Question 1

What does the NIHSS measure, and what is its range?

Accepted Answer

The NIHSS is a 15-item examination (0–42) that quantifies the size of a neurological deficit in acute stroke, covering level of consciousness, gaze, visual fields, facial and limb strength, ataxia, sensation, language, dysarthria, and inattention. Higher scores mean larger, more disabling deficits and correlate with infarct volume, outcome, and the likelihood of a large-vessel occlusion. It grades severity — it does not by itself establish whether a stroke is present.

Question 2

How is the NIHSS used in acute stroke treatment decisions?

Accepted Answer

The NIHSS is one input among several. It standardizes severity, supports communication, and informs reperfusion discussions — for example, very low scores raise the question of whether a deficit is disabling, and very high scores carry higher hemorrhage risk — but it is not a stand-alone eligibility rule. Decisions about thrombolysis or thrombectomy rest with the treating stroke team applying current AHA/ASA guidance, imaging, time from onset, and the whole clinical picture.

Question 3

Can the NIHSS miss posterior-circulation strokes?

Accepted Answer

Yes. The scale is weighted toward anterior-circulation, dominant-hemisphere deficits (language, motor). Posterior-circulation strokes causing vertigo, ataxia, diplopia, visual-field loss, or cranial-nerve palsies can produce a low NIHSS despite serious, even life-threatening, pathology. A reassuring NIHSS therefore does not exclude a significant posterior-circulation event.

Question 4

Why does the NIHSS score differ for left- vs right-hemisphere strokes?

Accepted Answer

Because several items capture language (best language, naming, dysarthria, LOC questions), dominant (usually left) hemisphere strokes accrue more points than comparably sized non-dominant strokes, which instead cause under-weighted deficits such as neglect. As a result, a left-hemisphere stroke can score higher than a right-hemisphere stroke of similar infarct volume — worth remembering when comparing severity across patients.

Question 5

How does the NIHSS relate to the Glasgow Coma Scale?

Accepted Answer

They are complementary. The GCS measures depth of consciousness in any acute brain injury, whereas the NIHSS grades focal stroke deficit and contains its own consciousness items (1a–1c). A stroke patient can be fully conscious (GCS 15) yet have a high NIHSS from aphasia and hemiparesis, so the two are not interchangeable — use GCS for consciousness and NIHSS for stroke severity.

Question 6

How long does the NIHSS take, and who should perform it?

Accepted Answer

A trained examiner completes it in roughly 5–8 minutes. Reliability depends on standardized technique, so clinicians performing stroke assessments are generally expected to be NIHSS-certified through formal training. Consistent administration matters most when the score is trended over time, because real change must be distinguished from inter-rater variation.

NIHSS Score	Stroke Severity
0	No stroke symptoms
1 – 4	Minor stroke
5 – 15	Moderate stroke
16 – 20	Moderate to severe stroke
21 – 42	Severe stroke

NIHSS Calculator (NIH Stroke Scale)

Neurological Assessment

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