Superior Division Oculomotor Nerve Palsy and Diabetes Mellitus: A Case Report

Oculomotor nerve (third cranial nerve) palsy is a neuro-ophthalmic emergency that can signify life-threatening pathologies. Diabetes mellitus (DM) is a common cause of isolated oculomotor palsies. We report a case of an acute isolated ptosis and diplopia caused by a superior division oculomotor nerve palsy in a diabetic patient, highlighting the diagnostic approach and outcome. A 59-year-old man with type 2 DM and dyslipidemia presented with acute right upper eyelid drooping and binocular diplopia, without headache or other neurological symptoms. Examination revealed complete right-sided pupil-sparing blepharoptosis and inability to elevate the right eye, causing vertical diplopia on upward gaze. All other extraocular movements were intact. No other neurological deficits were present. Laboratory workup was unremarkable, except for a glycated hemoglobin (HbA1c) of 7.1%, indicating suboptimal glycemic control. Urgent neuroimaging of the brain and orbits was performed and showed no intracranial lesions. The findings were consistent with a superior division oculomotor nerve palsy due to diabetic microvascular ischemia. Management was conservative, and by the one-month follow-up, the patient's ptosis and diplopia had resolved with recovery of ocular motility. This case illustrates a pupil-sparing partial oculomotor nerve palsy attributable to diabetic microangiopathy, which can mimic more ominous causes of third nerve palsy. It underscores the importance of recognizing the characteristic features of superior divisional third cranial nerve palsy while still promptly excluding compressive etiologies with appropriate imaging. With proper risk factor management, ischemic diabetic third nerve palsies carry an excellent prognosis, often with complete recovery within three months. Early diagnosis and conservative management in such cases lead to full neurological recovery and prevent unnecessary invasive interventions.