Quantitative Tool for Stroke Severity - The NIH Stroke Scale

Learn about the NIH stroke scale, a vital tool to evaluate and make treatment decisions for stroke patients. This article covers the history, components, administration, interpretation, importance, and limitations of this ubiquitous 11-item neurological exam used in hospitals worldwide to quantify stroke severity.

The NIH stroke scale, or NIHSS, is a tool used by healthcare providers to objectively quantify the impairment caused by a stroke. The NIHSS is composed of 11 items, each of which scores a specific ability between 0 and 4. A higher score indicates more severe neurological deficit. The test provides crucial information to make decisions regarding acute stroke treatment.

The NIHSS was developed in 1983 by neurologists at the National Institute of Health (NIH) in Bethesda, Maryland. The goal was to standardize the clinical assessment of stroke patients in research settings. Prior to the NIHSS, there were nearly 50 published stroke scales. The NIHSS stood out because it was simple, valid across different examiners, reproducible over time, and capable of distinguishing between severe and mild strokes.

The NIHSS evaluates 11 categories including consciousness, eye movement, visual fields, facial movement, arm and leg strength, coordination, sensation, language, speech, and inattention or neglect. Each item is scored between 0 and 4, with 0 indicating normal function. The individual scores are summed to calculate the total NIHSS score, which ranges from 0 to 42; higher values denote more severe neurological deficit.

Only providers certified in administering the NIHSS can conduct the examination. Typically nurses, physicians, or dedicated stroke scale examiners undergo a standardized training program to become certified. The neurological exam takes approximately 5-10 minutes and is conducted at initial emergency department presentation as well as over the next 72 hours to track neurological changes.

The degree of neurological deficit measured by the NIHSS score helps categorize the severity of strokes. Scores ranging 1-4 denote minor stroke. Scores between 5-15 indicate moderate stroke. Scores 16-20 mean severe stroke, while scores above 25 indicate potentially devastating stroke. Tracking NIHSS scores hourly to daily provides critical data to evaluate if patients are improving, worsening or remaining stable.

The NIHSS delivers vital information to determine appropriate acute stroke treatment within the narrow treatment window. The score objectively communicates severity between providers. The scale predicts patient outcomes and guides prognosis. Serial scores gauge response to interventions. Large research trials utilize the widely validated scale to collect consistent data across study sites.

Despite providing a wealth of meaningful stroke data, the NIHSS does have limitations. The score can fluctuate widely early after stroke onset. It may not capture subtle deficits seen in smaller strokes. Mild scores can occur despite disabling stroke if not in a measurable area. And left brain strokes often score higher than equally damaging right hemispheric strokes. Using imaging and clinical judgement in tandem with NIHSS scoring offers the most accurate stroke analysis.

Several facts about nih stroke scale

Stroke assessment

The NIH stroke scale is one of the most widely used methods for initial stroke assessment. It provides a quantitative measure of stroke severity which helps guide treatment decisions.

Acute ischemic stroke

The NIHSS is an integral part of evaluation and management of patients with acute ischemic stroke, which comprises over 80% of all strokes. It assists providers in determining eligibility for IV tPA and mechanical thrombectomy.

Hemorrhagic stroke

For patients with hemorrhagic strokes like subarachnoid and intracerebral hemorrhages, the NIHSS quantifies neurological deterioration which could indicate expanding bleeds requiring urgent intervention.

Stroke mimics

Conditions like seizures, migraines, and toxic metabolic disturbances can appear similar to strokes so differentiating real strokes from “stroke mimics” relies heavily on NIHSS scoring.

Tissue plasminogen activator (tPA)

The clot-busting drug tPA remains the gold standard medical therapy for ischemic strokes. Baseline NIHSS score and exclusions help determine which patients qualify for intravenous thrombolysis with tPA.

Thrombectomy

For large vessel occlusion strokes, mechanical thrombectomy procedures provide the best outcomes. The NIHSS assists physicians in choosing ideal mechanical thrombectomy candidates.

Intracerebral hemorrhage score

While less extensively validated and utilized than the NIHSS, the ICH score provides some useful prognostic information for hemorrhagic strokes using metrics like hemorrhage volume and location.

Modified rankin scale

The modified Rankin scale measures degree of disability or dependence in activities of daily living post-stroke. It is often used in tandem with the baseline NIHSS score to monitor patient improvement.

Barthel index

Complementary to the Rankin scale, the Barthel index is another 100 point stroke disability scale assessing self-care, sphincter control, transfers, ambulation and other parameters as part of post-stroke rehabilitation.

Glasgow coma scale

Whereas NIHSS focuses on neurological deficits from stroke, the 15 point Glasgow coma scale measures level of consciousness which can provide additional insight, especially with large strokes.

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