How to Use This Calculator
This calculator reproduces the standardized 15-item NIH Stroke Scale examination. Score each of the 11 grouped items below — running through 1a, 1b, 1c, 2, 3, 4, 5a, 5b, 6a, 6b, 7, 8, 9, 10, and 11 in the order the certified examiner would at the bedside. The calculator automatically sums all 15 fields and renders the 0–42 total, the severity tier, and the matching clinical guidance.
- Item 1a: Level of consciousness — observe before speaking to the patient. Score 0 (alert), 1 (minor stimulation), 2 (repeated stimulation), or 3 (unresponsive).
- Item 1b: Ask the patient's age and the current month. Score the first response only — self-correction does not change the score.
- Item 1c: Ask the patient to open/close eyes and grip/release the non-paretic hand.
- Item 2: Test horizontal gaze by tracking the examiner's finger or a moving object. Only horizontal gaze is scored.
- Item 3: Visual fields by confrontation (finger counting or visual threat in all four quadrants).
- Item 4: Ask the patient to show teeth, raise eyebrows, and close eyes — compare symmetry.
- Items 5a/5b and 6a/6b: Hold each arm 90° (or 45° supine) for 10 seconds; hold each leg 30° supine for 5 seconds. Score drift, effort against gravity, and no movement on each side.
- Item 7: Finger-nose-finger and heel-to-shin — score 0 if the limb is too weak to test (motor ≥3).
- Item 8: Pinprick sensation to face, arms, trunk, and legs — compare sides.
- Item 9: Aphasia — picture description, object naming, sentence reading, spontaneous speech.
- Item 10: Dysarthria — read or repeat words; rate articulation, not comprehension.
- Item 11: Extinction/inattention — bilateral simultaneous stimulation in visual, tactile, auditory, spatial, and personal modalities.
Total possible points = 42. The score and severity tier update live as you select options. Once all 15 fields are scored, the guidance box under the result panel reflects current AHA/ASA treatment pathways for that severity band. In patients whose presentation overlaps with stroke mimics such as PE with hypoxia, syncope, seizure, or toxic-metabolic encephalopathy, see also the Wells PE calculator and the broader stroke vocabulary at the glossary.
About the NIH Stroke Scale
The NIH Stroke Scale (NIHSS) was developed by Thomas Brott and colleagues at the University of Cincinnati and the National Institutes of Health, and published in Stroke in 1989. It was designed to provide a standardized, reproducible, rapid quantitative measure of neurological deficit in acute ischemic stroke — enabling consistent communication among clinicians, objective monitoring of stroke progression, and valid enrollment criteria for clinical trials. Since its validation in the NINDS tPA trial (1995), the NIHSS has been embedded in the eligibility criteria, outcome definitions, and treatment algorithms of virtually every acute stroke intervention. It is mandated in Joint Commission-certified Primary and Comprehensive Stroke Centers.
Severity Interpretation
| NIHSS | Severity | Interpretation | Clinical Guidance |
|---|---|---|---|
| 0 | No Stroke Symptoms | No detectable neurological deficit on the 15-item exam | Does not exclude stroke — posterior circulation and lacunar infarcts frequently score 0. Urgent MRI DWI recommended for acute symptoms. |
| 1–4 | Minor | Minimal deficit; likely ambulating and communicating | Consider IV tPA if deficit is disabling (isolated aphasia, hemianopia, hand weakness). CTA to exclude LVO; thrombectomy generally not indicated unless LVO confirmed. |
| 5–15 | Moderate | Significant neurological deficit; may impair ambulation and ADLs | IV tPA within window (3–4.5 hrs). CTA head/neck for LVO. Thrombectomy if LVO and ASPECTS ≥ 6 (within 24h per DAWN/DEFUSE 3). Stroke unit admission. |
| 16–20 | Moderate to Severe | Large cortical or multi-territory deficit; significant disability expected | Emergent CTA — high likelihood of LVO. Strong thrombectomy candidate if LVO present and within extended window. IV tPA bridge if eligible. ICU admission. |
| 21–42 | Severe | Major hemispheric or brainstem stroke; altered consciousness likely | Emergent thrombectomy for LVO regardless of IV tPA eligibility. Airway management. Consider malignant MCA infarct protocol (decompressive hemicraniectomy criteria). |
Limitations
The NIHSS has several well-documented limitations that inform clinical use:
- Anterior circulation bias: NIHSS is heavily weighted toward large MCA territory strokes; posterior circulation deficits (diplopia, dysphagia, ataxia, isolated field cuts) are incompletely captured — a major basilar artery occlusion can score < 10.
- Intubation and sedation: Pharmacological sedation and neuromuscular blockade invalidate multiple items; document as untestable and rely on imaging rather than down-streaming the patient.
- Training dependence: Reliable scoring requires NIHSS certification (free at strokeassociation.org) — interrater reliability improves substantially with structured training.
- Right-hemisphere stroke underscoring: Extinction/inattention (item 11) partially captures right hemisphere deficits, but executive dysfunction, visuospatial impairment, and anosognosia are poorly measured.
- Aphasia scoring inconsistency: Items 1b, 1c, and 9 can compound in multilingual patients or those with pre-existing aphasia — pre-stroke baselines matter.
- Not a prognostic tool in isolation: Outcome depends on infarct location and volume, collateral flow, time to treatment, age, comorbidities, and reperfusion success — NIHSS alone is insufficient.
In patients whose presentation overlaps with stroke mimics such as massive pulmonary embolism with hypoxia, syncope, or post-ictal Todd paralysis, applying the NIHSS at the bedside — rather than excluding stroke a priori — guides both the imaging decision (CT head, CTA) and the disposition. The Wells PE score remains the appropriate tool for PE pre-test probability; the two scores are complementary, not interchangeable.