Printed on 3/17/2026
For informational purposes only. This is not medical advice.
The National Institutes of Health Stroke Scale (NIHSS) is a systematic assessment tool that provides a quantitative measure of stroke-related neurological deficit. It evaluates 15 items including level of consciousness, gaze, visual fields, facial palsy, motor function, limb ataxia, sensory, language, dysarthria, and extinction/inattention. Scores range from 0 (no deficit) to 42 (maximum deficit). For TIA risk stratification, use [ABCD2 Score](/tools/abcd2-score). Stroke is a major cardiovascular event — assess long-term risk with [ASCVD Risk Calculator](/tools/ascvd-risk). Atrial fibrillation is a leading stroke cause — assess with [CHA2DS2-VASc Score](/tools/cha2ds2-vasc). Assess consciousness level with [Glasgow Coma Scale](/tools/glasgow-coma-scale).
Formula: NIHSS = sum of 15 items (range 0–42)
Administer the 15-item NIHSS in order: level of consciousness (3 items), gaze, visual fields, facial palsy, motor arms, motor legs, ataxia, sensory, language, dysarthria, extinction. Each item has specific instructions.
Assign a score based on the defined criteria for each item. Score what you observe, not what you think the patient can do. Use the first response unless clearly unreliable. Takes 5–8 minutes.
Sum all items (range 0–42). Use the score to determine stroke severity, guide thrombolysis/thrombectomy decisions, communicate with consultants, and monitor for neurological change.
Emergency physicians, stroke teams
Quantify stroke severity within minutes of patient arrival to guide treatment decisions. The NIHSS is the standard language for communicating stroke severity across the care team.
Neurologists, emergency physicians
NIHSS helps determine IV tPA candidacy. Scores of 4+ generally warrant treatment within the time window; scores of 1–3 require assessment of disabling symptoms.
Neurointerventionalists, vascular neurologists
Patients with large vessel occlusion and NIHSS ≥6 are candidates for mechanical thrombectomy up to 24 hours in selected cases. NIHSS helps identify severe strokes warranting intervention.
Stroke unit nurses, hospitalists
Serial NIHSS assessments detect neurological deterioration (increase of 2+ points) or improvement, triggering re-evaluation or indicating treatment response.
Quality coordinators, researchers
NIHSS is a required data element for stroke registries and quality programs (Get With The Guidelines, etc.). It enables benchmarking and outcome analysis.
All clinicians, families
NIHSS provides a standardized framework for discussing stroke severity and expected outcomes with patients and families. Higher scores generally predict worse outcomes.
The NIHSS should be scored based on the actual response to testing, not what you think the patient could do. If a patient can't follow commands due to aphasia, score the LOC commands accordingly.
The NIHSS is biased toward anterior circulation. A patient with basilar artery occlusion may have vertigo, ataxia, and cranial nerve findings but score only 3–5. Don't let a low score delay treatment in posterior stroke.
Language items (aphasia, dysarthria) heavily weight left hemisphere function. Right hemisphere strokes with neglect and visuospatial deficits may be underscore relative to their disability.
Formal NIHSS certification improves inter-rater reliability. Certification is required for clinical trials and recommended for clinical practice. Free online certification is available through the NIH.
The NIHSS manual specifies exact commands and stimuli (e.g., 'Close your eyes,' specific pictures for naming). Using non-standard methods reduces reliability.
Score the first response. If the patient initially answers incorrectly but then self-corrects, score the error. Repeated testing or cueing artificially lowers the score.
Small lacunar strokes, pure sensory strokes, or very mild deficits may score 0. Clinical judgment and imaging are still needed. An NIHSS of 0 rules out moderate-to-severe deficits, not stroke itself.
A patient with NIHSS 2 from isolated hand weakness may be ineligible for thrombolysis, but a patient with NIHSS 2 from isolated aphasia (very disabling for a professor) may warrant treatment. Context matters.
An increase of 2+ points from baseline suggests neurological worsening and should trigger re-evaluation, repeat imaging, and consideration of intervention.
A properly administered NIHSS takes 5–8 minutes. Rushing leads to errors; taking too long delays treatment. Practice until you can reliably complete it in this time frame.
The NIHSS was developed for the NINDS tPA Stroke Trial (NEJM 1995), which established IV alteplase as the standard of care for acute ischemic stroke. It has since been validated in numerous studies and is endorsed by the AHA/ASA, ESO, and virtually all stroke guidelines. Online certification is available through the AHA and is required for clinical trial participation.
Your NIHSS score provides a quantitative measure of stroke severity. A score of 0 indicates no measurable neurological deficit. Scores of 1-4 represent a minor stroke with mild deficits that may not significantly impair daily function. Scores of 5-15 indicate a moderate stroke where patients typically have noticeable deficits in one or more domains such as motor function, speech, or vision. Scores of 16-20 represent a moderate-to-severe stroke, and scores of 21-42 indicate a severe stroke with profound neurological impairment.
The NIHSS score is a key factor in treatment decisions. In general, patients with an NIHSS of 4 or higher presenting within the treatment window are candidates for IV thrombolysis (alteplase or tenecteplase). Patients with large vessel occlusions and an NIHSS of 6 or higher may benefit from mechanical thrombectomy up to 24 hours after onset in selected cases. However, even patients with lower scores may warrant treatment if they have disabling symptoms such as isolated aphasia or hemianopia.
Serial NIHSS assessments are valuable for tracking clinical trajectory. An increase of 2 or more points may signal stroke progression or complications, while a decrease indicates neurological improvement.
The NIHSS should be administered to any patient presenting with signs or symptoms of acute stroke. It is a required component of the acute stroke assessment pathway and is used to determine eligibility for IV thrombolysis and mechanical thrombectomy. Emergency physicians, neurologists, and stroke team nurses should perform this assessment as quickly as possible after patient arrival.
Beyond the acute setting, the NIHSS is used for serial monitoring during hospitalization to detect neurological deterioration or improvement. It is also used as an outcome measure in stroke clinical trials and registries, and at discharge to quantify residual deficits.
The NIHSS has a well-known bias toward anterior circulation (carotid territory) strokes. Posterior circulation strokes affecting the brainstem or cerebellum may produce significant disability (vertigo, ataxia, dysphagia) while generating relatively low NIHSS scores. A patient with a basilar artery occlusion can have a deceptively low score.
The scale also weights left hemisphere function more heavily because of the language items. Right hemisphere strokes causing neglect, anosognosia, or visuospatial deficits may be underscored relative to their true clinical impact. Additionally, the NIHSS does not capture all neurological deficits relevant to stroke, such as cognitive impairment, emotional changes, or pain.
Inter-rater variability exists, particularly for items like ataxia and extinction. Formal NIHSS certification training is recommended to improve scoring consistency. The scale should not be used in isolation to make treatment decisions; clinical judgment, imaging findings, and time from onset are equally important.
For related assessments, see ABCD² Score, Glasgow Coma Scale and Blood Pressure Calculator.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
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