Are there time-dependent differences in diffusion and perfusion within the first 6 hours after stroke onset?

Area of Science:

• Neurology
• Radiology
• Emergency Medicine

Background:

• Stroke heterogeneity on CT scans may explain the limited efficacy of intravenous tissue plasminogen activator (tPA) therapy within 3-6 hours.
• Multiparametric MRI can investigate early, time-dependent differences in acute stroke pathophysiology.

Purpose of the Study:

• To investigate early time-dependent differences in acute ischemic stroke pathophysiology using multiparametric MRI.
• To assess if stroke characteristics differ significantly between <3 hours and 3-6 hours post-stroke onset.

Main Methods:

• 112 acute ischemic stroke patients within 6 hours of symptom onset underwent MRI.
• Patients were dichotomized into <3-hour and 3-6 hour groups.
• Lesion volumes (ADC_man, ADC <550, TTP delay) and infarct volumes (days 5-8) were analyzed, with subsamples for MCA occlusions and tPA treatment.

Main Results:

• No significant differences in apparent diffusion coefficient (ADC) and time-to-peak (TTP) lesion volumes were found between the <3-hour and 3-6 hour groups.
• In tPA-treated patients, no significant differences in ADC_man, TTP >2 seconds, or infarct volume were observed between the groups.
• While some differences in diffusion-perfusion mismatch and TTP delay were noted in specific subgroups (MCA trunk/branch occlusions), they did not reach statistical significance after multiple testing correction.

Conclusions:

• No significant time-dependent differences in diffusion or perfusion impairment were observed within 6 hours post-stroke onset.
• Excluding patients from intravenous tPA solely based on a rigid 3-hour window appears unjustified in MRI-confirmed ischemic stroke.