Mark McAllister, MD
Hakimelahi R, Vachha B, Copen W, Papini G, He J, Higzai M, et al. Time and Diffusion Lesion Size in Major Anterior Circulation Ischemic Strokes. Stroke. 2014
“Time is brain” has been a vigorously repeated motto among vascular neurologists since the early 1990s. When evaluating acute strokes we emphasize urgency, lest more brain undergoes irreversible damage. The primary reason patients don’t receive therapy for acute ischemic stroke is presentation outside of the established time windows for intervention. In this paper the authors investigate the relationship between time from symptom onset and infarct size in patients with anterior circulation occlusions.
The study included both retrospectively (47) and prospectively identified (139) acute stroke patients who had CTA or MRA evidence of occlusion at the terminal ICA, proximal MCA, or T-lesion with and DWI performed within 30 hours of symptom onset. The group calculated DWI infarct volumes for each of the patients, and found that there was no correlation between infarct volume and time from symptom onset (R²=0.001, p=0.71). When analyzed by occlusion location (ICA, MCA, or both), there remained no correlation, which was also true when considering only patients with witnessed symptom onset.
The authors conclude that time is not the most important determinant of infarct size. Variability in collaterals among patients likely plays a significant role, which is dramatically demonstrated in radiographs from two patients in the included figures. This paper does not evaluate changes in infarct size within individual patients, but previous work by the same group has suggested perfusion deficits may be stable in an individual.
The authors suggest that the individuals with low DWI burdens and good collaterals may be potential candidates for intervention beyond currently established windows, consistent with other cited reports of positive outcomes in such circumstances. What remains to be seen is whether such patients are at risk of infarct expansion and thus would benefit from intervention, or whether these patients are destined to do well regardless of our actions.
i think one day, we will look back at the use of time windows as if we were living in the dark ages. we base our decisions on time as it is the quickest, most cost-effective, widely accessible mode of stratifying patients. newer technologies like perfusion scanning have proven imperfect thus far. as any experienced practitioner working with stroke patients knows, the decision for acute intervention is highly dependent on collaterals. hopefully further research will capitilize on this underappreciated aspect of acute stroke evaluation.