Internal and cortical border-zone infarction: clinical and diffusion-weighted imaging features

The pathogenesis of internal border-zone (IBZ) and cortical border-zone (CBZ) infarcts is unclear. Both types of infarct have been combined into a single group in most previous reports, which has produced conflicting results. We hypothesized that different pathogenic mechanisms underlie IBZ and CBZ infarcts.

We reviewed 946 consecutive patients with ischemic stroke within the middle cerebral artery territory. IBZ and CBZ infarcts were selected based on diffusion-weighted imaging templates to identify vascular territories. Baseline patient characteristics, clinical courses, and neuroradiological features were compared between patients with IBZ and CBZ infarcts.

We identified 45 IBZ and 75 CBZ infarct patients. Compared with the CBZ infarct patients, IBZ infarct patients had a higher degree of stenosis or occlusion in either the middle cerebral or internal carotid artery (P=0.008) and exhibited a rosary-like pattern of infarction more frequently (P<0.001). In contrast, concomitant small cortical infarcts were observed more frequently in CBZ infarct patients (P<0.001). Clinical deterioration during the first 7 days of admission and poor outcome after 3 months after stroke was more prevalent in IBZ infarct patients than in CBZ infarct patients (P=0.002 and P=0.003, respectively).

IBZ infarcts are caused mainly by hemodynamic compromise, whereas embolic pathogenesis appears to contribute greatly to the genesis of CBZ infarcts. Patients with IBZ infarcts showed poor early and late clinical courses. Our findings suggest that different therapeutic approaches may be required to prevent early clinical deterioration in patients with different types of border-zone infarcts.