The NIHSS Score and its Components can Predict Cortical Stroke

Neuroprotective agents have the potential to reduce ischemia to penumbra of the cortex, but are time-sensitive. To quickly determine whether a cortical stroke is present without imaging, we created a scoring system based on the NIH stroke scale (NIHSS) that can accurately predict cortical damage in an acute ischemic stroke (AIS).

Patients treated with tPA for AIS were retrospectively assessed through prospectively acquired databases at two stroke centers. Stroke was classified as cortical vs. non-cortical stroke. The total NIHSS score, cortical components (gaze, visual fields, language, and neglect) and cortical score (sum of cortical components) were analyzed for site 1 and then validated for site 2 for sensitivity and positive predictive value (PPV) for a cortical stroke.

An acute infarct was detected in 194/239 (81%) patients at site 1 and 122/174 (70%) at site 2 on diffusion-weighted MRI. Cortical involvement was found in 71% (site 1) and 75% (site 2). The median cortical score was 25% of the total NIHSS score at both sites. NIHSS ≥ 4 had the highest sensitivity; PPV was 90% for any cortical sign with ≥ 2 points. The best combination of sensitivity and PPV was cortical score/NIHSS score ≥10%.

If a trial targeting cortical stroke required that the cortical score represent at least 10% of the total NIHSS score with no imaging, less than 10% of patients with cortical stroke would be missed and less than 18% of patients would be misclassified as having a cortical stroke.