The NIH Stroke Scale Has Limited Utility in Accurate Daily Monitoring of Neurologic Status

Abstract

Background and purpose: The National Institute of Health Stroke Scale (NIHSS) is rapid and reproducible, a seemingly attractive metric for the documentation of clinical progress in patients presenting with ischemic stroke. Many institutions have adopted it into daily clinical practice. Unfortunately, the scale may not adequately capture all forms of functional change. We evaluate its utility as a measure of recovery in patients treated with intravenous tissue plasminogen activator (IV tPA) for ischemic stroke.

Methods: We prospectively evaluated the difference in the rate of improvement based on NIHSS (a ≥4 point change based on previous trials) versus physician-documented subjective and objective measures in 41 patients' status post IV tPA treatment. The NIHSS 24 hours posttreatment, on discharge, and at follow-up were compared to NIHSS on admission using tests of proportions and McNemar tests of paired data. Secondary analyses were performed defining significant improvement as NIHSS changes of 1 to 3 points.

Results: The mean NIHSS improved from 9 to 6, 24 hours post-tPA. Of the 41 patients, 29 improved by physician documentation, although only 11 of the 29 met the NIHSS criteria (P < .001; McNemar P < .001). On discharge, 20 of the 41 patients met the NIHSS criteria; however, the proportion "better" by physician documentation (71%) remained significantly higher (P = .04; McNemar P = .004). The mean postdischarge follow-up NIHSS was 2. Twenty of the 21 patients improved by documentation versus 16 of the 21 by NIHSS (P = .08, McNemar P = .125). Using NIHSS changes of 1 to 3 increased sensitivity for detecting improvement but remained lower than physician documentation.

Conclusion: The NIHSS has many advantages; however, it may miss functional changes when used in place of a comprehensive neurological examination to measure improvement poststroke.

Keywords: outcomes; recovery; stroke; tissue plasminogen activator (tPA).

Conflict of interest statement

Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.

The National Institute of Health Stroke Scale (NIHSS) fails to capture a significant percentage of patients with physician-documented improvement after intravenous tissue plasminogen activator (IV tPA).