Safety and Efficacy of MCA‐M2 Thrombectomy in Delayed Time Window: A Propensity Score Analysis From the STAR Registry
Bibliographic record
Abstract
Background Mechanical thrombectomy of middle cerebral artery M2 segment occlusion of the middle cerebral artery has reported safety and efficacy in recent post‐hoc and observational studies. However, there is no known benefit of mechanical thrombectomy for patients with M2 segment occlusions in the delayed time window (>6 hours). Methods The Stroke Thrombectomy and Aneurysm Registry (STAR) is a prospective, multicenter, nonrandomized observational study registry for acute ischemic stroke thrombectomy and aneurysm treatment. We analyzed all patients who underwent mechanical thrombectomy within the late time window (>6 hours from symptom onset) involving isolated M2 occlusions. We used propensity score matching to select a comparison group of patients who underwent mechanical thrombectomy for M1 occlusion in the same time window. Results Of 1083 consecutive patients analyzed, propensity matching yielded 180 well matched M1 and M2 pairs. Baseline demographics were well balanced between the groups (M1 and M2). Alberta stroke program early CT score (7.6±1.7 versus 8.3±1.5; P <0.001) was higher in the M2 group. There was a trend towards less complete recanalization (Thrombolysis in Cerebral Infarction 3) 46.1% versus 39.9% ( P =0.053) in the middle cerebral artery M2 segment cohort. However, successful recanalization (Thrombolysis in Cerebral Infarction 2b‐3) was better in middle cerebral artery M2 segment cohort (85% versus 90.5%; P =0.053). Postprocedural asymptomatic hemorrhage rates were similar (29.4% versus 27.8%; P =0.816), but symptomatic hemorrhage rates were higher in the M1 group (7.2% versus 2.2%; P =0.047). Rates of good clinical outcome (modified Rankin scale 0–2) were similar at final follow‐up (43.9% versus 46.7%; P =0.672). The overall mortality was also similar between the cohorts (12.8% versus 13.9%; P =0.877). Conclusion In our analysis of the Stroke Thrombectomy and Aneurysm Registry, M2 occlusions not only achieved similar rates of recanalization and good functional outcome compared with M1 occlusions in a delayed time window (6–24 hours from last normal) but also had less symptomatic intracranial hemorrhage.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".