What is the significance of the National Institutes of Health Stroke Scale (NIHSS) score in managing acute ischemic stroke patients?

Significance of the NIHSS Score in Managing Acute Ischemic Stroke Patients

The National Institutes of Health Stroke Scale (NIHSS) is a critical standardized assessment tool that strongly predicts patient outcomes after stroke, with scores >16 forecasting high probability of death or severe disability and scores <6 indicating good recovery prospects, making it essential for guiding acute treatment decisions including thrombolytic therapy. 1

What is the NIHSS?

The NIHSS is a standardized, validated instrument that:

• Assesses severity of neurological impairment after stroke
• Contains 11 items examining different neurological functions
• Ranges from 0 to 42 points (higher scores indicate greater impairment)
• Takes only 5-10 minutes to administer
• Can be performed by any trained clinician 1

Clinical Significance of NIHSS Scores

Outcome Prediction

• Score <6: Forecasts good recovery
• Score >16: Forecasts high probability of death or severe disability 1
• Score ≤7: Associated with only 14.8% risk of early neurological worsening
• Score >7: Associated with 65.9% risk of early neurological worsening 2

Treatment Decision-Making

• Guides decisions about acute stroke therapy, particularly thrombolytic treatment
• Influences patient selection for specific interventions
• Helps stratify patients according to severity and likely outcome 1

Implementation in Clinical Practice

When to Perform NIHSS Assessment

1. At the time of presentation/hospital admission (within first 24 hours)
2. Before diagnostic cerebral angiography (if applicable)
3. At the time of acute care discharge
4. Upon transfer to rehabilitation if previous scores are not available 1

Who Should Perform NIHSS

• All professionals involved in stroke care should be trained and certified
• Certification involves watching training videos and passing an examination
• Inter-rater reliability between examiners is high for most items 1

Special Considerations and Limitations

Posterior Circulation Strokes

• NIHSS may underestimate severity of posterior circulation strokes
• Patients with posterior circulation strokes often present with lower NIHSS scores (median 2 vs. 7 for anterior circulation)
• Lower cutoff values are needed for posterior circulation strokes:
  • Optimal cutoff for outcome prediction: 4 for posterior vs. 8 for anterior circulation
  • For >80% sensitivity in detecting poor outcomes: 2 for posterior vs. 4 for anterior circulation 3
• 15% of patients with "minor" posterior circulation strokes (NIHSS ≤4) still have poor outcomes at 3 months 3

Clinical Profiles Beyond Total Score

• Patients with identical NIHSS scores may have different outcomes based on the pattern of deficits
• Patients with decreased level of consciousness and language deficits may have worse outcomes than those with equivalent motor deficits 4

Practical Application in Emergency Settings

Integration into Stroke Protocols

• NIHSS should be part of organized protocols for emergency evaluation
• Goal: Complete evaluation and treatment decisions within 60 minutes of arrival
• For potential thrombolytic candidates, CT should be completed within 25 minutes and interpreted within 45 minutes of arrival 1

Hospital Requirements

• Hospitals must provide necessary resources to implement NIHSS
• All stroke team members should be trained in NIHSS assessment
• Documentation of scores should be standardized 1

Common Pitfalls to Avoid

1. Underestimating posterior circulation strokes: Don't withhold treatment based solely on low NIHSS scores in suspected posterior circulation strokes 3

2. Relying only on total score: Consider the pattern of deficits, as different symptom profiles with identical scores may have different outcomes 4

3. Incomplete assessment: The original NIHSS doesn't test distal upper extremity weakness, which is common in stroke patients - consider adding finger extension assessment 1

4. Delayed reassessment: Second assessments serve as important rechecks and may be more accurate as patients stabilize 1

The NIHSS has become an indispensable tool in acute stroke management, providing critical information for treatment decisions and outcome predictions that directly impact patient morbidity, mortality, and quality of life.