Light-induced Hemiplegia, an Atypical Case of Retinal Steal Syndrome David Kerek, MD,* Sami Al Kasab, MD,* Michael U. Antonucci, MD,w Raymond D. Turner, IV, MD,z and Tanya N. Turan, MD, MS* Abstract: Atherosclerosis affecting the carotid arteries accounts for up to 20% of ischemic strokes 1. The clinical effects of atherosclerotic occlusive disease vary according to multiple factors, one of which is collateral circulation. In response to a chronic decrease in cerebral perfusion from atherosclerotic occlusion, alternative flow pathways, or collaterals, develop in a variety of patterns. In the setting of carotid occlusion, flow from the Circle of Willis, if complete, often comprises the main cerebral collateral network. In addition, contributions from leptomeningeal and extracranial to intracranial collaterals may develop. In the latter, reversal of flow in the ophthalmic artery can reconstitute to restore supraclinoid internal carotid artery flow. We report a case of the unusual sequela of a collateral flow pattern via the ophthalmic artery that induces a unique retinal steal phenomenon. Key Words: stroke, ICA occlusion, retinal steal (The Neurologist 2017;22:57–60) A therosclerosis affecting the carotid arteries accounts for up to 20% of ischemic strokes. 1 The clinical effects of athe- rosclerotic occlusive disease vary according to multiple fac- tors, one of which is collateral circulation. In response to a chronic decrease in cerebral perfusion from atherosclerotic occlusion, alternative flow pathways, or collaterals, develop in a variety of patterns. In the setting of carotid occlusion, flow from the Circle of Willis, if complete, often comprises the main cerebral collateral network. In addition, contributions from leptomeningeal and extracranial to intracranial collaterals may develop. In the latter, reversal of flow in the ophthalmic artery can reconstitute to restore supraclinoid internal carotid artery (ICA) flow. We report a case of the unusual sequela of a collateral flow pattern via the ophthalmic artery that induces a unique retinal steal phenomenon. CASE REPORT A 62-year-old white male with a past medical history of obesity, hypertension, hyperlipidemia, obstructive sleep apnea, chronic kidney disease, pulmonary embolism, and ischemic cerebrovascular accident presented with transient, recurrent episodes of left arm and leg weakness, along with blurry vision in his left eye. These symptoms lasted 10 to 15 minutes with return to baseline thereafter. The patient specifically noted that these episodes were precipitated by light exposure, particularly when driving in bright sunlight. His work-up included a magnetic resonance imaging (MRI) of the brain, which showed stable encephalomalacia with surrounding gliosis in the right frontal lobe from a remote infarction of the anterior border zone region (Fig. 1). His magnetic resonance angiogram head and neck with and without contrast showed no appreciable forward flow in the right ICA (Figs. 2, 3). Catheter angiography showed complete occlusion of the right ICA, multiple small (< 0.5 mm each) ethmoidal artery collaterals feeding the ophthalmic artery, which, in turn, partially supplied the distal right ICA and part of the right M1 segment of the middle cerebral artery (MCA). However, this collateral pathway was insufficient, with a notable lack of opacification of the right A1 segment of the anterior cerebral artery and MCA branches distal to M1 (Fig. 4). Minimal MCA collateral flow from the right posterior communicating artery and from posterior cerebral artery (PCA) pial collaterals was also identified, but the lack of a discrete, complete capillary phase indicated overall poor flow in the MCA territory. Coupled with the chronic border zone ischemic change, the angiographic findings were suggestive of an underlying diminished cerebrovascular reserve (CVR) due to the chronic ICA occlusive dis- ease. Of note, transcranial Doppler also confirmed retrograde flow in the right ophthalmic artery (Fig. 5). The MRI included arterial spin labeled (ASL) perfusion imaging. This demonstrated asymmetric arterial transit artifact in the right MCA vasculature and, conversely, little signal in the brain parenchyma itself (Fig. 6). This indicates diminished and delayed flow in the right ICA territory with transit of labeled blood markedly delayed relative to the contralateral hemisphere. In addition, delayed transit was noted in his PCA collateral vasculature. The combination of insufficient native flow in his MCA and delayed flow within recruited pial collateral vessels, coupled with a known CVR impairment, underscores the importance of the ophthalmic collateral flow in maintaining his baseline, asympto- matic status. The patient was initially treated with intensive medical therapy, which included aspirin 325 mg daily and atorvastatin 80 mg daily. However, as his symptoms persisted, and given the relatively poor collateral flow to the MCA territory, the patient underwent a right- sided craniotomy for indirect external carotid artery to ICA bypass, in the form of an encephaloduroarteriomyosynangiosis. Postoperatively, the patient’s course was complicated by incisional infection, and transient dizziness in the setting of hypotension. He also experience left upper extremity and lower extremity limb shaking with preserva- tion of consciousness observed at an outside hospital 1 month after the procedure. An electroencephalogram was performed at the time, which did not show any epileptiform activity, but he was started on an antiepileptic (levetiracetam). Several months later, the patient developed similar episodes that began with tingling in his left leg that travels up to his hip and left hand followed by weakness on the left side, then shaking of the left arm and leg that was sometimes subtle, sometime violent. He denied loss of consciousness, tongue biting, bowel incontinence or bladder incon- tinence, and vision change during these spells. The episodes last for a few minutes and occur 2 to 3 times per week and are always associated with a decrease in his hemoglobin to <9 gm/dL due to chemotherapy (required for newly diagnosed malignancy). Repeat MRI did not show any evidence of new cerebrovascular accident. His episodes of left- sided weakness provoked by bright light resolved. DISCUSSION Although it is common for patients with internal carotid occlusion to develop collateral pathways through the From the Departments of *Neurology; wRadiology; and zNeurosurgery, Medical University of South Carolina, Charleston, SC. The authors declare no conflict of interest. Reprints: Tanya N. Turan, MD, MS, MUSC Stroke Program 19, Hagood Avenue, Suite 501, Harborview Office Tower, Charleston, SC 29425. E-mail: turan@musc.edu. Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1074-7931/17/2202-0057 DOI: 10.1097/NRL.0000000000000109 CASE REPORT/CASE SERIES The Neurologist  Volume 22, Number 2, March 2017 www.theneurologist.org | 57 Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.