NIH Stroke Scale Calculator
Score stroke severity using the NIH Stroke Scale 15-item neurological assessment. Get instant severity classification and treatment recommendations.
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Formula
NIHSS Total = Sum of all 15 item scores (Range: 0-42)
Each of the 15 items is scored on an ordinal scale. Items include level of consciousness (3 sub-items), best gaze, visual fields, facial palsy, motor arm (left and right), motor leg (left and right), limb ataxia, sensory, best language, dysarthria, and extinction/inattention.
Worked Examples
Example 1: Moderate Acute Ischemic Stroke
Problem:A 68-year-old patient presents with right-sided weakness, slurred speech, and mild facial droop 2 hours after symptom onset. Score: LOC=0, Questions=1, Commands=0, Gaze=0, Visual=0, Facial=1, Left Arm=0, Right Arm=3, Left Leg=0, Right Leg=3, Ataxia=0, Sensory=1, Language=1, Dysarthria=1, Extinction=0.
Solution:Total NIHSS = 0+1+0+0+0+1+0+3+0+3+0+1+1+1+0 = 11 Severity: Moderate Stroke (5-15) Motor subscore: 0+3+0+3 = 6 (right-sided weakness) Cognitive subscore: 0+1+0+1 = 2 (mild language/LOC deficit)
Result:NIHSS Score: 11 (Moderate) - Strong candidate for IV tPA within 4.5-hour window
Example 2: Severe Left MCA Stroke
Problem:A 72-year-old presents with global aphasia, right hemiplegia, and forced eye deviation. Score: LOC=1, Questions=2, Commands=2, Gaze=2, Visual=2, Facial=3, Left Arm=0, Right Arm=4, Left Leg=0, Right Leg=4, Ataxia=0, Sensory=2, Language=3, Dysarthria=2, Extinction=2.
Solution:Total NIHSS = 1+2+2+2+2+3+0+4+0+4+0+2+3+2+2 = 29 Severity: Very Severe Stroke (>25) Motor subscore: 0+4+0+4 = 8 (complete right hemiplegia) Cognitive subscore: 1+2+2+3 = 8 (severe cognitive impairment)
Result:NIHSS Score: 29 (Very Severe) - Emergency intervention, ICU admission, consider endovascular therapy
Frequently Asked Questions
What is the NIH Stroke Scale and how is it used clinically?
The NIH Stroke Scale (NIHSS) is a standardized 15-item neurological examination tool used by healthcare providers to assess the severity of an acute ischemic stroke. Developed by the National Institutes of Health, it quantifies neurological deficits across multiple domains including level of consciousness, eye movements, visual fields, facial symmetry, motor strength, sensation, coordination, speech, and language comprehension. The scale ranges from 0 to 42, with higher scores indicating more severe neurological impairment. It is the most widely used stroke assessment tool in emergency departments worldwide and guides critical treatment decisions including eligibility for thrombolytic therapy.
How do NIHSS scores correlate with stroke outcomes and treatment decisions?
NIHSS scores directly influence treatment pathways and predict clinical outcomes. Scores of 0 to 4 indicate minor stroke with generally favorable prognosis and high likelihood of functional independence. Scores of 5 to 15 represent moderate strokes where intravenous tPA (alteplase) within 4.5 hours provides the greatest benefit. Scores above 15 indicate severe strokes with higher mortality risk, where endovascular thrombectomy may be considered alongside IV tPA for large vessel occlusions. Research shows that each one-point increase in baseline NIHSS score increases the odds of poor outcome by approximately 17 percent. Serial NIHSS measurements also track recovery or deterioration over time.
What are the individual components assessed in the NIHSS examination?
The NIHSS evaluates 15 specific neurological functions: 1a) Level of consciousness (alertness), 1b) LOC questions (month and age), 1c) LOC commands (open/close eyes, grip/release), 2) Best gaze (horizontal eye movements), 3) Visual fields, 4) Facial palsy, 5a) Motor arm left, 5b) Motor arm right, 6a) Motor leg left, 6b) Motor leg right, 7) Limb ataxia (coordination), 8) Sensory (pain/touch), 9) Best language (aphasia assessment), 10) Dysarthria (speech clarity), and 11) Extinction and inattention (neglect). Each item is scored on an ordinal scale with varying maximum points, together producing the composite score.
When should the NIHSS be administered and who can perform it?
The NIHSS should be administered as soon as possible upon presentation of suspected stroke symptoms, ideally within the first minutes of emergency department arrival. It is typically performed by emergency physicians, neurologists, stroke nurses, and paramedics who have completed NIHSS certification training. The assessment takes approximately 6 to 10 minutes for trained examiners. It should be repeated at regular intervals including 2 hours post-treatment, 24 hours, at discharge, and at follow-up visits to track neurological changes. The National Stroke Association recommends that all stroke center personnel maintain current NIHSS certification through accredited training programs.
What are the limitations and potential pitfalls of the NIHSS scoring system?
While the NIHSS is an invaluable clinical tool, it has notable limitations that clinicians must understand. The scale has a hemispheric bias, weighting left hemisphere functions (language) more heavily than right hemisphere functions (spatial neglect), meaning right hemisphere strokes may receive lower scores despite significant disability. Posterior circulation strokes affecting the brainstem and cerebellum are often underscored because vertigo, cranial nerve deficits, and truncal ataxia are not well captured. The scale also cannot distinguish between acute deficits and pre-existing conditions, and scores may fluctuate based on patient cooperation, sedation, and examiner variability despite standardization efforts.
Why do left hemisphere strokes often score higher on the NIHSS than right hemisphere strokes?
The scale devotes substantial weight to language: the best language item and the dysarthria item both test functions that are usually left-lateralised, and several other items depend on the patient understanding commands. Right hemisphere syndromes express themselves mainly through neglect and extinction, which the scale captures in a single low-scoring item. The consequence is that a right hemisphere infarct of similar volume can produce a markedly lower total, so a low NIHSS on the right side should never be read as a small or unimportant stroke.
How is the NIHSS handled when an item cannot be tested?
The scale has explicit conventions rather than allowing items to be skipped. Limb ataxia is recorded as absent when the limb is plegic or the patient cannot cooperate, because ataxia cannot be demonstrated in a limb that will not move. Dysarthria may be marked untestable in an intubated or orally obstructed patient, and an amputated or fused limb is recorded as untestable rather than scored as weak. Because the rules differ item by item, a total from an incompletely testable examination is not directly comparable with a fully scored one.
What does a change in the NIHSS over serial examinations tell you?
The scale is designed for repetition, and the trajectory carries more information than any single total. A rising score after treatment prompts urgent reassessment for haemorrhagic transformation, worsening cerebral oedema, re-occlusion of a recanalised vessel, or a systemic cause such as hypoglycaemia, hypoxia or fever. A falling score suggests reperfusion or a recovering ischaemic penumbra. Because the scoring is ordinal rather than linear, a two-point move at the top of the range does not mean the same thing clinically as a two-point move near zero.
What is the difference between the NIHSS and the modified Rankin Scale?
They measure different things at different times. The NIHSS is an impairment scale scored at the bedside from a structured neurological examination, and it describes what the nervous system can currently do. The modified Rankin Scale is a global disability outcome measure, usually assessed weeks to months later, describing how much help a person needs in daily life. A high acute NIHSS raises the probability of a poor Rankin outcome but does not determine it, since recovery depends on lesion location, reperfusion and rehabilitation.
How are the motor arm and motor leg items scored?
Each limb is tested separately, so there are four motor scores in total. The arm is held extended with the palm down at ninety degrees when sitting or forty-five degrees when supine and observed for ten seconds; the leg is held at thirty degrees supine and observed for five seconds. Scoring runs from no drift, through drift that does not reach the bed, to some effort against gravity, then no effort against gravity, and finally no movement at all. Both sides are scored even when only one is obviously affected.
References
Background & Theory
History
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist · Editorial policy
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