What is the role of the National Institutes of Health Stroke Scale (NIHSS) in guiding treatment for acute ischemic stroke?

Role of the National Institutes of Health Stroke Scale (NIHSS) in Guiding Treatment for Acute Ischemic Stroke

The NIHSS is a critical standardized assessment tool that should be administered to all acute stroke patients at presentation to guide treatment decisions, predict outcomes, and stratify stroke severity, with scores >16 indicating high mortality risk and scores <6 predicting good recovery. 1

Purpose and Administration of NIHSS

The NIHSS is a 15-item neurological examination scale designed to:

• Quantify stroke severity (scores range from 0-42, higher scores indicate greater severity)
• Guide acute treatment decisions, particularly regarding thrombolytic therapy
• Predict patient outcomes and mortality risk
• Standardize neurological assessment across providers

When to Administer NIHSS:

• At time of presentation/hospital admission (or within first 24 hours)
• At acute care discharge
• Upon transfer to rehabilitation if no prior scores exist 2, 1

NIHSS and Treatment Decision-Making

Thrombolytic Therapy Decisions

• Risk stratification: NIHSS helps identify patients at higher risk for hemorrhagic complications with thrombolytic therapy
• Patients with NIHSS scores ≥20 have a 17% risk of intracranial hemorrhage with rtPA
• Patients with NIHSS scores <10 have only a 3% risk of bleeding with rtPA 2

Prognostic Value

• NIHSS <10: 60-70% of patients will have favorable outcomes at 1 year
• NIHSS >20: Only 4-16% of patients will have favorable outcomes at 1 year 2
• NIHSS >16: Forecasts high probability of death or severe disability
• NIHSS <6: Forecasts good recovery 2, 1

Mortality Prediction

• Strong association between baseline NIHSS score and mortality
• Can be categorized as:
  • Good (0-6 points): Lower mortality risk
  • Moderate (7-15 points): Intermediate mortality risk
  • Poor (≥16 points): Highest mortality risk 3

Limitations and Special Considerations

Anterior vs. Posterior Circulation

• NIHSS was primarily designed for anterior circulation strokes and may underestimate posterior circulation stroke severity 1, 4
• Posterior circulation strokes often receive lower NIHSS scores despite potentially serious outcomes 5, 4
• A cutoff of NIHSS 4 is optimal for predicting outcomes in posterior circulation strokes, while for anterior circulation strokes it is 8 1

Documentation Considerations

• Only current stroke-related deficits should be included in scoring
• Prior deficits should be documented separately to avoid inappropriate treatment decisions 1

Implementation in Clinical Practice

Training and Certification

• All professionals involved in stroke care should be trained and certified in NIHSS assessment 2, 1
• Certified examiners can be from any background (physicians, nurses, therapists) 2
• Inter-rater reliability between examiners for most NIHSS items is high 2

Integration into Workflow

• Successful implementation requires staff education and integration into clinical workflows
• Use of pocket cards and emphasis during interdisciplinary rounds can improve compliance 6

Common Pitfalls to Avoid

• Including prior deficits in scoring (should document separately)
• Underestimating posterior circulation strokes due to NIHSS limitations
• Failing to reassess NIHSS at critical timepoints (admission, discharge, transfer)
• Using untrained personnel to administer the scale
• Relying solely on NIHSS without considering other clinical factors

The NIHSS provides essential information for treatment decisions in acute stroke care, helping clinicians determine appropriate interventions to reduce mortality and improve outcomes. Its standardized approach ensures consistent assessment across providers and settings.