The authors obtained written informed consent from the patient. No approval from the IRB was sought as this article is a case report. The patient was a 65-year-old woman with a history of hypertension, hyperlipidemia, diabetes, atherosclerotic occlusion of the right subclavian artery and right femoral artery, and thoracic aortic aneurysm. She was admitted to our hospital with a complaint of the right hemiparesis (manual muscle testing [MMT] = 2) and motor aphasia. The Glasgow Coma Scale score was E4V3M6 on arrival. Diffusion-weighted magnetic resonance imaging (MRI) of the head showed a high-intensity zone in the left insular cortex and temporal lobe []. The left ICA and MCA were not clear []. The electrocardiogram showed sinus rhythm on arrival. Our neurologist started conservative therapy with heparin (10,000 U/day) and clopidogrel 75 mg/day. The symptoms of the patient improved on the day following admission; however, mild hemiparesis persisted (MMT = 4). The neurologist consulted us on day 6 about surgical treatment for the patient. Cervical and head computed tomography angiography (CTA) showed complete occlusion of the left CCA, extending from its origin to right before the carotid bifurcation. Riles type 1A occlusion was suspected. The left external carotid artery (ECA) was anastomosed with the left vertebral artery through a small branch of the occipital artery []. The anterior communicating artery was well developed, although there was a small unruptured aneurysm []. The left posterior communicating artery was hypoplastic []. The patient had undergone surgical treatment for a thoracic aortic aneurysm with vascular replacement 7 months before at another hospital. CTA also showed severe stenosis of the left subclavian artery and intermediate stenosis of the right brachiocephalic artery []. We suspected carotid artery occlusion at the anastomosed site of the synthetic vascular graft. We did not perform cerebral angiography for fear of catheter-induced synthetic graft injury of the anastomosed site. Single-photon emission computed tomography (SPECT) showed a general decrease in blood flow in the left cerebral hemisphere at rest []. Acetazolamide stress SPECT was not performed in the early phase of ischemic stroke as there was a risk of recurrent stroke. On day 16, the patient experienced a second stroke. Diffusion-weighted MRI revealed high-intensity areas on the left temporal and parietal lobes []. The patient presented with the right hemiparesis, motor aphasia, and Gerstmann syndrome. Argatroban hydrate (30 mg/day for 2 days followed by 10 mg/day for 5 days) and aspirin (200 mg/day) were administered. On day 17, her symptoms improved, except for the persistent mild hemiparesis (MMT = 4) and Gerstmann syndrome. Despite intensive medical care, the patient had a recurrent stroke. The collateral blood flow from the hypoplastic posterior communicating artery was not viable. Furthermore, collateral blood flow from posterior circulation through occipital artery anastomosis was not considered because of severe stenosis of the left brachiocephalic artery. Therefore, the development of collateral blood flow was not possible after long-term multiple antiplatelet therapies. Furthermore, we did not expect the risk of hyperperfusion to be so high, because the blood flow of the unilateral CCA is shared with the bilateral ICA. Hence, we decided to perform surgical vascular reconstruction in the acute phase of stroke. Due to severe stenosis of the left subclavian artery, left subclavian- or axillary-to-carotid bypass could not be performed. We consulted our endovascular surgeon regarding the risk of performing transcatheter angioplasty. There was a fear of catheter-induced suture injury of the aorta synthetic graft, which could be catastrophic if performed on this patient. Furthermore, we wished to avoid a complicated two-stage vascular reconstruction, which would involve subclavian to carotid bypass following subclavian angioplasty, to reduce invasiveness. Although we considered a bonnet bypass, the left STA was too thin to allow sufficient blood flow. In addition, the patient had unruptured aneurysms in the right MCA and anterior communicating artery. We avoided the bonnet bypass in case surgical clipping would be needed for aneurysms in the future. The right CCA with intermediate stenosis was the only choice for the donor site. The patient had a history of arteriosclerotic occlusion of the femoral artery and right subclavian artery and had undergone vascular reconstruction. We were not certain of the condition of the radial artery graft. Therefore, we decided to perform a carotid-to-carotid crossover bypass with a synthetic vascular graft. On day 25, vascular reconstructive surgery was performed. Dual antiplatelet therapy (aspirin 200 mg/day and clopidogrel 75 mg/day) was administered until 7 days before the surgery and continued with a single antiplatelet drug (aspirin 200 mg/day) until surgery. The patient was placed in a supine position under general anesthesia. The somatosensory evoked potential (SEP), motor evoked potential (MEP), and near-infrared spectroscope (NIRS) were monitored. First, the neck was rotated to the left side at approximately 30°. A linear skin incision along the sternocleidomastoid muscle (SCM) was made to expose the right CCA. After exposing 3 cm of the right CCA, we began the contralateral procedure. The neck was rotated to the right side at approximately 30°, and a linear skin incision was made along the left SCM. We then exposed the left CCA, ECA, and ICA. Indocyanine green showed a stump of an isolated CCA. The length of the stump was approximately 10 mm. Based on the length of the stump and the diameter of the CCA, we chose a 6 mm Gore-Tex® Stretch vascular graft and CV-7 Gore-Tex suture® (W.L. Gore and Associates, Inc., Medical Product Division, Flagstaff, AZ, USA). We created a subcutaneous tunnel with a shunt passer and passed it through a synthetic graft. Before clamping, edaravone 30 mg, methylprednisolone (125 mg), phenytoin (250 mg), and 20% mannitol (300 ml) were administered for cerebral protection. Heparin 4000 U was also infused. We then clamped the right CCA and made a linear vascular incision with a spits scalpel and dilated the arteriotomy with an aortic puncher. Since the orifice of the carotid artery was very small, the carotid shunt, which may have interrupted the back wall suture, was not used. We then performed right carotid artery-synthetic graft end-to-side anastomosis with a running suture []. Debris and air were flushed out through the synthetic graft. After completing the anastomosis, we clamped the synthetic graft and released the right CCA. The total clamp time of the right carotid artery was 21 min 52 s. After adjusting the length of the synthetic graft, we clamped the left ICA and ECA with a titanium aneurysm clip. In addition, we clamped the proximal end of the left CCA. We made a linear vascular incision with a spits scalpel, dilated the arteriotomy with an aortic puncher, and performed the synthetic graft-left CCA end-to-side anastomosis in the same way as were done for the right side []. Unlike in a typical carotid endarterectomy, we did not flush debris and air to the ECA due to fear of causing embolization. Therefore, we started anastomosis from the heel to the toe of the orifice on both the front and back wall using double-armed suture thread. Before ligating the back and front wall suture threads, we declapmed the external and internal carotid arteries to flush the debris and air through the toe of the vascular orifice [ and ]. After flushing the debris and air, we ligated the anastomosis and released the left ECA, ICA, and CCA. The total clamp time was 21 min and 38 s. After declamping, good pulsation of the synthetic graft was observed [ and ]. There was no remarkable change in SEP, MEP, and NIRS during surgery. The postoperative course of the patient was uneventful. No additional neurological symptoms were observed. Careful blood pressure control was performed to avoid hyperperfusion syndrome. Postoperative MRI showed no additional infarction. Head-and-neck CTA showed perfect patency of the crossover bypass []. The postoperative SPECT (postoperative day 14) did not show a remarkable improvement in cerebral blood flow []. The symptoms of the patient improved, but mild acalculia and alexia persisted. The patient had asymptomatic intermediate stenosis of the right proximal brachiocephalic artery; hence, we consulted a vascular interventional radiologist. Careful observation with single antiplatelet medication therapy (aspirin 100 mg/day) was recommended. The patient was discharged to a rehabilitation hospital. During the follow-up period at the outpatient clinic, the patient was able to independently perform daily activities, and cervical MRA showed perfect patency of the synthetic graft.