The NIH Stroke Scale (NIHSS) is a systematic assessment tool used to quantify the severity of neurological deficits in acute stroke patients. It provides a weighted score based on specific clinical findings, allowing standardised evaluation and communication. Components of the NIHSS: Level of consciousness: Assesses alertness, responsiveness to questions and commands (0-3 points). Best gaze: Evaluates horizontal eye movements (0-2 points). Visual fields: Tests for hemianopia or quadrantanopia (0-3 points). Facial palsy: Assesses symmetry of facial movements (0-3 points). Motor arm and leg: Measures limb strength on each side separately (0-4 points per limb). Limb ataxia: Checks for coordination deficits (0-2 points). Sensory: Evaluates sensation to pinprick (0-2 points). Language: Assesses aphasia through naming, repetition, and comprehension tasks (0-3 points). Dysarthria: Evaluates speech clarity (0-2 points). Extinction and inattention (neglect): Tests for hemispatial neglect (0-2 points). The total NIHSS score ranges from 0 to 42, with higher scores indicating more severe neurological impairment. It is used clinically to: Guide thrombolysis eligibility — typically, moderate to severe strokes (NIHSS ≥6) are considered for treatment. Predict prognosis — higher scores correlate with increased morbidity and mortality. Monitor changes over time — serial scoring helps assess progression or improvement. The NIHSS is weighted because different items contribute variably to the total score depending on their impact on function. For example, motor deficits carry more weight than mild sensory loss. This weighting allows a nuanced quantification rather than a simple checklist. In summary, the NIHSS is not merely a checklist but a weighted scale that quantifies stroke severity by assessing multiple neurological domains systematically.