What is the probable NIH Stroke Scale (NIHSS) score for a patient presenting with left-sided weakness?

NIHSS Score for Left-Sided Weakness

The probable NIHSS score for a patient presenting with isolated left-sided weakness typically ranges from 2-8 points, depending on the severity and distribution of weakness, but a complete assessment requires evaluating all 11 NIHSS domains to determine the actual score.

Understanding the NIHSS Components

The NIHSS is an 11-part scale ranging from 0-42 points that measures neurologic deficits in a standardized manner 1, 2. For left-sided weakness specifically, you must systematically assess:

Motor Function Scoring (Primary Contributors)

Left arm motor function (Item 5):

• 0 = No drift for 10 seconds
• 1 = Drift but doesn't hit bed
• 2 = Some antigravity effort but cannot sustain
• 3 = No effort against gravity
• 4 = No movement at all 2

Left leg motor function (Item 6):

• 0 = No drift for 5 seconds
• 1 = Drift but doesn't hit bed
• 2 = Some antigravity effort but cannot sustain
• 3 = No effort against gravity
• 4 = No movement at all 2

Additional Scoring Considerations

Beyond motor deficits, you must evaluate:

• Level of consciousness (Items 1A-1C): 0-6 points total
• Gaze: 0-2 points
• Visual fields: 0-3 points
• Facial palsy: 0-3 points (may be present with hemispheric stroke)
• Limb ataxia: 0-2 points
• Sensory: 0-2 points
• Language/aphasia: 0-3 points (typically affected with left hemisphere strokes)
• Dysarthria: 0-2 points
• Extinction/inattention: 0-2 points 1, 2

Critical Clinical Context

Hemispheric Lateralization Matters

Left hemisphere strokes systematically score higher on the NIHSS than right hemisphere strokes of equal volume 3, 4. Research demonstrates that left brain strokes score approximately 4 points higher than right brain strokes due to the scale's emphasis on language function 3. This means:

• Left-sided weakness (from right hemisphere stroke) may produce a lower NIHSS score relative to actual stroke severity
• The median NIHSS for right hemisphere strokes is 15 (range 5-25) 3
• This bias is most pronounced in middle cerebral artery (MCA) territory strokes 4

Practical Scoring Example

A real-world case 5 demonstrated a patient with left-sided weakness presenting with:

• 4/5 strength in left upper extremity (shoulder, elbow, wrist, digits)
• Slight left upper extremity pronator drift
• 2-3/5 strength in left lower extremity
• Initial NIHSS score: 5 points

This represents a "small stroke" (NIHSS <5 indicates small stroke; >20 indicates large stroke) 2.

Prognostic Implications

The NIHSS score directly impacts treatment decisions and outcomes:

• NIHSS <10: 60-70% favorable outcome at 1 year; 3% risk of hemorrhage with thrombolysis 1
• NIHSS >20: Only 4-16% favorable outcome at 1 year; 17% risk of hemorrhage with thrombolysis 1
• NIHSS <6: Forecasts good recovery 6
• NIHSS >16: High probability of death or severe disability 6

Common Pitfalls to Avoid

1. Don't assume isolated weakness equals low score: Associated deficits (sensory loss, neglect, visual field cuts) add points
2. Don't overlook right hemisphere deficits: Spatial neglect and extinction are underrepresented in standard NIHSS item 11 7
3. Don't score based on anatomic interpretation: Score only what you observe, not what you infer 1
4. Don't forget to assess both limbs: The scale includes rating of both affected and unaffected sides 1

Assessment Algorithm

1. Establish alertness and orientation (Items 1A-1C): 0-6 points
2. Test eye movements and visual fields (Items 2-3): 0-5 points
3. Assess facial symmetry (Item 4): 0-3 points
4. Score left arm motor function (Item 5): 0-4 points
5. Score left leg motor function (Item 6): 0-4 points
6. Check for ataxia (Item 7): 0-2 points
7. Test sensation (Item 8): 0-2 points
8. Evaluate language/aphasia (Item 9): 0-3 points
9. Assess articulation (Item 10): 0-2 points
10. Screen for extinction/neglect (Item 11): 0-2 points

Total the scores across all 11 domains for the final NIHSS score 2.