NIH Stroke Scale (NIHSS) Calculator
1a. Level of Consciousness
The investigator must choose a response if a full evaluation is prevented by such obstacles as an endotracheal tube, language barrier, orotracheal trauma/bandages.
Keenly responsive
Not alert, but arousable by minor stimulation to obey, answer, or respond
Requires repeated stimulation to attend, or is obtunded and requires strong or painful stimulation to make movements
Responds only with reflex motor or autonomic effects or totally unresponsive, flaccid, and areflexic
What is the NIH Stroke Scale?
The National Institutes of Health Stroke Scale (NIHSS) is a systematic assessment tool that provides a quantitative measure of stroke-related neurologic deficit. It was developed to provide a consistent and reliable assessment method for use in clinical trials and patient care.
The NIHSS is composed of 11 items that evaluate specific abilities, with scores ranging from 0 to 42. A higher score indicates greater severity of stroke.
Clinical Significance
The NIHSS serves several important clinical purposes:
- Helps quantify the severity of a stroke
- Facilitates communication among healthcare providers
- Helps identify patients who may benefit from specific interventions
- Predicts both short and long-term outcomes
- Monitors neurological changes during the acute phase
The scale is widely used in both clinical practice and research settings, and is often a key component in determining eligibility for acute stroke treatments.
Score Interpretation
| Score | Stroke Severity | Interpretation |
|---|---|---|
| 0 | No stroke symptoms | No stroke or completely recovered |
| 1-4 | Minor stroke | Minimal impairment, generally good prognosis |
| 5-15 | Moderate stroke | Moderate impairment, variable prognosis |
| 16-20 | Moderate to severe stroke | Significant impairment, guarded prognosis |
| 21-42 | Severe stroke | Severe impairment, poor prognosis |
Clinical Applications
Acute Treatment Decisions
The NIHSS helps guide decisions about thrombolytic therapy (tPA) and endovascular interventions. Patients with scores between 4-25 are often considered for these treatments, though specific criteria may vary.
Prognosis
Baseline NIHSS scores strongly predict outcomes at 3 months. Approximately 60-70% of patients with scores <10 have favorable outcomes, while only 4-16% of those with scores >20 achieve good recovery.
Monitoring
Serial NIHSS assessments help monitor neurological changes during hospitalization, allowing for timely intervention if deterioration occurs.
Discharge Planning
NIHSS scores help determine appropriate discharge disposition (home, rehabilitation, skilled nursing facility) and anticipate resource needs.
Limitations
Despite its utility, the NIHSS has several limitations:
- It is weighted toward left hemisphere strokes (language deficits score more points than neglect)
- It may underestimate posterior circulation strokes (brainstem, cerebellum)
- It does not directly assess distal hand function, memory, or cognition
- Proper administration requires training and certification
- Pre-existing neurological deficits can confound interpretation
Clinical judgment should always be used alongside the NIHSS score when making treatment decisions.
Evidence and Validation
The NIHSS was developed in the late 1980s and has been extensively validated. It has excellent inter-rater reliability when administered by trained personnel and strong predictive validity for both short and long-term outcomes.
Multiple studies have confirmed its utility in predicting functional outcomes, mortality, length of stay, and discharge disposition after stroke.
References
- Brott T, Adams HP Jr, Olinger CP, et al. Measurements of acute cerebral infarction: a clinical examination scale. Stroke. 1989;20(7):864-870.
- Lyden P, Brott T, Tilley B, et al. Improved reliability of the NIH Stroke Scale using video training. NINDS TPA Stroke Study Group. Stroke. 1994;25(11):2220-2226.
- Adams HP Jr, Davis PH, Leira EC, et al. Baseline NIH Stroke Scale score strongly predicts outcome after stroke: A report of the Trial of Org 10172 in Acute Stroke Treatment (TOAST). Neurology. 1999;53(1):126-131.
- Kwiatkowski TG, Libman RB, Frankel M, et al. Effects of tissue plasminogen activator for acute ischemic stroke at one year. National Institute of Neurological Disorders and Stroke Recombinant Tissue Plasminogen Activator Stroke Study Group. N Engl J Med. 1999;340(23):1781-1787.
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