JKOS Journal of the Korean Ophthalmological Society J Korean Ophthalmol Soc 0378-6471 2092-9374 Korean Ophthalmological Society 10.3341/jkos.2018.59.4.388 jkos-59-388 Case Report Abducens Nerve Palsy Caused by the Ophthalmic Segment of an Internal Carotid Artery Aneurysm KimInhyeMD1 KimJong HoonMD2 KimWon JaeMD1 Department of Ophthalmology, Yeungnam University College of Medicine, Daegu, Korea Department of Neurosurgery, Yeungnam University College of Medicine, Daegu, Korea Address reprint requests to Won Jae Kim, MD Department of Ophthalmology, Yeungnam University Hospital, #170 Hyeonchung-ro, Nam-gu, Daegu 42415, Korea Tel: 82-53-620-4191, Fax: 82-53-626-5936, E-mail: eyekwj@ynu.ac.kr 92018 792018 59 4 388 392 9112017 5122017 22032018 Copyright © 2018 Korean Ophthalmological Society 2018 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 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.

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Images of the patient in nine diagnostic position of gaze at initial visit. The patient showed esotropia at primary gaze with abduction limitation of the left eye.

Images of cerebral digital subtraction angiography (DSA) during treatment. (A) Cerebral DSA showed ophthalmic segment aneurysm of left internal carotid artery (neck: 2.80 mm, height: 3.33 mm, width: 3.31 mm, posterior-inferior direction). (B) Cerebral DSA showed two microcatheters were located in the aneurysm. (C, D) Cerebral DSA showed coil embolization was finished with no abnormal findings.

Images of the patient in nine diagnostic position of gaze at 3 months after the treatment. The patient showed stable ocular alignment without diplopia.