Role of the NIH Stroke Scale in Stroke Assessment and Management

Key Components and Administration

The NIH Stroke Scale is a standardized, validated instrument specifically designed to assess the severity of neurological impairment after stroke, with scores ranging from 0 to 42, and is recommended by the American Heart Association for use in all stroke patients at presentation, within 24 hours of admission, and at discharge to guide treatment decisions and predict outcomes 1, 2, 3, 4
The scale consists of 11 original items, takes only 5-10 minutes to administer, and is based solely on examination, requiring no historical information or contributions from surrogates, allowing for objective assessment 2, 3
An additional item examining finger extension is often added to the NIHSS to assess distal upper extremity weakness, which is more common than proximal arm weakness in stroke patients 1, 2
The scale can be administered by any trained clinician who has been properly certified 2, 3

The NIHSS should be performed at three critical timepoints: at the time of presentation/hospital admission or within the first 24 hours, at the time of acute care discharge, and upon transfer to rehabilitation if previous scores are not available 1, 2, 3, 4
The scale is particularly valuable in guiding decisions about acute stroke therapy, including the use of thrombolytic therapy, and has high inter-rater reliability between examiners, making it highly reproducible across different healthcare settings 2, 3

The NIHSS strongly predicts patient outcomes after stroke, with a score greater than 16 forecasting a high probability of death or severe disability, and a score less than 6 forecasting a good recovery 1, 2, 3
During the first week after acute ischemic stroke, the NIHSS can identify patients likely to have poor outcomes 2

All professionals involved in any aspect of stroke care should be trained and certified to assess stroke severity using the NIHSS, which is achieved by watching a training videotape and passing an examination that involves scoring patients shown on a test tape 2, 3, 4
Ongoing validation of the predictive value of the NIHSS through prospective data collection is encouraged to maintain and improve its clinical utility 2, 3

When assessing motor function, it's essential to distinguish between no effort against gravity and no movement at all 5
For language assessment, even subtle hesitations or circumlocutions may indicate mild aphasia rather than normal language function 6

The American Heart Association recommends using the National Institutes of Health Stroke Scale (NIHSS) to quantify neurological impairment after stroke, with higher scores indicating more severe deficits, and serves as a guide for acute treatment decisions, including thrombolytic therapy eligibility, although the NIHSS significantly underestimates posterior circulation stroke severity because symptoms like vertigo, dysphagia, and ataxia are not included in the assessment 7

The NIHSS has a systematic underestimation of posterior circulation stroke severity, and posterior circulation patients evaluated with expanded NIHSS versions score an average of 2 points higher than with classical NIHSS, indicating that thrombolytic treatment should not be withheld based solely on low NIHSS scores, with 71% of posterior circulation stroke patients presenting with NIHSS ≤4, yet 15% of these "minor" strokes result in poor outcomes at 3 months 7

The NIHSS is a 42‑point, 11‑item neurological examination that can be completed in 5–10 minutes and serves as the primary tool for determining eligibility for thrombolytic therapy and for predicting patient outcomes. 8
Developed by the National Institutes of Health for use in clinical stroke trials, the scale has been extensively validated to reduce inter‑observer error. 9
Higher NIHSS scores reflect more severe neurological deficits; the scale is designed so that virtually any stroke will register at least one abnormality. 8
The examination relies exclusively on objective findings and does not require historical information or input from family members. 8
An optional finger‑extension item is often added to assess distal upper‑extremity weakness, but this item is not included in the total score. 8

The screening NIHSS must be performed by an examiner experienced in acute stroke care who has achieved certification in administering the scale. 9
A baseline NIHSS establishes initial stroke severity; a change of ±4 points from baseline may alter a patient’s eligibility for thrombolytic therapy and requires reassessment before proceeding. (Evidence cited in the source)
If the NIHSS improves by ≥4 points or crosses predefined thresholds before cerebral angiography, the patient may become ineligible for randomization in treatment protocols. 9
Admission NIHSS scores are used to determine eligibility for thrombolytic therapy and to guide all acute‑stroke treatment decisions. 8

An NIHSS score > 16 predicts a high probability of death or severe disability, whereas a score < 6 predicts a good recovery. 8
Initial NIHSS scores are strongly correlated with outcomes in retrospective analyses of randomized clinical trials. 8
Within the first week after an acute ischemic stroke, the NIHSS can identify patients who are highly likely to experience poor outcomes. 8

NIHSS assessments are mandatory at three timepoints: (1) at presentation or within the first 24 hours of hospital admission, (2) immediately before any therapeutic intervention, and (3) at acute‑care discharge. 8
A second assessment performed just before diagnostic cerebral angiography serves as a re‑check, often yielding a more accurate score because the patient is stabilized and can cooperate better. 8
If a patient is transferred to rehabilitation without documented NIHSS scores, the rehabilitation team should complete an NIHSS assessment. 8

All professionals involved in stroke care must be trained and certified to assess stroke severity using the NIHSS by viewing a training video and passing a competency examination. 8
Certification ensures accurate severity assessment and reduces inter‑observer variability. 8

The NIHSS significantly underestimates the severity of posterior‑circulation strokes because it does not include symptoms such as vertigo, dysphagia, and ataxia. 9
The scale was originally designed primarily for evaluation of anterior‑circulation ischemic strokes. 9