Pupil involvement appears common in diabetes-associated oculomotor nerve palsy

This prospective study found that pupil involvement occurs in about one-fourth of all diabetes-associated oculomotor nerve palsy cases and ophthalmoplegia resolves much earlier than anisocoria in these patients.

Subjects were 35 consecutive patients with diabetes-associated oculomotor nerve palsy.

Pupillary involvement was present in 25.7 percent of the patients, all of whom had 1 mm to 2 mm of anisocoria. Ophthalmoplegia improved much earlier and more significantly than anisocoria.

The authors note that most patients developed maximum anisocoria within the first two weeks after the onset of symptoms. However, patients were not followed up on a daily basis, and if they had been, the maximum anisocoria might have been detected at a much earlier stage.

While one patient was lost to follow-up, pupils normalized in a majority of patients (55.5 percent). The direct pupillary reaction, which was impaired during the initial two visits, normalized or near normalized as the ophthalmoplegia reversed and the pupil returned to its original size. The majority of subjects in both pupil-involved and pupil-spared groups showed a recovery of ophthalmoplegia over the initial two visits.

They say that imaging should be considered in cases of pupil-involved oculomotor nerve palsies with additional cranial nerve palsy or neurological abnormalities and in which pupils show characteristics of a compressive lesion, even if their history is suggestive of an ischemic lesion.

They conclude that certain pupil characteristics, like an incomplete involvement and anisocoria < 2 mm, may help to distinguish diabetic (ischemic) from aneurysmal (compressive) injury of the oculomotor nerve, even though the pupil may be involved in both.