Intra-procedural SSEP latency stratifies functional outcome after successful endovascular thrombectomy

BACKGROUND: Successful angiographic reperfusion during endovascular thrombectomy (EVT) does not reliably predict 90-day functional recovery. Whether intra-procedural somatosensory evoked potential (SSEP) latency dynamics stratify outcome among patients achieving successful recanalization remains unevaluated. METHODS: In this exploratory sub-study nested within the prospective COMPETE trial, consecutive anterior large-vessel occlusion patients with modified Thrombolysis in Cerebral Infarction (mTICI) ≥2b underwent intra-procedural SSEP monitoring. Three sequential Classification and Regression Tree analyses used N20-derived variables (primary; n=84), P40-derived variables (secondary; n=71), and combined N20/P40 variables (tertiary; n=56). Bootstrap resampling (n=1000) assessed variable selection stability. Favorable outcome was modified Rankin Scale (mRS) 0-2 at 90 days. RESULTS: Across all three analyses, latency variables consistently outranked amplitude. In the primary analysis, Max ΔN20 Latency was the dominant root discriminator (bootstrap selection ~90%; cut-off 2.25 ms, 95% CI 0.85 to 4.65 ms; Area Under the Receiver Operating Characteristic Curve (AUC-ROC) 0.746, 95% CI 0.644 to 0.848), with favorable outcome rising from 26% to 77% across terminal classes (P<0.001). In the secondary analysis, Max P40 Latency was the strongest discriminator (bootstrap selection ~93%; cut-off 49 ms, 95% CI 47.40 to 54.70 ms; AUC 0.887, 95% CI 0.814 to 0.959), stratifying favorable outcome as 90% vs 35% (P<0.001). In the tertiary combined analysis, Max P40 Latency was the primary split and Max ΔN20 Latency the secondary; favorable outcome ranged from 27% to 93% (P<0.001). CONCLUSION: Among patients achieving successful angiographic reperfusion, intra-procedural SSEP latency dynamics were associated with stratified 90-day functional outcome with bootstrap-supported reproducibility. These findings suggest that intra-procedural SSEP latency may serve as a candidate real-time physiologic indicator during EVT, warranting prospective external validation.