Isolated unilateral ptosis and mydriasis from ventral midbrain infarction

We report a patient who has a tremor and unilateral ptosis and mydriasis without extraocular muscle paresis from an intra-axial lesion demonstrated on neuroimaging. Previously extraocular muscles sparing partial third nerve palsy has been thought to be due to extra-axial lesion such as vascular compression. Compared to proposed models for arrangement of oculomotor fascicle, this case demonstrates that it is possible to damage the fibers destined for levator and pupillomotor function without affecting the extra-ocular muscles.