Hemispheric differences in ischemic stroke: is left-hemisphere stroke more common?
Vishnumurthy Shushrutha Hedna1, Aakash N Bodhit, Saeed Ansari
1Department of Neurology, University of Florida, Gainesville, FL, USA.
Insights
Left-hemisphere ischemic strokes are more common and associated with worse outcomes than right-hemisphere strokes. Large-vessel ischemic strokes, often due to atherosclerosis or cardioembolism, are more frequent in the left middle cerebral artery territory.
Area of Science:
- Neurology
- Vascular Neurology
- Stroke Medicine
Background:
- Understanding stroke mechanisms is crucial for developing effective therapies.
- Investigating hemispheric differences in ischemic stroke can reveal key mechanistic insights.
- Cerebral artery anatomy and blood flow dynamics may influence stroke laterality.
Purpose of the Study:
- To determine if left- and right-hemisphere ischemic strokes differ in frequency, severity, functional outcome, and mortality.
- To assess if large-vessel ischemia is more prevalent in the left middle cerebral artery territory due to circulatory factors.
Main Methods:
- Analysis of a combined dataset of 317 patients with ischemic stroke, excluding specific stroke types.
- Correlation of stroke laterality and vascular distribution with outcomes using logistic regression.
- Identification of large-vessel stroke etiologies as atherosclerosis and cardioembolism.
Main Results:
- Left-hemispheric strokes were more frequent (54%) and associated with higher admission NIHSS scores, increased mortality, and greater rates of mechanical thrombectomy.
- Ischemic strokes were more common in the left middle cerebral artery distribution, driven by a higher incidence of large-vessel ischemic stroke.
- Significant differences were observed in event frequency, mortality, stroke severity (NIHSS), and intervention rates between hemispheres.
Conclusions:
- Left-hemispheric ischemic strokes appear more frequent and often result in worse outcomes compared to right-hemispheric strokes.
- A higher incidence of large-vessel ischemic strokes in the left middle cerebral artery territory contributes to these observed hemispheric disparities.
- Excluding middle cerebral artery strokes diminishes the observed hemispheric differences, suggesting its significant role.
Background And Purpose:
Understanding the mechanisms underlying stroke can aid the development of therapies and improve the final outcome. The purposes of this study were to establish whether there are characteristic mechanistic differences in the frequency, severity, functional outcome, and mortality between left- and right-hemisphere ischemic stroke and, given the velocity differences in the carotid circulation and direct branching of the left common carotid artery from the aorta, whether large-vessel ischemia (including cardioembolism) is more common in the territory of the left middle cerebral artery.
Methods:
Trial cohorts were combined into a data set of 476 samples. Using Trial of Org 10172 in Acute Stroke Treatment criteria, ischemic strokes in a total 317 patients were included in the analysis. Hemorrhagic stroke, stroke of undetermined etiology, cryptogenic stroke, and bilateral ischemic strokes were excluded. Laterality and vascular distribution were correlated with outcomes using a logistic regression model. The etiologies of the large-vessel strokes were atherosclerosis and cardioembolism.
Results:
The overall event frequency, mortality, National Institutes of Health Stroke Scale (NIHSS) score, Glasgow Coma Scale score, and rate of mechanical thrombectomy interventions differed significantly between the hemispheres. Left-hemispheric strokes (54%) were more common than right-hemispheric strokes (46%; p=0.0073), and had higher admission NIHSS scores (p=0.011), increased mortality (p=0.0339), and higher endovascular intervention rates (p≤0.0001). ischemic strokes were more frequent in the distribution of the left middle cerebral artery (122 vs. 97; p=0.0003) due to the higher incidence of large-vessel ischemic stroke in this area (p=0.0011).
Conclusions:
Left-hemispheric ischemic strokes appear to be more frequent and often have a worse outcome than their right-hemispheric counterparts. The incidence of large-vessel ischemic strokes is higher in the left middle cerebral artery distribution, contributing to these hemispheric differences. The hemispheric differences exhibit a nonsignificant trend when strokes in the middle cerebral artery distribution are excluded from the analysis.
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