Published Online
on July 22, 2004

A more recent version of this article appeared on September 1, 2004

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Submitted on February 19, 2004
Revised on May 20, 2004
Accepted on June 21, 2004

Are There Time-Dependent Differences in Diffusion and Perfusion Within the First 6 Hours After Stroke Onset?

Jens Fiehler MD^*; Thomas Kucinski MD; Karina Knudsen MSt; Michael Rosenkranz MD; Götz Thomalla MD; Cornelius Weiller MD; Joachim Röther MD; and Hermann Zeumer MD

From the Departments of Neuroradiology (J.F., T.K., K.K., H.Z.) and Neurology (M.R., G.T., C.W., J.R.), University Hospital Eppendorf, University of Hamburg, Germany.

^* To whom correspondence should be addressed. E-mail: fiehler{at}uke.uni-hamburg.de.

Background and Purpose--Stroke heterogeneity in computed tomography-based studies has been attributed as main cause for missing efficacy of intravenous tissue plasminogen activator (tPA) therapy within 3 to 6 hours. We investigated early time-dependent differences in acute stroke pathophysiology by multiparametric magnetic resonance imaging (MRI).

Methods--Stroke MRI of 112 acute ischemic stroke patients within <6 hours were dichotomized into a <3-hour group (n=52) and a 3- to 6-hour group (n=60). Infarct volume was determined on days 5 to 8. Lesion volumes were determined for apparent diffusion coefficient (ADC_man) and the subregion with ADC values <550x10^-9 mm/s² (ADC <550), and for the time-to-peak (TTP) delay of 2 to 4 seconds, 4 to 6 seconds, 6 to 8 seconds, and >8 seconds. A subsample analysis was performed for occlusions of the middle carotid artery (MCA) trunk (n=36) and MCA branches (n=30), and for all patients treated by intravenous tPA (n=70).

Results--ADC and TTP lesion volumes were not different within <3 hours compared with volumes at 3 to 6 hours. In patients receiving intravenous tPA (n=70), there were no significant differences in ADC_man, TTP >2 seconds, and infarct volume (days 5 to 8) between the 2 groups. There was a greater proportion of ADC <550/ADC_man, which was most pronounced in patients with MCA trunk occlusions after 3 to 6 hours and a larger mismatch in the <3-hour group compared with that of the 3- to 6-hour group. In MCA branch occlusions, there was a less severe TTP delay after 3 to 6 hours. However, all differences missed the significance level (P=0.05) after correction for multiple testing.

Conclusions--We observed no significant time-dependent differences within 6 hours after stroke onset in degree and volume of diffusion and perfusion impairment. An exclusion from intravenous tPA solely based on a rigid 3-hour time window seems unjustified in MRI-confirmed ischemic stroke.

Key words: ischemia • magnetic resonance imaging • magnetic resonance imaging, diffusion-weighted • stroke, acute • thrombolysis

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