Background and purpose: The National Institutes of Health Stroke Scale (NIHSS) score is known to be effective in predicting the likelihood of recovery after stroke. However, the baseline NIHSS score predicts long-term outcomes rather crudely because early changes in stroke scores may influence the stroke outcomes. Therefore, a precise prognostic algorithm or a cutoff point for predicting long-term outcomes based on data from serial NIHSS scores is needed.
Methods: We serially assessed 437 patients with acute symptomatic ischemic stroke within the middle cerebral artery territory who presented with nonlacunar stroke and were followed-up for at least 6 months after symptom onset. The NIHSS score was serially checked at 0, 1, 3, 7, and 14 days after admission. In all patients, the Barthel index (BI) and the modified Rankin Scale (mRS) score were checked, with a poor outcome defined as any of the following endpoints: death, modified mRS score of >3, or BI of <60.
Results: A marked neurological improvement or worsening (i.e., a change in the NIHSS score of at least 4) was seen in 13.5% or 5.5% of the patients, respectively, during the first 7 days after admission. About 25% of the 437 patients had poor long-term outcomes. Analysis of receiver operating characteristic curves showed that the NIHSS score at day 7 after admission was better for predicting poor long-term outcomes than was the baseline score (P=0.003). In addition, we analyzed the cutoff point of the 7th-day NIHSS score for predicting a poor outcome at 6 months after symptom onset. An NIHSS score of at least 6 at day 7 after admission predicted poor long-term outcomes with a sensitivity of 84% [95% confidence interval (CI), 76-90%], a specificity of 92% (95% CI, 88-94%), and positive and negative predictive values of 77% and 95%, respectively. A logistic regression analysis revealed that age, diffusion-weighted imaging lesion volume, stroke history, and 7th-day NIHSS score were independently associated with poor outcome. However, no score used in addition to the 7th-day NIHSS score improved the prediction of a poor outcome.
Conclusions: An NIHSS score of at least 6 on day 7 after admission accurately forecasts a poor long-term outcome after stroke. Our data may be helpful in predicting the long-term prognosis as well as in making decisions regarding novel therapeutic applications in subacute-stroke trials.
Keywords: Ischemic stroke; Outcome; Stroke scale.