Prognostic Tools for Aneurysmal Subarachnoid Hemorrhage
Use the Hunt and Hess (HH) grade or World Federation of Neurosurgical Societies (WFNS) grade immediately upon presentation to determine initial clinical severity and predict mortality and functional outcome. 1
Primary Clinical Grading Scales
Hunt and Hess Classification
The HH grade is the most strongly recommended clinical scale for initial prognostication, with the following grades 2:
- Grade 0: Unruptured aneurysm
- Grade 1: Asymptomatic or mild headache
- Grade 1a: Fixed neurological deficit without meningeal or brain reaction
- Grade 2: Moderate to severe headache, cranial nerve palsy, nuchal rigidity
- Grade 3: Lethargy, confusion, mild focal deficit
- Grade 4: Stupor, hemiparesis, early decerebrate posturing
- Grade 5: Coma, decerebrate posturing, moribund appearance
Higher HH grades (4-5) predict acute hydrocephalus, intraventricular blood, and need for ventricular drainage, though 30-40% of these poor-grade patients can still achieve good outcomes with aggressive treatment 1, 2.
World Federation of Neurosurgical Societies (WFNS) Grade
The WFNS scale is equally recommended as an alternative to HH grading, with comparable predictive accuracy for mortality and functional outcomes 1.
Composite Prognostic Scores
SAHIT Score (Subarachnoid Hemorrhage International Trialists)
The SAHIT score was developed and validated on 14,291 patients and identifies age, premorbid hypertension, and neurological grade as key predictors of outcome 1. CT clot thickness, aneurysm size/location, and treatment method add only marginal predictive value 1.
Composite Radiographic-Clinical Scores
Recent combination scores provide enhanced prognostication 1:
- VASOGRADE: Combines clinical and radiographic grades
- HAIR score: Incorporates HH grade, age, intraventricular hemorrhage (IVH), and rebleed
- SAH score: Integrates multiple clinical and radiographic factors
These composite scores assist in standardizing hemorrhage severity and predicting clinical outcomes 1.
Key Prognostic Factors Beyond Grading Scales
Age
Age ≥65-70 years is an independent predictor of poor outcome 1, 3, 4. In the Barrow Ruptured Aneurysm Trial, only 42% of patients >65 years achieved functional independence at 6 years, compared to 82% of younger patients 1. However, treatment should still be considered after discussion with family, as outcomes can be favorable 1.
Radiographic Factors
- Modified Fisher grade >2 predicts poor prognosis (OR 2.972) 3
- SAH thickness ≥10 mm independently predicts unfavorable outcomes 4
- Fisher Grade 3 (thick subarachnoid blood) carries highest risk of symptomatic vasospasm 5
Treatment-Related Factors
- Conservative (non-interventional) treatment strongly predicts poor outcome (OR 5.078) 3
- Delayed cerebral ischemia (DCI) is an independent predictor of poor prognosis (OR 3.170) 3
- Shunt-dependent hydrocephalus predicts unfavorable outcomes (OR 3.202) 3
- Cerebral herniation is the strongest predictor of mortality (OR 7.337) 3
Practical Prognostic Models
Poor-Grade aSAH Scoring Model (WFNS IV-V)
A validated scoring system (0-9 points) stratifies poor-grade patients into risk categories 3:
- Low risk (0-1 points): 11% predicted poor outcome
- Intermediate risk (2-3 points): 52% predicted poor outcome
- High risk (4-9 points): 87% predicted poor outcome
Points are assigned for: modified Fisher >2, age ≥65, conservative treatment, WFNS V, DCI, shunt-dependent hydrocephalus, and cerebral herniation 3.
eSAH Score
A simple quantitative model using age, Glasgow Coma Scale score, and SAH volume measured on CT predicts mortality (AUC 0.88), DCI (AUC 0.75), and functional outcomes (AUC 0.89) 6.
Discharge Outcome Prediction Scale
A 0-5 point scale assigns 4:
- 2 points: Post-resuscitation GCS ≤8
- 1 point each: Age ≥70 years, antiplatelet therapy on admission, SAH thickness ≥10 mm
This scale achieved AUC 85.2% for predicting discharge mortality and functional outcomes 4.
Critical Pitfalls to Avoid
Do not use grading scales alone to withhold treatment in high-grade patients (HH 4-5 or WFNS 4-5), as 39-40% achieve good outcomes with aggressive multidisciplinary care 1, 5.
Exclude patients from treatment only if they have irrecoverable brain injury: partially/completely absent brainstem reflexes persisting beyond 12-24 hours, lack of purposeful responses to noxious stimuli, large completed ischemic infarct on admission CT, or global cerebral edema consistent with anoxic brain injury 1.
Identify and correct modifiable conditions before prognostication: seizures, hydrocephalus, electrolyte abnormalities (especially hyponatremia), status epilepticus, and hypothermia significantly affect outcomes and must be addressed first 1.
Timing matters for prognostication: Absent brainstem responses at presentation carry different implications than absent responses at 12-24 hours; early CT may not reveal brain edema that becomes apparent later 1.
Comparative Performance of Grading Systems
The HH, WFNS, and SAHIT scales demonstrate similar discriminative ability (AUROCs 0.80-0.85) and outperform the modified Fisher scale (AUROC 0.61) for predicting functional outcomes 4, 7. However, no single instrument consistently outperforms others across all age groups and severity levels 7.
The HATCH score (Hemorrhage, Age, Treatment, Clinical Status, Hydrocephalus) achieved AUROC 0.83 for unfavorable outcomes but did not outperform non-specific critical care scores like APACHE II (AUROC 0.84) or SOFA (AUROC 0.83) 8.