“We hope that, pending higher level evidence from a randomized controlled trial that we envision, patients with M2 occlusions presenting with disabling neurological deficits should be heavily considered for endovascular therapy and probably treated with the intervention to give them their best chances of better outcomes,” Dr. Sarraj added.

“The most important limitation of the study is that we do not know what made the physicians decide whether to treat a patient medically or with endovascular therapy,” writes Dr. Jonathan M. Coutinho from Academic Medical Center in Amsterdam in a related editorial. “As a result, we cannot exclude the possibility that residual confounding variables biased the results.”

“Although we must always be careful with the interpretation of results from nonrandomized studies, the data clearly suggest that it is at least reasonable to consider mechanical thrombectomy in these patients,” he adds. “Whether this consideration applies to all M2 occlusions remains to be seen.”

“Most likely, the decision to perform mechanical thrombectomy in a patient with an M2 occlusion will remain one that must be carefully weighed in each case,” Dr. Coutinho concluded. “However, that decision certainly has become a little easier with the data from this study.”

Dr. Gerhard Schroth from the University of Bern, Switzerland, who has published several studies of EVT for acute stroke, told Reuters Health by email, “M2 is a big artery and its occlusion should be treated by interventional neuroradiology.”

“If the clinical symptoms are severe (e.g., NIHSS more than 5), it should be treated by thrombectomy – what we call endovascular image-guided microsurgical thrombectomy – without any restriction,” he said. “The interventional neuroradiologist has to make a risk-benefit calculation, based on the vascular anatomy, which he investigates by DSA (Digital Subtraction Angiography).”

“The risk to perform an intervention may be too high, e.g., if the patient is agitated and moves the head (indicating intubation and general anesthesia) or if there is a severe arteriosclerotic process, e.g., with ipsilateral high-grade carotid stenosis,” Dr. Schroth said. “However – again – these are no absolute contraindications – our high-volume stroke center (more the 1,500 acute strokes, more than 200 thrombectomies per year) would aspirate or perform stent-retriever thrombectomy if the symptoms are severe.”