Middle cerebral artery infarcts encompassing the insula are more prone to growth
Hakan Ay1, E Murat Arsava, Walter J Koroshetz
1Department of Neurology, A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA. hay@partners.org
Background And Purpose:
Based on previous observations that infarcts encompassing the insula were linked to unfavorable clinical outcome, we hypothesized that insular damage was directly associated with worsened infarction in ischemic but potentially viable neighboring brain tissue.
Methods:
Using acute diffusion- and perfusion-weighted MRI within the first 12 hours of symptom onset and a follow-up MRI on day 5 or later, we calculated the percentage of mismatch lost (PML) in 61 consecutive patients with ischemic stroke within the middle cerebral artery territory. PML denoted the percentage of mismatch tissue between diffusion-weighted imaging and mean transit time maps that eventually underwent infarction. We explored the relationship between PML and insular location using a regression model.
Results:
The median PML was 17.7% (interquartile range, 3.5% to 54.2%) in insular and 2.5% (0.0% to 12.7%) in noninsular infarcts (P<0.01). The PML correlated with the volume of abnormal regions on diffusion-weighted imaging (P<0.01), mean transit time (P<0.01), cerebral blood flow maps (P<0.01), and cerebral blood volume maps (P<0.01). A linear regression model with PML as response and with acute MRI volumes, age, and the site of vascular occlusion as covariates showed that insular involvement was an independent predictor of PML (P=0.01). The regression model predicted an approximately 3.2-fold increase in PML with insular involvement.
Conclusions:
Infarction of the insula is associated with increased conversion of ischemic but potentially viable neighboring tissues into infarction. The unfavorable tissue outcome in insular infarcts may not be a mere bystander effect from proximal middle cerebral artery occlusions.
Insights
Insular damage in stroke patients significantly increases the risk of converting ischemic brain tissue into infarction. This finding highlights the insula's critical role in stroke outcomes.
Area of Science:
- Neurology
- Neuroradiology
- Stroke Medicine
Background:
- Previous studies link insular infarcts to poor clinical outcomes.
- The insula's role in the progression of ischemic stroke requires further investigation.
Purpose of the Study:
- To investigate the association between insular damage and the expansion of infarction in surrounding ischemic brain tissue.
- To determine if insular involvement independently predicts the conversion of potentially viable tissue into infarct.
Main Methods:
- Utilized diffusion- and perfusion-weighted MRI within 12 hours of stroke onset in 61 patients.
- Calculated the percentage of mismatch lost (PML) to quantify tissue conversion.
- Employed regression modeling to assess the relationship between insular location and PML.
Main Results:
- Patients with insular infarcts showed a significantly higher median PML (17.7%) compared to non-insular infarcts (2.5%).
- Insular involvement was an independent predictor of PML, predicting a 3.2-fold increase.
- PML correlated significantly with various acute MRI parameters including diffusion-weighted imaging volumes and perfusion maps.
Conclusions:
- Infarction of the insula is directly associated with increased conversion of ischemic tissue to infarct.
- This suggests insular infarcts contribute to unfavorable tissue outcomes beyond proximal artery occlusions.
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