Nih Stroke Scale Calculator

The NIH Stroke Scale quantifies acute neurological deficit by summing 15 separately scored items, giving a total from 0 to 42. The items sample the territories most often affected by anterior circulation ischemia: level of consciousness and two orientation and command tasks, horizontal gaze, visual fields, facial movement, motor drift in each arm and leg, limb ataxia, sensation, language, dysarthria, and extinction or inattention. Item weights are deliberately unequal - each limb can contribute up to 4 points and language up to 3, so motor and language deficits dominate the total. Scoring rules are strict and unusual: examiners record the first response, do not coach, and score what the patient actually does rather than what the examiner believes they could do. In practice a score of 0 to 4 is minor, 5 to 15 moderate, 16 to 20 moderate to severe, and above 20 severe. The number is used less as a diagnosis than as a decision input: baseline NIHSS predicts 3-month disability, scores above roughly 6 raise the likelihood of a large vessel occlusion and prompt urgent vessel imaging for thrombectomy, and thresholds appear in trial eligibility criteria. Two structural limitations are well documented. The scale is left-hemisphere weighted because aphasia items carry more points than neglect items, so a dominant hemisphere infarct scores higher than a comparably disabling right hemisphere infarct. Posterior circulation and brainstem strokes are systematically under-scored because vertigo, diplopia, gait ataxia, and cranial nerve palsies are barely represented, meaning a patient with a basilar occlusion can present with a deceptively low total.

The scale was created for the first National Institute of Neurological Disorders and Stroke trial of acute stroke therapy. Thomas Brott, Harold P. Adams Jr., Charles Olinger, and colleagues at the University of Cincinnati published it in Stroke in 1989 as Measurements of Acute Cerebral Infarction: A Clinical Examination Scale. They drew items from three existing instruments - the Toronto Stroke Scale, the Oxbury initial severity scale, and the Cincinnati Stroke Scale - and validated the composite by having neurologists, house officers, and nurses score the same videotaped patients, showing that a structured exam could be applied reproducibly by non-neurologists in about seven minutes. Its adoption was driven by the 1995 NINDS trial of intravenous recombinant tissue plasminogen activator, which used the scale as its primary severity measure and made an NIHSS assessment a de facto prerequisite for thrombolysis. Later work trimmed redundancy: Lyden and colleagues showed some items had poor reliability, which led to the modified NIHSS and to the standardized training and certification videos distributed through NINDS and the American Heart Association. The scale then carried into the endovascular era, appearing in the enrollment criteria of the 2015 thrombectomy trials and in the DAWN and DEFUSE 3 late-window trials, where NIHSS was paired with imaging-based mismatch criteria. It is now embedded in Get With The Guidelines stroke registries and in prehospital scales derived from it, including RACE and the Cincinnati Prehospital Stroke Scale.