What is the National Institutes of Health Stroke Scale (NIHSS) scoring system for stroke?

NIH Stroke Scale (NIHSS) Scoring System

The NIHSS is a standardized 11-item neurological examination scale ranging from 0 to 42 points, where higher scores indicate more severe neurological deficits, with scores >16 predicting high probability of death or severe disability and scores <6 predicting good recovery. 1, 2

Scale Components and Structure

The NIHSS assesses the following domains through 11 core items (though often expanded to include additional assessments): 3

• Level of consciousness - Evaluates alertness, orientation to month and age, and ability to follow commands 1
• Visual fields - Tests for hemianopia or visual field defects 3
• Gaze - Assesses horizontal eye movements and gaze deviation 3
• Facial palsy - Examines symmetry of facial movements 3
• Motor arm function (bilateral) - Each arm scored separately from 0-4 based on drift and movement against gravity 1, 4
• Motor leg function (bilateral) - Each leg scored separately similar to arms 5
• Limb ataxia - Tests coordination 6
• Sensory - Assesses sensation to pinprick 3
• Language - Evaluates fluency, comprehension, and naming ability 1
• Dysarthria - Tests articulation 3
• Extinction/inattention - Assesses for neglect 3

Detailed Motor Scoring Criteria

For motor arm and leg assessments, the specific scoring is: 4

• 0 points = No drift (limb holds position at 90° for full 10 seconds)
• 1 point = Drift (limb holds 90° but drifts down before 10 seconds)
• 2 points = Some effort against gravity (cannot maintain 90° but has some antigravity movement)
• 3 points = No effort against gravity (limb falls immediately)
• 4 points = No movement at all
• X = Unable to assess due to amputation, fusion, or fracture

Administration Requirements

All professionals involved in stroke care must be trained and certified in NIHSS administration by watching training videos and passing a standardized examination. 1, 2

• The scale takes only 5-10 minutes to administer and requires no historical information 2
• Assessment is based solely on direct examination findings 2
• The scale demonstrates high inter-rater reliability when administered by certified examiners 2

Timing of Assessment

The NIHSS must be performed at three critical timepoints: 2

• At presentation/hospital admission or within the first 24 hours
• At acute care discharge
• Upon transfer to rehabilitation if previous scores are unavailable

Prognostic Interpretation

The total score provides critical prognostic information: 1, 2

• Score <6 = Predicts good recovery
• Score >16 = Forecasts high probability of death or severe disability
• Score >20 = Indicates large stroke with poor prognosis 4

Clinical Applications

The NIHSS directly guides acute stroke management decisions: 2

• Determines eligibility for thrombolytic therapy 3, 2
• Tracks neurological deterioration or improvement during hospitalization 7
• A 4-point improvement or worsening may alter treatment eligibility 3
• Percent change from baseline to 3 months strongly predicts functional outcomes 7

Important Limitations and Caveats

• The NIHSS was designed primarily for anterior circulation strokes and may underestimate posterior circulation stroke severity because symptoms like vertigo and dysphagia are not included 3
• Distal motor function and balance/gait disorders are not adequately covered by the standard scale 3
• Two items (facial palsy and dysarthria) have demonstrated lower inter-rater reliability compared to other components 3, 6
• When assessing motor function, carefully distinguish between "no effort against gravity" (score 3) versus "no movement at all" (score 4) 4