WFNS Score
The World Federation of Neurological Surgeons (WFNS) grading scale is a Class I, Level B-NR recommended clinical tool for determining initial severity and predicting outcome in aneurysmal subarachnoid hemorrhage (aSAH), with grades 4-5 defining high-grade SAH that requires individualized treatment decisions based on presence of irrecoverable brain injury 1.
What the WFNS Scale Is
The WFNS scale is a clinical grading system that stratifies aSAH patients from Grade I (best) to Grade V (worst) based on:
- Glasgow Coma Scale (GCS) score
- Presence or absence of motor deficits
This scale serves as both a prognostic indicator and a standardization tool for hemorrhage severity 1.
Clinical Significance and Outcome Prediction
High-grade SAH is defined as WFNS Grade 4-5, which carries significant mortality and morbidity risk. However, outcomes are not uniformly poor:
- Approximately 39-40% of treated high-grade patients achieve good outcomes at 12 months 1
- The scale's predictive accuracy varies significantly based on timing of assessment
Critical Timing Considerations
The WFNS grade assessed at 48 hours post-aneurysm occlusion provides superior prognostic accuracy compared to admission grading 2:
- 48-hour assessment achieves AUC of 0.817-0.845 for discharge outcomes
- This timing reflects stabilized neurological status after resolution of confounding factors
- Admission grading may misclassify "false poor grade" patients who improve within days
The worst pretreatment WFNS grade is the single best predictor when early assessment is required 3. Patients with GCS 13 have substantially worse outcomes than those with GCS 14, supporting the modified WFNS scale that separates these groups 4.
Treatment Decision Algorithm
For WFNS Grade 1-3 (Low-to-Moderate Grade):
- Proceed with aneurysm treatment (endovascular coiling or surgical clipping) to prevent rebleeding
- Management in specialized neuro-ICU with multidisciplinary teams 1
For WFNS Grade 4-5 (High-Grade):
Assess for irrecoverable brain injury markers 1:
- Absent or partially absent brainstem reflexes (especially if persistent at 12-24 hours)
- Lack of purposeful response to noxious stimuli
- Large completed ischemic infarct on admission CT
- Global cerebral edema consistent with anoxic injury
If irrecoverable injury present: Aneurysm treatment provides no benefit; focus on comfort measures
If NO irrecoverable injury:
Identify and correct modifiable conditions first:
- Seizures or status epilepticus
- Hydrocephalus requiring drainage
- Severe electrolyte abnormalities (hyponatremia)
- Hypothermia
Reassess WFNS grade after correction - many "false poor grade" patients improve 5, 6
Consider aneurysm treatment with shared decision-making involving family/surrogates 1
Factor in age: Patients >65 years have lower functional independence rates (42% vs 82% in younger patients at 6 years), but treatment remains reasonable after family discussion 1
Key Pitfalls to Avoid
- Don't grade too early: Admission WFNS may misclassify patients due to sedation, intubation, or reversible factors 2, 5
- Don't assume all Grade 4-5 patients have poor prognosis: 40% achieve favorable outcomes with treatment 1
- Don't miss modifiable causes of poor grade: Hydrocephalus, seizures, and metabolic derangements can falsely elevate the grade 1, 6
- Don't use timing of grading inconsistently: Standardize whether using admission, worst pretreatment, or 48-hour post-treatment assessment 3
Practical Application
For prognostication: Use 48-hour post-occlusion WFNS grade when possible for most accurate outcome prediction 2
For acute treatment decisions: Use worst pretreatment WFNS grade, but reassess after correcting modifiable factors 3, 6
For research/quality metrics: Specify timing of WFNS assessment, as this significantly impacts interpretation 2, 3
The WFNS scale remains superior to Hunt-Hess for outcome prediction when properly timed, and outperforms composite scores for clinical decision-making in most scenarios 3, 7.