Sustained Benefit of Endovascular Therapy in Acute Ischemic Stroke

Endovascular thrombectomy for large vessel intracranial occlusion has been established beyond doubt as standard of care in select patients with acute ischemic stroke.1 Several sentinel randomized trials were published in 2015 and were responsible for demonstrating the benefit of endovascular mechanical thrombectomy in improving outcomes as measured by modified Rankin scores (mRS) and reducing mortality.2 These studies examined mRS scores at 90 d postintervention and found positive results with mechanical thrombectomy. While this conveyed short-term advantage for the properly selected endovascular stroke patient, sustained benefit has not been well documented in controlled trials. The investigators for the MR CLEAN study3 adopted an extended study design beyond the original study in which they sought to follow enrolled patients for 2 yr. The primary outcome was mRS at 2 yr and secondary outcomes were mortality and quality of life (QOL). Of the 500 patients in the original study, 391 patients had 2-yr outcome data. One hundred ninety-four were in the intervention group and 197 in the “conventional” group (who did not undergo endovascular therapy). The results of the study indicated that endovascularly treated patients had statistically better odds (ratio of 1.68 and P = .007) of favorable mRS outcome at 2 yr. They also had higher QOL scores (P = .006).1 It should be noted that the study highlights some nuances that challenge a simplistic interpretation of commonly applied assessment scales. Lower rates of mRS 0 or 1 were seen at 2 yr in comparison to 90-d scores in the original study. The interpretation was that challenges with daily activities tend to be magnified outside of rehab settings, that are typical of patients studied early in their poststroke course. This implies that the administration and documentation of mRS scores is subject to vagaries and is not infallible. Better stroke outcome measures are necessary in the broader sense of stroke trials. Interestingly, subgroup analyses according to NIHSS (National Institutes of Health Stroke Scale) score, age, occlusion of the internal carotid artery terminus, additional extracranial internal carotid artery obstruction, time from stroke onset to randomization and the Alberta Stroke Program Early CT score did not show any relation to intervention. This may not be consistent with routine clinical experience. A plausible explanation would be the inconsistency of measurement and quantification of ischemic penumbra tissue and the need for robust, user-friendly techniques to achieve the same. The rate of major vascular events in either treatment arm was surprisingly low and likely does not reflect average community practice. This potentially hints at continual risk factor modification and this cannot be emphasized enough. Also of interest is that the study showed some difference in mortality rates in favor of endovascular therapy that did not reach significance, while death rates were similar between the 2 groups in the original study. In summary, the evidence that endovascular thrombectomy leads to improved outcomes, both short and medium term, is convincing. Extending the beneficiary pool to patients outside the conventional time window is being investigated4 and is the next exciting step in endovascular neurosurgical stroke management. Sophisticated yet accessible and rapid penumbral imaging will increasingly become the decision-making step. Accelerated device development to improve recanalization rates in patients with challenging anatomy is also a step in the right direction. All of this needs to be coupled with improvements in emergency medical and triage systems, critical care management, risk factor management, and application of deep learning methods to stroke databases. Neurosurgery is uniquely positioned to spearhead these and other innovations in stroke care and thus help tackle an important public health problem.

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