Nih Stroke Scale Score

NIH Stroke Scale Score: Predicting Stroke Outcomes and Applications

Baseline NIH Stroke Scale Score and Stroke Outcomes

The National Institutes of Health Stroke Scale (NIHSS) is a critical tool for assessing the severity of stroke and predicting patient outcomes. Research has consistently shown that the baseline NIHSS score is a strong predictor of recovery after an ischemic stroke. For instance, a study involving 1,281 patients found that each additional point on the NIHSS decreased the likelihood of excellent outcomes at 7 days by 24% and at 3 months by 17%. Patients with lower NIHSS scores (≤6) had a higher probability of good recovery, while those with scores ≥16 faced a high probability of death or severe disability.

Retrospective NIHSS Scoring Reliability

Retrospective assessment of the NIHSS score from medical records has been validated for its reliability and accuracy. Studies have shown that retrospective NIHSS scoring using an algorithm based on written history and physical admission notes is reliable, with high interrater reliability (r²=0.98) and excellent agreement with prospective scores (r²=0.94). This method allows for accurate stroke severity adjustment in retrospective research, even when some physical examination data are missing .

NIHSS in Anterior vs. Posterior Circulation Strokes

The NIHSS may not fully capture the spectrum of neurologic deficits in posterior circulation (PC) strokes compared to anterior circulation (AC) strokes. Research indicates that the baseline NIHSS score is generally lower in PC strokes, and specific subscores such as ataxia and visual fields are higher. The optimal cutoff scores for predicting favorable outcomes were found to be ≤5 for PC strokes and ≤8 for AC strokes, highlighting the need for tailored assessment criteria for different stroke types.

Expanded NIHSS for Posterior Circulation Strokes

To address the limitations of the NIHSS in evaluating posterior circulation strokes, an expanded version (e-NIHSS) has been developed. This version includes additional items to better assess signs and symptoms specific to PC strokes. Studies have shown that the e-NIHSS provides a more accurate assessment, with patients scoring an average of 2 points higher on the e-NIHSS compared to the traditional NIHSS, indicating improved sensitivity for PC strokes.

Early Stroke Recognition and Prehospital Assessment

The NIHSS has also been adapted for early stroke recognition and prehospital use. An abbreviated version, known as the Out-of-hospital NIH Stroke Scale, includes key items such as facial palsy, motor arm, and dysarthria, achieving a sensitivity of 100% and specificity of 88% for stroke identification. Additionally, a shortened NIHSS for emergency medical services (sNIHSS-EMS) has been developed to facilitate rapid and comprehensive prehospital stroke assessment, including stroke recognition, severity grading, and prediction of large vessel occlusion (LVO).

Conclusion

The NIH Stroke Scale is a vital tool in stroke assessment, with strong predictive value for patient outcomes. Its reliability in both prospective and retrospective settings, along with adaptations for specific stroke types and prehospital use, underscores its importance in clinical practice and research. Continued refinement and validation of the NIHSS and its variants will enhance stroke care and improve patient outcomes.

Summary

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