Abducens Nerve Palsy Caused by the Ophthalmic Segment of an Internal Carotid Artery Aneurysm

ABSTRACT

PURPOSE: To report a case of isolated abducens nerve palsy caused by the ophthalmic segment of an internal carotid artery (ICA) aneurysm which improved after endovascular coil trapping. CASE SUMMARY: A 59-year-old female visited the ophthalmology department for a sudden onset of horizontal diplopia for 10 days. The best corrected visual acuity was 20/20 in both eyes. The pupils showed normal response to light and near stimulation in both eyes. The extraocular examination showed 35 prism diopters left esotropia at primary gaze and −4 abduction limitation of the left eye. The patient suffered intermittent headaches in the left temporal area and left retrobulbar pain for 1 month. Magnetic resonance imaging with magnetic resonance angiography of the brain was performed. A focal protruding lesion of the left ICA suggested an aneurysm. The patient consulted with the neurosurgery department. The left ophthalmic segment of the ICA aneurysm was confirmed by transfemoral cerebral angiography and treated with coil placement and the patient showed gradual improvement after the procedure. Three months after the procedure there was no diplopia. The patient showed orthotropia at primary gaze without abduction limitation. CONCLUSIONS: Isolated abducens nerve palsy can be caused by the ophthalmic segment of an ICA aneurysm, which should be considered in the differential diagnosis of ocular motility disorders. The disorder improved with coil replacement treatment. Differential diagnosis as a cause of abducens nerve palsy is important for prompt and appropriate treatment. Neuroimaging should be considered in patients with isolated abducens nerve palsy with a non-ischemic origin.