NIH Stroke Scale as a Predictor of Clot Presence, Location, and Persisting Occlusion in Candidates for Thrombolysis
Background: In acute stroke, few tools are readily available to determine clot presence and location before thrombolysis, nor whether occlusion persists after intravenous TPA. Because the NIH Stroke Scale (NIHSS) is easily obtained in the Emergency Department, we correlated sequential NIHSS scores and arterial occlusion in prospective candidates for IV TPA. Methods: Potential thrombolysis patients evaluated with transcranial Doppler (TCD) ultrasound and the NIHSS at the time of presentation were studied. TCD was performed using previously validated criteria for clot detection, localization, and subsequent degree of recanalization after thrombolysis. In patients treated at <180 minutes with conventional dose TPA (0.9 mg/kg), repeat NIHSS scores and diagnostic TCD were performed at the end of infusion. Results: 119 ischemic stroke patients met inclusion criteria (age 68±15, NIHSS 15±7, median 14, range 2–36), with 83% having occlusion consistent with symptoms. Occlusion was present in all patients with NIHSS ≥22, none with NIHSS <4, and there was a direct relationship between baseline NIHSS and clot presence (p<0.0001). Each additional NIHSS point increased the odds of occlusion by 1.33(95%CI 1.17–1.51). In patients with anterior circulation symptoms (N=80), increasing NIHSS corresponded with increasing M1 MCA and/or ICA occlusion, and decreasing vascular patency or M2 occlusion (p<0.001). In thrombolysed patients with initial vascular occlusion (N=55), end-of-infusion NIHSS was less predictive of persisting occlusion, with 70% of patients with scores ≥6 having persisting occlusion and 20% of patients with scores ≥16 having complete recanalization. The odds of persisting occlusion per end-of-infusion NIHSS point were 1.14 (95%CI 1.06–1.24,p <0.0008). Conclusions: Baseline NIHSS accurately predicts clot presence with increasing scores corresponding to increasing clot burden. However, NIHSS becomes less predictive of clot persistence at the end of TPA infusion and may less accurately identify patients for further revascularization efforts.