Lesion patterns and mechanism of ischemia in internal carotid artery disease: a diffusion-weighted imaging study.

CONTEXT Although embolism and low-flow phenomenon are the 2 main mechanisms of stroke in internal carotid artery (ICA) occlusive disease, the mechanism of border-zone infarction remains controversial. Diffusion-weighted imaging (DWI) can more easily detect small or multiple ischemic lesions than conventional imaging. OBJECTIVES To investigate the ischemic lesion patterns on DWI and to discuss the mechanisms of stroke in ICA disease. DESIGN Case series. SETTING A tertiary referral center. PATIENTS We enrolled 35 consecutive patients who had an acute ischemic stroke and (> or = 70%) stenosis or an occlusion of the extracranial ICA confirmed by cerebral angiography and an acute relevant stroke lesion on DWI within 1 week of onset, but without cardiac sources of embolism and tandem intracranial arterial disease. MAIN OUTCOME MEASURES The lesion pattern on DWI was categorized as territorial or border zone. Multiple ischemic lesions were defined as noncontiguous lesions on DWI in more than 1 vascular territory. RESULTS There were 3 distinctive stroke lesion patterns. (1) A territorial lesion without a border-zone lesion was found in 21 patients: superficial and superficial territorial in 9, superficial and deep territorial in 7, and single in 5. (2) A border-zone lesion with or without a territorial lesion was found in 10 patients: border zone and territorial in 9 and border zone alone in 1. (3) Bilateral hemispheric lesions were found in 4 patients. Multiple ischemic lesions were found in 29 (82.9%) of the 35 patients. No patient had episodes of hemodynamic compromise. CONCLUSIONS An acute ischemic lesion in ICA occlusive disease is mainly multiple. Border-zone infarction was mostly associated with territorial infarction. These results support the fact that embolism is the predominant stroke mechanism in ICA occlusive disease.