Endovascular therapy improved outcomes in mild large-vessel stroke with perfusion mismatch

Design

Multicentre, open-label, randomised trial (MILD-MT)

Population

300 patients in China with anterior LVO, NIHSS <6, small core and large perfusion mismatch, ≤24 h

Primary outcome

mRS 0–1 at 90 days

Effect

69.4% vs 50.0%; OR 2.32 (1.41–3.81); serious procedural complications 13.2%

Whether to thrombectomy patients with large-vessel occlusion but mild deficits has been one of the open questions in stroke care. MILD-MT, an open-label multicentre trial in China published in NEJM on 23 October, randomised 304 patients with anterior-circulation large-vessel occlusion, NIHSS under 6, a small infarct core and a large perfusion mismatch, within 24 hours of onset or last known well. Patients received endovascular therapy plus medical management, or medical management alone.

At 90 days, 69.4% of the endovascular group had an excellent outcome (mRS 0–1) against 50.0% with medical management (OR 2.32, 95% CI 1.41–3.81). Symptomatic intracranial haemorrhage occurred in three patients in each group. However, serious procedure-related complications occurred in 19 patients (13.2%), and the one death was in the endovascular group.

The selection matters: patients needed perfusion imaging showing substantial salvageable tissue, so the result does not apply to all mild strokes with an occlusion. Outcome assessment in an open-label trial is a possible source of bias, and the case for thrombectomy in mild strokes without this imaging selection remains unsettled. Guidelines have not yet changed. In India, perfusion imaging and thrombectomy are concentrated in larger centres, which shapes who could be selected this way.

• In mild stroke with a proximal anterior-circulation occlusion, consider perfusion imaging to identify salvageable tissue.
• Discuss patients with a small core and large mismatch with a thrombectomy centre, even when NIHSS is under 6.
• Weigh the 13% rate of serious procedural complications with the patient and family before intervening.
• Do not extend this result to mild strokes without perfusion mismatch or to posterior-circulation occlusions.

Why it matters

It suggests a low NIHSS should not exclude thrombectomy when imaging shows a lot of tissue still at risk.

Don't overread it

One open-label trial in selected patients with perfusion mismatch; guidelines have not changed and the result does not cover all mild strokes.

The statistics, in plain English

An odds ratio of 2.32 means about twice the odds of an excellent outcome; in absolute terms, about 19 more patients in every 100 reached mRS 0–1. The confidence interval (1.41–3.81) excludes 1.0, so chance alone is unlikely.

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