NIH Stroke Scale (NIHSS) Calculator

How to Use This Calculator

1. Assess each of the 15 NIHSS items per standardized examination instructions.
2. Select the correct score for each item from the dropdown.
3. Total NIHSS score, severity category, and tPA/thrombectomy notes update instantly.
4. Use Thrombectomy tab to assess LVO likelihood and eligibility criteria.

Formula

Example

Frequently Asked Questions

• What is the NIHSS and how is it used in acute stroke care? ▼
  The National Institutes of Health Stroke Scale (NIHSS) is a standardized, validated neurological assessment tool developed to quantify the severity of acute ischemic stroke at bedside. It was developed by Brott et al. in the late 1980s and has become the universal language of acute stroke severity in clinical practice, clinical trials, and quality improvement programs worldwide. The NIHSS evaluates 15 neurological domains: level of consciousness (items 1a, 1b, 1c), gaze (item 2), visual fields (item 3), facial palsy (item 4), motor arm left and right (items 5a, 5b), motor leg left and right (items 6a, 6b), limb ataxia (item 7), sensory (item 8), language (item 9), dysarthria (item 10), and extinction or inattention (item 11). Each item is scored using a standardized ordinal scale with specific examination criteria. Total scores range from 0 (no stroke symptoms) to 42 (maximum severity). The NIHSS is used to guide immediate treatment decisions including tPA eligibility and thrombectomy planning, to communicate stroke severity among providers, to monitor neurological improvement or deterioration over time, and as a primary outcome measure in stroke clinical trials.
• What NIHSS score qualifies a patient for tPA (alteplase) treatment? ▼
  Intravenous tPA (alteplase or tenecteplase) eligibility based on NIHSS is nuanced and requires clinical judgment rather than a strict score cutoff. The most important consideration is whether the neurological symptoms are disabling. For patients with NIHSS greater than or equal to 4, IV tPA is generally indicated within the 0-4.5 hour time window from symptom onset if no contraindications are present. At the lower end (NIHSS 1-3), minor stroke, tPA eligibility is less clear-cut: the 2019 AHA/ASA guidelines note that tPA treatment for minor but disabling symptoms is reasonable, while tPA for clearly non-disabling symptoms is not typically recommended. The PRISMS trial (2018) found no significant benefit of alteplase over aspirin in patients with NIHSS 0-5 classified as non-disabling, though subgroup analyses suggested benefit in disabling symptoms. For severe strokes with NIHSS above 25, tPA has a relative contraindication in some guidelines due to concerns about hemorrhagic transformation, though this is not an absolute contraindication and should be evaluated case-by-case. Critically, tPA eligibility requires checking blood pressure below 185/110 mmHg, glucose above 50 mg/dL, platelet count above 100,000, and INR below 1.7, in addition to the time window and symptom severity assessment.
• What NIHSS score suggests large vessel occlusion (LVO) requiring thrombectomy? ▼
  NIHSS score is one of several tools used to screen for large vessel occlusion (LVO) as a trigger for urgent computed tomographic angiography (CTA) of the head and neck, which is the definitive test to confirm LVO. Multiple studies have evaluated the relationship between NIHSS and LVO probability. As a general rule, NIHSS 6 or greater is associated with a substantially higher probability of LVO, and virtually all centers would perform urgent CTA in patients with NIHSS at or above this threshold. The NIHSS-LVO screening tools such as FAST-ED (Field Assessment Stroke Triage for Emergency Destination) and RACE (Rapid Arterial occlusion Evaluation) further refine field triage, but NIHSS remains central to in-hospital decision-making. For mechanical thrombectomy eligibility specifically, the pivotal HERMES meta-analysis showed benefit for patients with NIHSS 6 or higher and proven proximal occlusion within 0-6 hours. The DAWN trial used NIHSS 10 or higher (for age 80 and above) or 10 or higher (for age below 80 with core infarct 31-51 mL) in the 6-24 hour window. The DEFUSE-3 trial used NIHSS 6 or higher in the 6-16 hour window with CT perfusion imaging selection. A low NIHSS (1-5) does not exclude LVO, particularly in basilar occlusion or posterior circulation strokes where the NIHSS systematically underestimates deficit severity — clinical presentation must always complement the numerical score.
• How are the NIHSS motor items scored correctly? ▼
  The motor arm and leg items (items 5a, 5b, 6a, 6b) are among the most clinically important components of the NIHSS and must be assessed using the standardized technique to ensure reproducibility. For the motor arm, the patient is asked to extend the arm at 90 degrees (if sitting) or 45 degrees (if supine) with palms down, and to maintain this position for 10 seconds. The examiner should not assist the patient in holding position. Scoring: 0 = arm maintains position for 10 seconds (no drift); 1 = arm drifts before 10 seconds but does not hit the bed (drift present, gravity not defeated); 2 = arm falls to the bed within 10 seconds but patient shows some effort against gravity; 3 = no effort against gravity, arm falls immediately but patient has some movement; 4 = no movement at all. For the motor leg, the supine patient is asked to maintain the leg at 30 degrees for 5 seconds (note: 5 seconds for leg vs 10 seconds for arm). The same 0-4 scoring applies. Crucially, if a limb is amputated or has a joint fusion, the item is marked as "not applicable" using the specific NT code on the NIHSS scoring form — it does not score 0. Examiner training and certification (available through NIHSS online training at nihss.trainingcampus.net) is strongly recommended to ensure inter-rater reliability, as untrained examiners show substantially higher variability.
• How does NIHSS correlate with expected stroke outcomes and prognosis? ▼
  NIHSS score at presentation is one of the strongest predictors of functional outcome at 90 days following acute ischemic stroke. Multiple studies have established the relationship between admission NIHSS and 90-day modified Rankin Scale (mRS) outcomes in both treated and untreated patients. For minor strokes (NIHSS 1-4), the majority of patients achieve good functional outcome (mRS 0-2) at 90 days, with or without reperfusion therapy, as spontaneous recovery is common in this group. For moderate strokes (NIHSS 5-15), outcomes are highly variable and depend critically on whether reperfusion is achieved — patients who achieve TICI 2b or 3 recanalization with thrombectomy within 0-6 hours have substantially better outcomes (approximately 50-70% achieving mRS 0-2) compared to those treated with IV tPA alone (approximately 30-45%) or best medical therapy (15-25%). For moderate-severe strokes (NIHSS 16-20), good functional outcomes occur in 20-40% with successful thrombectomy. For severe strokes (NIHSS above 20), most patients have poor outcomes (mRS 4-6) even with successful thrombectomy, though young patients with large penumbra and small core infarct identified on CT perfusion imaging can still achieve meaningful recovery. The "10-point rule" from clinical observation — each 10-point increase in NIHSS roughly doubles the odds of poor outcome at 90 days — is a useful clinical heuristic but not a precise prognostic tool.

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