A case of carotid web with rapid thrombus expansion following mechanical thrombectomy with pathological evaluation by carotid endarterectomy.

A 48-year-old man with no history of diagnosis with any abnormality was admitted to our hospital 43 min after onset of stroke. He had a right conjugate deviation and severe left hemiparesis, and his initial National Institutes of Health Stroke Scale (NIHSS) score was 13. Computed tomography (CT) of the head revealed no early ischemic changes, while CT angiography showed occlusion of the M1 proximal segment of the right middle cerebral artery. Intravenous thrombolysis was administered within 27 min of admission, and mechanical thrombectomy was performed. Effective reperfusion was achieved 55 min after puncture. Carotid web (CaW) at the root of the right internal carotid artery was suspected to be the source of the embolus. Carotid ultrasonography (CUS) on the following day revealed an oval-shaped structure of equal intensity rising from the far wall. The structure enlarged over time, despite the administration of an antiplatelet agent. In addition to thrombi, intramural hematoma and neoplastic lesions were considered in the differential diagnosis. Carotid endarterectomy was performed on day 6. Pathologically, a mixed thrombus was identified adhering to the CaW; however, no neoplastic changes were observed. There were no postoperative complications, and the patient was discharged without neurological deficits on day 14. The CaW has anatomical factors morphologically associated with a high risk of thrombus formation. Pathologically, the involvement of hydrodynamic factors was considered more significant than the influence of the CaW surface morphology. CUS is a useful tool for assessing thrombus morphology.