Torsional conjugate eye movements induced by pupillary light stimulation

A patient with a brain-stem mass and some evidence of brain-stem dysfunction showed torsional conjugate eye movements after eyelid opening in an illuminated environment, also on pupillary light stimulation. The response appeared after a latency period of 1-2 s, and occurred on stimulation of either the right or left eye. The ocular torsion was always bilateral and often conjugate. The phenomenon, however, varied in the extent, the direction and the symmetry of movement in the two eyes. It is probable that the phenomenon described was due to a disorder in the central, brain-stem mechanism, but the exact anatomical site and physiology are at present imprecise.