Watershed infarctions are more prone than other cortical infarcts to cause early-onset seizures.

Background Early-onset seizures(ESs) have been reported in 2% to 6% of strokes. Most previous studies have been retrospective and did not systematically perform cerebral magnetic resonance imaging (MRI). Objective To determine the prevalence and determinants of ESs in a prospective cohort. Design Prospective cohort study. Setting Stroke unit in an academic hospital. Patients Six hundred sixty-one consecutive individuals admitted to our stroke unit during an 18-month period for suspected stroke. Main Outcome Measures Initial investigations systematically included cerebral MRI. Among patients with MRI-confirmed cerebral infarction, individuals with ES, defined as occurring within 14 days of stroke, were identified. Results Three hundred twenty-eight patients had MRI-confirmed cerebral infarcts and 178 had cortical involvement. The ESs, all initially partial seizures, occurred in 14 patients (4.3%) and at stroke onset in 5 patients. The ESs occurred exclusively in patients with cortical involvement ( P P  = .007). Logistic regression analysis showed an almost 4-fold increased risk of ES in patients with watershed infarctions compared with other cortical infarcts (odds ratio, 4.7; 95% confidence interval, 1.5- 15.4; P  = .01). Age, sex, diabetes mellitus, hypertension, smoking, National Institutes of Health Stroke Scale score, and cardioembolic origin were not significant risk factors for ES. Conclusions The cortical hemispheric location of ischemic strokes is associated with a higher risk of ES. Among these patients, the watershed mechanism is a strong and independent determinant of stroke-related ES.