Perfusion-diffusion mismatch on MRI in stroke evaluation indicates what about brain tissue?

Perfusion-diffusion mismatch on MRI in stroke evaluation indicates what about brain tissue?

• A. Fully infarcted tissue with no salvageable potential.
• B. Normal brain tissue unaffected by stroke.
• C. Tissue at risk (penumbra) with relatively preserved diffusion signal.
• D. Areas with decreased diffusion and reduced perfusion consistent with core infarct.

Answer: (C)

In acute ischemic stroke, diffusion and perfusion MRI tell us different things about tissue status. Diffusion-weighted imaging highlights areas of cytotoxic edema that occur early in irreversible injury, so regions with restricted diffusion are typically the infarct core. Perfusion imaging shows current blood flow; when a region has reduced perfusion but the diffusion signal is still preserved, that area is at risk but not yet permanently damaged. This mismatch—where perfusion is impaired but diffusion remains relatively normal—defines the penumbra: tissue that is ischemic and vulnerable yet potentially salvageable with timely reperfusion. That’s why the best answer describes tissue at risk (penumbra) with relatively preserved diffusion signal. If both diffusion is restricted and perfusion is reduced, that region is more likely the core infarct. If there’s neither diffusion restriction nor perfusion deficit, that tissue is normal. And if diffusion is restricted but perfusion is not severely reduced, that pattern isn’t the typical mismatch scenario and isn’t the salvageable tissue we’re trying to identify.

In acute ischemic stroke, diffusion and perfusion MRI tell us different things about tissue status. Diffusion-weighted imaging highlights areas of cytotoxic edema that occur early in irreversible injury, so regions with restricted diffusion are typically the infarct core. Perfusion imaging shows current blood flow; when a region has reduced perfusion but the diffusion signal is still preserved, that area is at risk but not yet permanently damaged.

This mismatch—where perfusion is impaired but diffusion remains relatively normal—defines the penumbra: tissue that is ischemic and vulnerable yet potentially salvageable with timely reperfusion. That’s why the best answer describes tissue at risk (penumbra) with relatively preserved diffusion signal.

If both diffusion is restricted and perfusion is reduced, that region is more likely the core infarct. If there’s neither diffusion restriction nor perfusion deficit, that tissue is normal. And if diffusion is restricted but perfusion is not severely reduced, that pattern isn’t the typical mismatch scenario and isn’t the salvageable tissue we’re trying to identify.