Binocular diplopia in partial unilateral oculomotor nerve (Ocn) palsy

Background: Binocular diplopia is mostly caused by oculomotor nerve (OCN) palsy. Acquired OCN palsy has varied etiolo-gies, therefore managing OCN palsy depends on the cause and presence of amblyopia. Aim: To report a case of binocular diplopia associated with unilateral OCN palsy. Case Illustration: A 49-year-old male patient presented with the first episode of binocular diplopia. He had histories of cardi-ac catheterization and dyslipidemia. Ophthalmology examination showed exotropia of the left eye with no pupillary involve-ment, and isolated paresis of left OCN the medial rectus muscle. Laboratory studies showed high level of total cholesterol and low-density lipoprotein (LDL). We found his left OCN was in contact with left P2A posterior cerebral artery (PCA) segment, suggesting a neurovascular conflict during MRI. Steroid along with antiplatelet and statin were given. Each eye was occluded with patch every 3 hours alternately during hospital treatment. The symptoms improved and he had no complaint in the following 3 months after the event. Discussion: The most common cause of partial third nerve palsy is microvascular. Vascular anomalies could compress the oculomotor nerve, inducing irritation of the nerve. Conclusion: This case suggests neurovascular conflict as the cause of diplopia due to partial unilateral OCN palsy.