Diffusion-perfusion mismatch: an opportunity for improvement in cortical function

Area of Science:

• Neuroimaging
• Stroke Medicine
• Cognitive Neurology

Background:

• Diffusion-perfusion mismatch is debated as a biomarker for the ischemic penumbra.
• Regions of mismatch not progressing to infarct are termed 'benign oligemia'.
• Hypoperfused tissue may remain dysfunctional and recoverable even without immediate infarct progression, especially in large vessel stenosis.

Purpose of the Study:

• To test the hypothesis that persistent diffusion-perfusion mismatch, defined by a hypoperfusion threshold of 4-5.9s delay on time-to-peak (TTP) maps, is associated with persistent cognitive deficits.
• To investigate if reperfusion of hypoperfused tissue influences cognitive recovery.

Main Methods:

• 38 patients with acute ischemic stroke underwent cognitive tests and MRI (diffusion and perfusion) within 24 hours of onset and again at 10 days.
• Most patients had large vessel stenosis or occlusion.
• Cognitive tests included naming or line cancellation.

Main Results:

• A persistent perfusion deficit (4-5.9s TTP delay) on follow-up MRI correlated with persistent cognitive deficits (p < 0.001).
• In patients without infarct growth (n=14), persistent hypoperfusion was linked to a lack of cognitive improvement compared to those with reperfusion.
• Changes in hypoperfused tissue volume (4-5.9s TTP delay) and diffusion-weighted imaging ischemic tissue volume were independently associated with cognitive function changes (p=0.002 and p=0.02, respectively).

Conclusions:

• Non-infarcted tissue with a TTP delay of 4-5.9s may be associated with persistent cognitive deficits, even if infarct progression is not imminent.
• This hypoperfused tissue may represent an opportunity for intervention to improve function days after stroke onset.