Interventional Radiology · Neurointervention · Primary publication

DAWN: Thrombectomy 6–24 Hours After Stroke

DAWN established the benefit of mechanical thrombectomy 6–24 hours after last known well in highly selected patients with anterior-circulation large-vessel occlusion and clinical-core mismatch.

Key takeaway

In carefully selected patients with intracranial ICA or proximal M1 occlusion and a severe neurological deficit disproportionate to a small infarct core, thrombectomy 6–24 hours after last known well substantially improved 90-day functional outcomes.

At a glance

Study design: Multicentre, prospective, randomised, open-label controlled trial with blinded 90-day outcome assessment and a Bayesian adaptive-enrichment design; enrolment was stopped early after a prespecified interim analysis demonstrated efficacy.
Population: Adults with intracranial ICA or proximal M1 middle cerebral artery occlusion, last known well 6–24 hours earlier, baseline NIHSS of at least 10, prestroke modified Rankin Scale 0–1 and an age-adjusted clinical-core mismatch assessed using CT perfusion or diffusion-weighted MRI.
Sample size: 206 participants
Intervention: Trevo stent-retriever mechanical thrombectomy plus standard medical care.
Comparator: Standard medical care alone without mechanical thrombectomy or another intra-arterial treatment.
Primary endpoint: Two co-primary efficacy endpoints at 90 days: mean disability score on the utility-weighted modified Rankin Scale and functional independence, defined as modified Rankin Scale 0–2.

Key results

Mean utility-weighted modified Rankin Scale score at 90 days was 5.5 with thrombectomy versus 3.4 with control; adjusted difference 2.0 points, 95% credible interval 1.1–3.0, with posterior probability of superiority greater than 0.999.
Functional independence at 90 days occurred in 49% with thrombectomy versus 13% with control; adjusted difference 33 percentage points, 95% credible interval 24–44, with posterior probability of superiority greater than 0.999.
Symptomatic intracranial haemorrhage occurred in 6% with thrombectomy versus 3% with control; P=0.50.
Mortality at 90 days was 19% with thrombectomy versus 18% with control; P=1.00.

Limitations

The population was highly selected using strict age, NIHSS, infarct-core and occlusion criteria, limiting generalisability beyond the DAWN eligibility profile.
Treatment allocation was open-label, although 90-day outcome assessment was blinded.
The trial was stopped early for efficacy, which may overestimate the magnitude of treatment benefit.
The study was industry funded and evaluated a Trevo-based thrombectomy strategy at experienced stroke centres.

Why it matters

DAWN shifted late-window stroke selection from time alone towards clinical-core mismatch, establishing that appropriately selected patients with anterior-circulation large-vessel occlusion can benefit from thrombectomy up to 24 hours after last known well.

Practice implication

Patients with intracranial ICA or proximal M1 occlusion presenting 6–24 hours after last known well should not be excluded solely because of time; eligible patients require urgent vascular and infarct-core imaging to assess for DAWN-type clinical-core mismatch.

Exam pearl

Remember DAWN as a clinical-core mismatch trial: 6–24 hours, intracranial ICA or proximal M1 occlusion, NIHSS of at least 10, prestroke mRS 0–1 and a small age-adjusted infarct core.

Viva questions

What was the principal finding of the DAWN trial?: In selected patients with intracranial ICA or proximal M1 occlusion and clinical-core mismatch, thrombectomy 6–24 hours after last known well improved 90-day disability and functional independence compared with standard medical care alone.
What was the design of the DAWN trial?: It was a multicentre, prospective, randomised, open-label controlled trial with blinded outcome assessment and a Bayesian adaptive-enrichment design.
Which occlusion sites and treatment window were studied in DAWN?: The trial studied intracranial internal carotid artery or proximal M1 middle cerebral artery occlusion treated 6–24 hours after the patient was last known well.
What were the DAWN clinical-core mismatch thresholds?: For patients aged 80 years or older, NIHSS was at least 10 with core volume below 21 mL. For patients younger than 80 years, NIHSS was at least 10 with core below 31 mL, or NIHSS was at least 20 with core from 31 mL to below 51 mL.
What were the co-primary efficacy endpoints in DAWN?: The co-primary endpoints were mean utility-weighted modified Rankin Scale score and functional independence, defined as mRS 0–2, both assessed at 90 days.
What were the main efficacy results of DAWN?: Mean utility-weighted mRS was 5.5 versus 3.4, and functional independence was 49% versus 13%, both favouring thrombectomy.
Did thrombectomy significantly increase symptomatic intracranial haemorrhage or mortality in DAWN?: No. Symptomatic intracranial haemorrhage was 6% versus 3%, and 90-day mortality was 19% versus 18%; neither difference was statistically significant.
What is the major pitfall when interpreting DAWN?: DAWN did not establish thrombectomy for every stroke presenting within 24 hours. Benefit was demonstrated only in a highly selected population with intracranial ICA or proximal M1 occlusion and strict age-adjusted clinical-core mismatch criteria.