Background
Treatment of the symptomatic internal carotid artery (ICA) occlusion with contralateral ICA severe stenosis is a challenging neurological condition. Contralateral carotid artery stenting may be a possible decision in order to improve perfusion in the occluded ICA territory, in case of repetitive ischemic symptoms despite adequate collateral flow via extracranial carotid artery (ECA). However, improved cerebral flow through the revascularized ICA may cause unexpected adverse events. We present the patient with recurred stroke due to improved flow, confirmed by transcranial color-coded doppler ultrasonography (TCCD), related with distal embolization after carotid artery stenting.

Case Report
A 67-year-old male presented following several episodes of transient right leg weakness and involuntary trembling movement lasting only a few minutes. The patient had no known history of vascular risk factors. The neurological examination revealed facial paralysis and hypesthesia on the right side. Cerebral MRI demonstrated multiple acute diffusion restriction lesions in the left middle cerebral artery (MCA) and anterior cerebral artery (ACA) territory, consistent with multiple ischemic lesions mainly of embolic origin, bun an internal borderzone infarction was also considered. Contrast enhanced MR angiography revealed the occlusion of the left ICA, severe stenosis (>70%) of the right ICA, and nonvisualization of bilateral ACA. Sensory symptom and limb shaking movement in his right leg persisted even after admission and hydration. To improve perfusion of the left ICA territory via pial collaterals, carotid artery stenting in the right side was performed. Just after carotid artery stenting, angiography showed no additional collateral flow via pial arteries or anterior communicating artery. One day after the procedure, he presented confusion and right leg weaknes (MRC grade 4) and diffusion weighted MRI revealed newly developed ischemic lesions in the bilateral ACA (mainly in the left side) and the left MCA territory. On TCCD examination, approaching flow in the left ACA was visualized via anterior communicating artery.

Conclusion
Asymptomatic carotid artery stenting in order to improve perfusion of the contralateral occluded ICA territory should be performed with consideration of the possibility of distal embolization through revascularized ICA. TCCD may be the useful tool to assess the cerebral flow after carotid artery stenting.