NIHSS Calculator - NIH Stroke Scale Score
Free online NIHSS calculator with guided scoring for all 15 items. Instant stroke severity classification, tPA eligibility assessment, and thrombectomy threshold guidance.
NIHSS Assessment
Score all 15 items for stroke severity classification
Level of Consciousness
Assess alertness. If not fully alert, determine level of arousal needed.
Ask the month and patient's age. Score initial answer only. Intubated = 1, aphasic/stuporous = 2.
Ask to open/close eyes and grip/release non-paretic hand.
Cranial Nerves & Vision
Test horizontal eye movements only. Use oculocephalic maneuver in uncooperative patients.
Test by confrontation, finger counting, or visual threat as appropriate.
Ask patient to show teeth or raise eyebrows. Use noxious stimulation in poorly responsive patients.
Motor — Arms
Extend arm 90° (sitting) or 45° (supine). Drift = arm falls before 10 seconds.
Extend arm 90° (sitting) or 45° (supine). Drift = arm falls before 10 seconds.
Motor — Legs
Raise leg to 30° (always supine). Drift = leg falls before 5 seconds.
Raise leg to 30° (always supine). Drift = leg falls before 5 seconds.
Coordination & Sensory
Finger-nose-finger and heel-shin tests. Score only if out of proportion to weakness. If paralyzed, score 0.
Test with pinprick. Use grimace/withdrawal in obtunded patients.
Language & Speech
Patient describes picture, names items, reads sentences. Score BEST effort (exception to general rule).
Patient reads/repeats standard word list. Assess clarity of articulation.
Neglect
Double simultaneous stimulation (visual and tactile).
NIHSS Score
Enter values to calculate
About This Calculator
What is the NIH Stroke Scale (NIHSS)?
The NIH Stroke Scale is a 15-item neurologic examination used to evaluate the severity of acute ischemic stroke. Developed by Thomas Brott and Harold P. Adams Jr. at the University of Cincinnati in 1989, it is the most widely used stroke severity assessment tool worldwide.
How does the NIHSS work?
The NIHSS systematically evaluates key neurological functions including level of consciousness, eye movements, visual fields, facial symmetry, motor strength, coordination, sensation, language, speech, and spatial awareness. Each item is scored on an ordinal scale, and the total score ranges from 0 (no deficits) to 42 (maximum deficits). Higher scores indicate more severe stroke.
Clinical Applications
- Guides acute treatment decisions including IV thrombolysis (tPA) and mechanical thrombectomy eligibility
- Predicts patient outcomes at 3 months with strong correlation (r = 0.79)
- Facilitates standardized communication between healthcare providers
- Required for serial neurological assessments post-thrombolysis
- Used in stroke clinical trials as a primary or secondary endpoint
Scoring Interpretation
A score of 0 indicates no stroke symptoms, 1–4 indicates minor stroke, 5–15 indicates moderate stroke, 16–20 indicates moderate-to-severe stroke, and 21–42 indicates severe stroke. Each 1-point increase corresponds to a 17% decreased likelihood of excellent outcome at 3 months.
Formula
NIHSS = 1a + 1b + 1c + 2 + 3 + 4 + 5a + 5b + 6a + 6b + 7 + 8 + 9 + 10 + 11 (items scored UN contribute 0)Sum of all 15 items. Items marked UN (untestable due to amputation, joint fusion, or intubation) do not contribute to the total score. Maximum possible score is 42 points.
Clinical Considerations
- •NIHSS 0 does NOT rule out stroke — over 75% of posterior circulation strokes present with NIHSS 0–5.
- •Left hemisphere bias: language items = 7/42 points, neglect = 2/42. Right hemisphere strokes with equal lesion volume score lower.
- •Up to 30% of large vessel occlusion (LVO) patients present with low NIHSS scores.
- •Do not withhold tPA solely based on low NIHSS — treat if symptoms are disabling regardless of score.
- •"Rapidly improving" symptoms should NOT automatically exclude from thrombolysis if deficits remain disabling.
Limitations
- •Poor posterior circulation assessment — truncal ataxia, Horner syndrome, nystagmus, vertical gaze palsy, and bulbar signs are not captured.
- •Inter-rater variability: limb ataxia (kappa 0.15), facial palsy (kappa 0.22), dysarthria (kappa 0.46) have low reliability.
- •Cannot capture cognitive deficits, fatigue, or emotional changes.
- •20% ceiling effect at 6 months for outcome prediction.
- •Ataxia minimally weighted (max 2 points) relative to clinical significance.
- •Scoring discrepancies common between neurologists and nurses (34.7% have ≥ 2 point differences).
Interpretation Guide
| Range | Classification | Recommendation |
|---|---|---|
| <-0 | No Stroke Symptoms | No deficits on exam. Note: NIHSS 0 does NOT rule out stroke — >75% of posterior circulation strokes present with NIHSS 0–5. Pursue imaging if clinical suspicion remains. |
| 1-4 | Minor Stroke | Minor deficits. IV thrombolysis still indicated if within window and symptoms are disabling. Do not withhold tPA solely based on low NIHSS. Up to 30% of LVO patients present with low NIHSS. |
| 5-15 | Moderate Stroke | Moderate stroke. IV thrombolysis indicated within treatment window. Evaluate for LVO and mechanical thrombectomy (NIHSS ≥ 6 with ICA/M1 occlusion). Admit to stroke unit. |
| 16-20 | Moderate-to-Severe Stroke | Moderate-to-severe stroke. Strong probability of death or severe disability. IV thrombolysis and mechanical thrombectomy evaluation urgently indicated. ICU-level care recommended. |
| 21-42 | Severe Stroke | Severe stroke. Very high probability of death or severe disability. Discuss goals of care. Consider thrombectomy if LVO confirmed. In 3–4.5h window: tPA may be considered if NIHSS < 25. |
Frequently Asked Questions
What is the NIH Stroke Scale (NIHSS)?
The NIH Stroke Scale is a standardized 15-item neurologic examination used to evaluate the severity of acute ischemic stroke. It assesses level of consciousness, eye movements, visual fields, facial symmetry, motor strength, coordination, sensation, language, speech, and spatial neglect. Scores range from 0 (no deficits) to 42 (maximum deficits).
How do you calculate the NIHSS score?
The NIHSS is calculated by summing scores across all 15 items (labeled 1a through 11). Each item is scored based on the patient's examination findings, with higher scores indicating more severe deficits. Items marked UN (untestable due to amputation, fusion, or intubation) contribute 0 points to the total.
What NIHSS score qualifies for tPA?
There is no minimum NIHSS score required for IV tPA within 3 hours of symptom onset. In the 3–4.5 hour window, NIHSS should be < 25. "Rapidly improving" symptoms should NOT automatically exclude treatment if deficits remain disabling. The key consideration is whether symptoms are disabling, not the absolute score.
What is a normal NIHSS score?
A score of 0 indicates no measurable neurological deficit. However, NIHSS 0 does NOT rule out stroke — over 75% of posterior circulation stroke patients have NIHSS scores of 0–5. If clinical suspicion exists, pursue imaging regardless of the NIHSS score.
What NIHSS score is considered severe?
NIHSS 21–42 is classified as severe stroke, with a strong probability of death or severe long-term disability. NIHSS 16–20 is moderate-to-severe. Each 1-point increase in NIHSS corresponds to a 17% decreased likelihood of excellent outcome at 3 months.
What NIHSS score requires thrombectomy?
Within 6 hours of onset, mechanical thrombectomy is generally indicated for NIHSS ≥ 6 with ASPECTS ≥ 6 and confirmed ICA or proximal MCA (M1) occlusion. In the 6–24 hour window, NIHSS ≥ 6 with favorable imaging selection criteria. For posterior circulation (basilar), NIHSS ≥ 10 within 24 hours.
How often should NIHSS be assessed?
Post-tPA protocol: every 15 minutes during and 1 hour after the infusion, then every 30 minutes for hours 2–8, then hourly for hours 8–24. After 24 hours, per institutional protocol (typically every 4–8 hours). A change of ≥ 2 points in 24 hours is considered clinically significant.
How long does the NIHSS take to administer?
Bedside NIHSS administration takes a mean of 6.55 minutes (range 4–12 minutes). Telestroke assessment takes a mean of 9.70 minutes (range 6–18 minutes). The exam should not delay emergent treatment decisions.
What is the difference between NIHSS and mNIHSS?
The modified NIHSS (mNIHSS) is an 11-item version (score 0–31) that removes facial palsy, limb ataxia, dysarthria, and level of consciousness — the four items with the worst inter-rater reliability. The mNIHSS has improved reliability (71% excellent agreement vs. 54% for full NIHSS) and is highly correlated with the full NIHSS.
Can nurses perform the NIHSS?
Yes. The NIHSS was validated for use by non-neurologists including nurses. Goldstein & Samsa (1997) showed ICC of 0.93–0.95 across physicians and non-physicians. Nurses must typically certify annually. However, 34.7% of neurologist-RN scoring pairs show clinically meaningful differences (≥ 2 points), with aphasia being the strongest predictor of discrepancy.
Does NIHSS predict stroke outcome?
Yes. The NIHSS is a strong predictor of stroke outcome with a correlation of r = 0.79 at 3 months (Adams et al. 1999). NIHSS < 6 has a strong probability of good recovery. NIHSS ≥ 16 has a strong probability of death or severe disability. Regarding discharge: NIHSS < 5 leads to ~80% discharged home, 6–13 to inpatient rehabilitation, and > 13 to nursing home/long-term care.
What are the limitations of the NIHSS?
Key limitations include: (1) Left hemisphere bias — language items account for 7/42 points while neglect only 2/42, meaning right hemisphere strokes with similar lesion volumes score lower. (2) Poor posterior circulation capture — >75% of posterior strokes have NIHSS 0–5. (3) Items with poor inter-rater reliability including limb ataxia (kappa 0.15) and facial palsy (kappa 0.22). (4) Cannot capture cognitive deficits, fatigue, or emotional changes.
What is a minor stroke on the NIHSS?
NIHSS 1–4 is classified as a minor stroke. Approximately 80% of patients with minor stroke are discharged home. However, do not assume low NIHSS means benign — up to 30% of large vessel occlusion (LVO) patients present with low NIHSS scores, and these patients can deteriorate rapidly.
Is NIHSS certification required?
NIHSS certification is required for nurses performing serial neurological assessments and for investigators in stroke clinical trials. Nurses typically must certify annually through standardized video-based training. Neurologists have no universal mandatory certification requirement, though many institutions require it.
References
1. Brott T, Adams HP Jr, Olinger CP, et al.. Measurements of acute cerebral infarction: a clinical examination scale. Stroke. 1989
View Source →2. Adams HP Jr, Davis PH, Leira EC, et al.. Baseline NIH Stroke Scale score strongly predicts outcome after stroke. Neurology. 1999
View Source →3. Goldstein LB, Samsa GP. Reliability of the NIH Stroke Scale: Extension to non-neurologists. Stroke. 1997
View Source →4. Powers WJ, Rabinstein AA, Ackerson T, et al.. Guidelines for the Early Management of Patients With Acute Ischemic Stroke (2019 Update). Stroke. 2019
View Source →5. Various Authors. Pitfalls of NIHSS: A Critical Review. PMC. 2024
View Source →6. Various Authors. Left hemisphere bias of the NIHSS. PMC. 2022
View Source →Last updated: 2026-02-24
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