Abstract
INTRODUCTION: PROMISE trial has shown high predictive accuracy of the N20 somatosensory evoked potential (SEP) response on functional recovery in patients with AIS undergoing endovascular thrombectomy (EVT). This secondary study aims to describe the association between the N20 response and imaging biomarkers of ischemic penumbra, infarct volume and collateral flow. METHODS: Presence and amplitude of the N20 response was recorded before EVT. At baseline, infarct core was automatically calculated establishing a threshold value of ADC<620x10‐6mm2/s in MR and of rCBF<30% in CTP; ischemic volume was estimated as Tmax >6 sec; and hypoperfusion intensity ratio (HIR) as the proportion of ischemic volume that also has a delay in Tmax>10s. Leptomeningeal collaterals were classified according to the Arterial Collateral Grading Scale in CTA as "poor" (absence and <50%) and optimal (>50%, equal to and greater than the contralateral), or according to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology scale when the acquired image was dynamic MR angiography, dichotomized as incomplete collateral fill (poor collateral) (grades 0 to 2) and complete collateral fill (optimal collateral) (grades 3 and 4). Collaterals were not evaluated in the conventional angiography since we did not perform a full study to shorten the time to thrombus access. The adjusted predictive value of N20 for functional recovery was analyzed by logistic regression and compared with imaging variables by using receiver operating characteristic curves. RESULTS: From 223 patients studied, 99 patients had multimodal imaging with perfusion studies and N20 assessable recordings at baseline (mean age, 70y; median NIHSS, 18), 63 patients with present (N20+) and 36 with absent N20 response (N20‐). Median infarct core was 12 (0‐25) and 16 (3‐60) cc (p= 0,193), ischemic volume 81 (39‐132) and 111 (54‐188) cc (p=0,082) and the HIR 0,4 (0,2‐0,6) 0,4 (0,3‐0,6) (p=0,572), respectively. N20+ was associated to a better collateral flow (OR 2,5; [1,2‐5,3]; p=0,01). N20+ showed the highest predictive capacity of functional recovery at day 7 compared to imaging variables (Table 1) and increased 15 (4‐103) fold the likelihood of good outcome after adjusting for collateral flow 2.94 (1.10‐8.40), ASPECT score (1,17 (0,74 ‐ 1,87) and infarct core 0.98 (0.95‐1.01). CONCLUSION: N20 SEP response is a powerful biomarker of functional recovery that might surrogate advanced imaging in patients with AIS evaluated for endovascular thrombectomy.