Recurrent, Contralateral Pupil-Sparing Oculomotor (CN III) Mononeuropathy in Poorly Controlled Type 2 Diabetes Mellitus: A Case Report

Abstract

Diabetic cranial neuropathies are neurological complications that usually involve cranial nerves (CN) III, IV, and VI, causing acute onset ophthalmoplegia. Recurrence is less common, especially when affecting alternating nerves. The disease course is typically benign, with recovery over weeks to months. Recurrent, contralateral, pupil-sparing CN III palsy in a patient with poorly controlled diabetes supports a microvascular ischemic mechanism once compressive lesions are excluded. Microvascular cranial neuropathy occurs when there is blockage of blood flow to the cranial nerves, leading to nerve damage. This case highlights the importance of early neuroimaging, strict metabolic control, and clear documentation to prevent mislabeling as transient ischemic attack (TIA). We present a 53-year-old man with left periorbital headache, ptosis, and diplopia. The examination revealed a left pupil-sparing CN III palsy. He had an identical right-sided episode four years earlier that resolved spontaneously. Both episodes coincided with poor glycemic control. This case adds to the limited literature describing recurrent, alternating, pupil-sparing CN III palsy in diabetic patients.