The National Institutes of Health Stroke Scale (NIHSS) is a systematic assessment tool that provides a quantitative measure of stroke-related neurologic deficit. The NIHSS was originally designed as a research tool to measure baseline data on patients in acute stroke clinical trials. Now, the scale is also widely used as a clinical assessment tool to evaluate acuity of stroke patients, determine appropriate treatment, and predict patient outcome.
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| NIH Stroke Scale |
The NIHSS can be used as a clinical stroke assessment tool to evaluate and document neurological status in acute stroke patients. The stroke scale is valid for predicting lesion size and can serve as a measure of stroke severity. The NIHSS has been shown to be a predictor of both short and long term outcome of stroke patients. Additionally, the stroke scale serves as a data collection tool for planning patient care and provides a common language for information exchanges among healthcare providers.
The scale is designed to be a simple, valid, and reliable tool that can be administered at the bedside consistently by physicians, nurses or therapists.
Intended Population
Individuals with Stroke
Method of Use
The NIHSS is a 15-item neurologic examination stroke scale used to evaluate the effect of acute cerebral infarction on the levels of consciousness, language, neglect, visual-field loss, extraocular movement, motor strength, ataxia, dysarthria, and sensory loss. A trained observer rates the patent’s ability to answer questions and perform activities. Ratings for each item are scored on a 3- to 5-point scale, with 0 as normal, and there is an allowance for untestable items. Scores range from 0 to 42, with higher scores indicating greater severity. A single patient assessment requires less than 10 minutes to complete.
The evaluation of stroke severity depends upon the ability of the observer to accurately and consistently assess the patient. Stroke severity may be stratified on the basis of NIHSS scores as follows:
- Very Severe: >25
- Severe: 15 – 24
- Mild to Moderately Severe: 5 – 14
- Mild: 1 – 5
Reliability
Inter-rater reliability for individual elements of the NIHSS has been shown to be generally good. However overall scoring can be inconsistent, proper training is required to use the NIH Stroke Scale accurately.
- A study of 4 patients assessed by 30 physicians and 29 study coordinators, with a space of 3 months between assessments, found that the NIHSS has excellent interrater (ICC = 0.95) and test-retest reliability (ICC = 0.93)
- A study of 20 patients rated by 4 clinicians, with each patient subsequently evaluated by 2 independent observers found Adequate to Excellent interrater agreement for 9 of the 13 items on the NIHSS (Kappa = 0.32 to 0.79); lowest levels of agreement were found for the Facial palsy (Kappa = 0.22) and limb ataxia (Kappa = -0.16) items.
- 4 items have poorly reliability or are redundant (level of consciousness, facial weakness, ataxia, and dysarthria
Validity
Outcomes related to NIHSS scores at admission:
- Scores of <5; 80% of stroke survivors will be discharged to home
- Score between 6 and 13 typically require acute inpatient rehabilitation
- Scores of >14 frequently require long-term skilled care
Responsiveness
NIHSS scores were compared to infarction size (measured by computed tomography) on 65 patients at 1 week post stroke. 10 items demonstrated an average of 25% change over 7 days. However, changes in limb ataxia and best gaze may have been overstated.
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