Bilateral isolated sixth cranial nerve palsy after unilateral intravitreal Ranibizumab injection: Case report and review of literature

Abstract

Ranibizumab is an anti-vascular endothelial growth factor agent that has revolutionized the treatment of diabetic macular edema. Although the systemic safety profile of ranibizumab is generally favorable, it could rarely cause adverse effect such as microvascular cranial nerve palsy. A 68-year-old man who has right centrally-involved diabetic macular edema presented with binocular diplopia and squint five days after his first dose of intravitreal ranibizumab injection. His pupils were equal and reactive to light with no relative afferent pupillary defect. Hirschberg test revealed bilateral esotropia at primary gaze, while ocular motility exam showed bilateral abduction deficit. Bilateral lateral rectus palsy was further confirmed with Hess test. Other neurological examination was negative. Given the recent intravitreal ranibizumab injection, the bilateral sixth cranial nerve palsy was attributed to ranibizumab injection causing microvascular complication. The lateral rectus function improved at 3-month follow up. This is the first case report of bilateral sixth cranial nerve palsy that developed following intravitreal ranibizumab injection. We propose that the unilateral intravitreal ranibizumab injection has triggered a systemic microvascular disturbance, resulting in bilateral abducens nerve ischemia.