• Baseline quantification of neurological deficit in Acute Ischemic Stroke (AIS).
• Primary tool for reperfusion eligibility (IV Thrombolysis / Thrombectomy).
• Validated for patient handoff between ER and Neurology teams (Cummock, 2023).
• Predicts hospital disposition and 3-month functional outcomes (mRS).

Perform at T0 (presentation), 2h post-reperfusion, 24h post-onset, and at discharge. A change of ±4 points is clinically significant, often requiring repeat imaging to rule out hemorrhagic transformation.

• 1989 (Brott et al.): Inception of the 15-item scale to standardize stroke trial results.
• 2009 (Meyer & Lyden): Proposed the mNIHSS to eliminate items with poor inter-rater reliability (Ataxia, Facial Palsy, Dysarthria) and minimize lateralization bias.
• 2023 (Cummock et al.): Real-world study at a Comprehensive Stroke Center (n=1,946) proved "Excellent" reliability (ICC = 0.95) between ER and Neuro teams, supporting score substitution in registries.
• 2025 (Alamri et al.): Validated the r-NIHSS (Retrospective NIHSS) scoring tool, allowing clinicians to reconstruct valid NIHSS scores from medical records with ICC = 0.99.

If p-NIHSS is undocumented, use the following mapping for retrospective assessment (Alamri et al., 2025):

• NIHSS ≥ 6: High sensitivity for Large Vessel Occlusion (LVO). Request immediate CTA/MRA.
• NIHSS ≥ 15: High specificity for proximal LVO (ICA/M1). Consider "Bypass to Thrombectomy" protocols.
• Lateralization Bias: NIHSS often under-represents right-hemisphere (non-dominant) strokes; a score of 4 in a right-hemisphere stroke often masks a larger infarct volume than 4 in a left-hemisphere stroke.