NIH Stroke Scale
Formal Definition
The National Institutes of Health Stroke Scale (NIHSS): a standardized 15-item neurological assessment tool used to quantify stroke severity, covering level of consciousness, gaze, visual fields, facial palsy, motor arm/leg, limb ataxia, sensation, language, dysarthria, and extinction; scored 0–42 (0 = normal, >25 = severe).
How It's Used on the Ward
"NIHSS" or "what's the NIH score" — the universal language of stroke severity; guides tPA and thrombectomy eligibility decisions.
Example
""Patient woke up with right hemiplegia and aphasia, last known well 90 minutes ago. NIHSS is 16 — activating the stroke protocol, CT head negative for bleed, giving tPA and calling interventional neurology for potential thrombectomy.""
Clinical Context
NIHSS ≥6 is the general threshold for mechanical thrombectomy consideration. tPA (alteplase) is given for eligible patients within 3–4.5 hours of last known well if no hemorrhage on CT. Stroke certifications (Joint Commission) require NIHSS to be documented serially. Know the scale cold before a stroke rotation: being able to score quickly and accurately in an emergency is expected. Higher scores do not always predict worse outcomes — large vessel occlusion with thrombectomy can have dramatic recoveries even from NIHSS 20+.
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