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Reperfusion by endovascular therapy doesn't just rescue ischemic brain tissue in stroke patients -- it is also associated with lower odds of fluid accumulation in the brain, according to a secondary analysis of the MR CLEAN trial.

Measured as midline shift in follow-up imaging, brain edema was less likely when patients got successful reperfusion (mTICI score 2b or 3, P<0.001) and recanalization (modified arterial occlusive lesion score 3, P<0.001). A longer time to reperfusion was tied to edema (P<0.001) and each 90-minute delay associated with a 0.80 mm midline shift (P=0.001).

Any midline shift was associated with worse functional outcome at 90 days (modified Rankin score >2, P<0.001): , according to W. Taylor Kimberly, MD, of Massachusetts General Hospital in Boston, and colleagues.

"Moreover, we demonstrated that worse functional outcome associated with unsuccessful blood flow restoration, lower ASPECTS, or later reperfusion could be explained partially by brain edema formation as measured by midline shift," the authors wrote in JAMA Neurology. The study also was presented at the International Stroke Conference in Los Angeles.

"Taken together, our data provide insight into the association between reperfusion and brain edema. Our study reinforces the benefits of early reperfusion and recanalization in reducing brain edema and suggests that endovascular therapy does not increase the extension of brain edema, as has been reported in preclinical models," according to Kimberly's group. "These data also suggest that edema may help explain the previous observation that final infarct volume only partially accounts for the endovascular therapy effect on outcome."

The present MR CLEAN analysis included 462 patients with acute anterior circulation ischemic stroke who were randomized to intraarterial therapy or usual therapy.

Midline shift was numerically more common in conventional therapy than stent retriever therapy arm without reaching statistical significance (58.8% versus 41.2%, P=0.27).

Kimberly's group acknowledged that midline shift is an indirect measure for water concentration. "Approximately half of patients did not have measurable midline shift but may have had a small amount of edema that did not lead to a change in the midline shift measurement," they noted.

Another caveat is the study's exclusion of patients with parenchymal hemorrhage types 1 and 2, even though patients commonly have these hemorrhages and edema at the same time.

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