Sequential Contralateral Large-Vessel Occlusion Following Intravenous Thrombolysis: A Case Report of Dynamic Bilateral Cerebral Arterial Thrombosis.

Acute large-vessel occlusion stroke can evolve rapidly during the hyperacute treatment period, occasionally resulting in a clinical and radiological picture that differs substantially from the initial presentation. We report an unusual case of sequential contralateral large-vessel occlusion occurring within approximately three hours. A patient presented with transient dysphasia that resolved rapidly. While awaiting stroke assessment, he developed confusion, left-sided weakness, and dysarthria. Initial imaging demonstrated a distal right middle cerebral artery (MCA) occlusion with a National Institutes of Health Stroke Scale (NIHSS) score of 6. CT angiography (CTA) demonstrated extensive occlusion of the left internal carotid artery (ICA) from its origin through the petrous and intracranial segments; however, the left MCA remained patent. Intravenous thrombolysis was administered, and the patient was transferred for mechanical thrombectomy of the right MCA occlusion. During transfer, he developed sudden complete aphasia and clinical features of a left total anterior circulation syndrome, with deterioration in NIHSS score to 20. Repeat CTA demonstrated recanalisation of the previously occluded right MCA but a new complete occlusion of the previously patent left MCA. The patient underwent emergency left MCA thrombectomy with excellent reperfusion. Neurological recovery was rapid, with an NIHSS score of 2 at 24 hours. The temporal and radiological sequence raised the possibility of distal embolisation or propagation of thrombus from the pre-existing left ICA occlusion following intravenous thrombolysis; however, causality could not be definitively established. Further investigation demonstrated severe left ventricular systolic dysfunction due to non-ischemic dilated cardiomyopathy without definite intraventricular thrombus. Anticoagulation was subsequently commenced. This case is notable for the sequential development of major occlusions in opposite cerebral hemispheres, with documented recanalisation of the initial symptomatic vessel concurrent with emergence of a new dominant-hemisphere occlusion. It highlights the importance of repeated neurological assessment and a low threshold for repeat vascular imaging when the neurological phenotype changes after intravenous thrombolysis. Rapid recognition of a new large-vessel occlusion can permit timely thrombectomy and potentially prevent severe permanent neurological disability.