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MR perfusion imaging reveals regions of hypoperfusion associated with aphasia and neglect
A E Hillis1, P B Barker, N J Beauchamp
1Department of Neurology, Division of Cognitive Neurology, Johns Hopkins University Medical Institute, Baltimore, MD 21287, USA.
Objective:
To evaluate diffusion-weighted imaging (DWI) and MR perfusion imaging (MRPI) as tools for identifying regions of infarct and hypoperfusion associated with aphasia and neglect in hyperacute stroke. Secondary goal: to establish a functional correlate of a radiologically defined "ischemic penumbra."
Methods:
Forty subjects underwent DWI, MRPI, and standardized tests for lexical deficits or hemispatial neglect within 24 hours of stroke onset or progression. Ten patients had repeat DWI, MRPI, and cognitive testing after 3 days (in some cases after reperfusion therapy). Pearson correlations between error rate on cognitive testing and volume of abnormality on DWI versus MRPI were determined at each time period, and regions of hypoperfusion corresponding to specific cognitive deficits were identified.
Results:
Error rate was more strongly correlated with volume of hypoperfused tissue on MRPI (r = 0.65 to 0.93; p < 0.01 to p < 0.0003) than with volume of lesion on DWI (r = 0.54 to 0.75; p = 0.14 to p < 0.01) for dominant and nondominant hemisphere stroke, at each time point. Forty-eight percent of aphasic patients and 67% of those with hemispatial neglect had either no infarct or only small subcortical infarct on DWI, but had focal cortical hypoperfusion. Patients who had successful reperfusion therapy showed resolution of the hypoperfused territory beyond the infarction on repeat MRPI and showed resolution of corresponding deficits.
Conclusions:
MRPI shows regions of hypoperfused cortex associated with lexical deficits or hemispatial neglect, even when DWI shows no infarct or only small subcortical infarct. MRPI-DWI mismatch indicates regions of functionally salvageable tissue.
Insights
MR perfusion imaging (MRPI) better identifies stroke-related hypoperfusion and cognitive deficits than diffusion-weighted imaging (DWI). MRPI-DWI mismatch highlights salvageable brain tissue in acute stroke patients.
Area of Science:
- Neuroimaging
- Stroke research
- Cognitive neuroscience
Background:
- Hyperacute stroke management requires precise identification of ischemic tissue.
- Diffusion-weighted imaging (DWI) detects infarcts, but may miss early hypoperfusion.
- MR perfusion imaging (MRPI) assesses blood flow, offering complementary information.
Observation:
- Forty stroke patients underwent DWI, MRPI, and cognitive testing within 24 hours.
- Cognitive deficits (aphasia, neglect) were correlated with imaging findings.
- Repeat imaging and testing were performed after 3 days, including in patients receiving reperfusion therapy.
Findings:
- MRPI-derived hypoperfused volume showed a stronger correlation with cognitive deficit severity than DWI-derived infarct volume.
- Many patients with aphasia or neglect had hypoperfusion on MRPI without significant infarct on DWI.
- Successful reperfusion therapy correlated with resolution of hypoperfusion and cognitive deficits.
Implications:
- MRPI is crucial for detecting functionally significant hypoperfusion in hyperacute stroke.
- The MRPI-DWI mismatch identifies the ischemic penumbra, representing potentially salvageable brain tissue.
- These findings support MRPI's role in guiding acute stroke treatment decisions.