Detailed Scoring of the National Institutes of Health Stroke Scale (NIHSS)
The National Institutes of Health Stroke Scale (NIHSS) is a standardized 15-item neurological assessment tool that evaluates stroke severity with scores ranging from 0-42, with higher scores indicating greater stroke severity. 1
NIHSS Components and Scoring
The NIHSS consists of the following components:
| Item | Assessment | Score Range |
|---|---|---|
| 1A | Level of consciousness | 0-3 |
| 1B | Orientation questions | 0-2 |
| 1C | Response to commands | 0-2 |
| 2 | Gaze | 0-2 |
| 3 | Visual fields | 0-3 |
| 4 | Facial movement | 0-3 |
| 5 | Motor function (arm) - Left & Right | 0-4 each |
| 6 | Motor function (leg) - Left & Right | 0-4 each |
| 7 | Limb ataxia | 0-2 |
| 8 | Sensory | 0-2 |
| 9 | Language | 0-3 |
| 10 | Articulation | 0-2 |
| 11 | Extinction/inattention | 0-2 |
| Total NIHSS Score | 0-42 |
Detailed Scoring Criteria
1. Level of Consciousness
1A. Level of Consciousness
- 0: Alert, keenly responsive
- 1: Not alert but arousable with minimal stimulation
- 2: Not alert, requires repeated stimulation to attend
- 3: Unresponsive or responds only with reflexes
1B. LOC Questions (Ask month and age)
- 0: Answers both correctly
- 1: Answers one correctly
- 2: Answers neither correctly
1C. LOC Commands (Open/close eyes, grip/release hand)
- 0: Performs both tasks correctly
- 1: Performs one task correctly
- 2: Performs neither task correctly
2. Best Gaze
- 0: Normal
- 1: Partial gaze palsy
- 2: Forced deviation or total gaze paresis
3. Visual Fields
- 0: No visual loss
- 1: Partial hemianopia
- 2: Complete hemianopia
- 3: Bilateral hemianopia or blindness
4. Facial Palsy
- 0: Normal
- 1: Minor paralysis
- 2: Partial paralysis
- 3: Complete paralysis
5. Motor Arm (Left and Right scored separately)
- 0: No drift
- 1: Drift before 10 seconds
- 2: Falls before 10 seconds
- 3: No effort against gravity
- 4: No movement
6. Motor Leg (Left and Right scored separately)
- 0: No drift
- 1: Drift before 5 seconds
- 2: Falls before 5 seconds
- 3: No effort against gravity
- 4: No movement
7. Limb Ataxia
- 0: Absent
- 1: Present in one limb
- 2: Present in two or more limbs
8. Sensory
- 0: Normal
- 1: Mild to moderate loss
- 2: Severe to total loss
9. Best Language
- 0: No aphasia
- 1: Mild to moderate aphasia
- 2: Severe aphasia
- 3: Mute or global aphasia
10. Dysarthria
- 0: Normal
- 1: Mild to moderate
- 2: Severe, unintelligible or mute
11. Extinction and Inattention
- 0: No abnormality
- 1: Inattention or extinction to one sensory modality
- 2: Severe hemi-inattention or extinction to multiple modalities
Clinical Interpretation and Prognostic Value
The NIHSS score correlates with stroke severity and prognosis:
- <5: Small stroke with good recovery potential
- 5-15: Moderate stroke
- >16: Severe stroke with high probability of death or severe disability
- >20: Large stroke with only 4-16% favorable outcomes at 1 year 1
Important Considerations
Hemispheric Bias: The NIHSS may underestimate right hemisphere stroke severity compared to left hemisphere strokes of similar volume. For a given NIHSS score, right hemisphere strokes typically have approximately double the volume of left hemisphere strokes 2.
Cutoff Values for Favorable Outcomes: The optimal cutoff scores for predicting favorable outcomes (modified Rankin Scale ≤2 at 3 months) are:
- ≤5 for posterior circulation strokes (sensitivity 84%, specificity 81%)
- ≤8 for anterior circulation strokes (sensitivity 80%, specificity 82%) 3
Large Vessel Occlusion Prediction: NIHSS cutoff scores of ≥6-7 are commonly used to predict large vessel occlusion with sensitivities of 68-81% and specificities of 77-79% 4.
Quality of Life Impact: The NIHSS is more sensitive to motor deficits than non-motor deficits. Limb paresis explains 17.5-24.1% of variance in quality of life scores, while aphasia (10.0%), hemianopia (10.8%), and neglect (8.9%) have less impact on quality of life measurements 5.
Administration Time: The NIHSS can be administered in 5-8 minutes, making it efficient for acute stroke assessment 6.
Certification: Healthcare providers should be certified in NIHSS administration to ensure reliability, with certification now available through online platforms 7.