, nystagmus, esotropia, convergence spasm, and amblyopia consequent to visual loss from papilledema. According to Purvin et al, IT MAY TAKE CONSIDERABLE FORTITUDE TO INSIST ON THE DIAGNOSIS IN THE FACE OF ASSURANCES FROM THE RADIOLOGIST AND THE NEUROSURGEON THAT THE SHUNT IS WORKING PROPERLY.