NIH Stroke Scale Calculator

Understanding the National Institutes of Health Stroke Scale (NIHSS)

The National Institutes of Health Stroke Scale (NIHSS) is the global gold standard clinical assessment tool used to objectively quantify neurological impairment in acute ischemic stroke and intracerebral hemorrhage. Developed by the National Institute of Neurological Disorders and Stroke (NINDS), it provides a rapid, standardized 11-domain neurological examination designed for emergency physicians, neurologists, and stroke code teams.

The NIHSS score serves three fundamental purposes in modern emergency stroke workflows:

1. Acuity Stratification: Rapidly differentiates minor, moderate, severe, and very severe stroke presentations.
2. Reperfusion Eligibility: Informs decisions regarding intravenous thrombolytic administration (such as tenecteplase or alteplase) and endovascular thrombectomy (EVT) for large vessel occlusions (LVO).
3. Outcome Prediction: Strongly correlates with 3-month functional independence (modified Rankin Scale) and hospital discharge disposition.

The 11 Examination Domains of the NIHSS

The NIHSS evaluates key vascular territories corresponding to middle, anterior, and posterior cerebral circulations across 15 scoreable elements (scoring from 0 to 42):

Score Classification and Prognosis

• 0: No stroke symptoms.
• 1 to 4 (Minor Stroke): Mild deficit; generally favorable functional recovery with over 70% of patients discharged home without assisted care.
• 5 to 15 (Moderate Stroke): Moderate impairment; high benefit from acute intravenous thrombolysis and dedicated stroke unit care.
• 16 to 20 (Severe Stroke): Substantial neurological injury; high likelihood of large vessel occlusion; expedited thrombectomy triage indicated.
• 21 to 42 (Very Severe Stroke): Massive hemispheric or basilar occlusion; carries high in-hospital mortality and severe long-term disability risk.

For other critical triage and acute assessment calculators, explore our MEWS Score Calculator or NEDOCS Calculator.