Role of the NIH Stroke Scale in Stroke Assessment and Management
The NIH Stroke Scale (NIHSS) is a critical standardized assessment tool that should be used to evaluate all stroke patients at presentation, within 24 hours of admission, and at discharge to guide treatment decisions and predict outcomes. 1
Key Components and Administration
- The NIHSS is a standardized, validated instrument specifically designed to assess the severity of neurological impairment after stroke, with scores ranging from 0 to 42 (higher scores indicating more severe strokes) 1, 2
- The scale consists of 11 original items and takes only 5-10 minutes to administer, making it efficient for emergency settings 1
- The NIHSS is based solely on examination and requires no historical information or contributions from surrogates, allowing for objective assessment 1
- An additional item examining finger extension is often added to the NIHSS to assess distal upper extremity weakness, which is more common than proximal arm weakness in stroke patients 1
- The scale can be administered by any trained clinician (physician, nurse, therapist, or social worker) who has been properly certified 1
Clinical Applications and Timing
The NIHSS should be performed at three critical timepoints 1:
- At the time of presentation/hospital admission or within the first 24 hours
- At the time of acute care discharge
- Upon transfer to rehabilitation if previous scores are not available
The scale is particularly valuable in guiding decisions about acute stroke therapy, including the use of thrombolytic therapy 1
Inter-rater reliability between examiners for most items of the NIHSS is high, making the scale highly reproducible across different healthcare settings 1
Prognostic Value
The NIHSS strongly predicts patient outcomes after stroke 1, 3:
- A score greater than 16 forecasts a high probability of death or severe disability
- A score less than 6 forecasts a good recovery
- During the first week after acute ischemic stroke, the NIHSS can identify patients likely to have poor outcomes
Different stroke types may require different NIHSS thresholds for prognosis 4:
- For anterior circulation strokes, an NIHSS cutoff of 8 best predicts outcomes
- For posterior circulation strokes, a lower NIHSS cutoff of 4 best predicts outcomes
- This difference is critical as posterior circulation strokes often present with lower NIHSS scores but may still have poor outcomes
Implementation Requirements
- All professionals involved in any aspect of stroke care should be trained and certified to assess stroke severity using the NIHSS 1
- Certification is achieved by watching a training videotape and passing an examination that involves scoring patients shown on a test tape 1
- Ongoing validation of the predictive value of the NIHSS through prospective data collection is encouraged to maintain and improve its clinical utility 1
Clinical Pearls and Pitfalls
- Posterior circulation strokes often present with lower NIHSS scores, which may result in withholding thrombolytic treatment; however, these patients can still have poor outcomes and should not be denied treatment based solely on low NIHSS scores 4
- When assessing motor function, it's important to distinguish between no effort against gravity (score of 3) and no movement at all (score of 4) 2
- For language assessment, even subtle hesitations or circumlocutions may indicate mild aphasia rather than normal language function 5
- Serial assessments using the NIHSS can track recovery patterns, with different stroke subtypes showing different improvement trajectories 6