Clinical Overview
The National Institutes of Health Stroke Scale (NIHSS) is the gold standard clinical assessment tool for evaluating acute stroke patients. It provides a quantitative measure of stroke-related neurologic deficit. It is used universally in emergency departments to evaluate stroke severity, determine eligibility for acute interventions (like IV alteplase or mechanical thrombectomy), and monitor for neurological deterioration.
Pathophysiology & Evidence
The NIHSS systematically tests various territories of the brain. For example, testing for aphasia evaluates the dominant middle cerebral artery (MCA) territory, while testing for neglect evaluates the non-dominant MCA territory. Gaze deviation can point to frontal eye field ischemia.
Formula Breakdown
The scale ranges from 0 to 42:
Total Score = Sum of 15 Neurological Exam Parameters
A score of 0 indicates normal function, 1-4 is a minor stroke, 5-15 is moderate, 16-20 is moderate to severe, and 21-42 is severe.