Hunt and Hess and Modified Fischer Scales in Subarachnoid Hemorrhage Assessment
The Hunt and Hess scale is a clinical grading system that assesses neurological severity in subarachnoid hemorrhage patients based on symptoms and level of consciousness, while the modified Fischer scale (Fisher scale) is a CT-based radiographic grading system that evaluates the amount and distribution of blood to predict vasospasm risk. 1
Hunt and Hess Scale - Clinical Assessment
The Hunt and Hess scale divides patients into 5 grades of progressively increasing severity based on clinical presentation 1:
- Grade 1: Asymptomatic or mild headache 1
- Grade 1a: Fixed neurological deficit without meningeal or brain reaction 1
- Grade 2: Moderate to severe headache, cranial nerve palsy, nuchal rigidity 1
- Grade 3: Lethargy, confusion, mild focal deficit 1
- Grade 4: Stupor, hemiparesis, early decerebrate posturing 1
- Grade 5: Coma, decerebrate posturing, moribund appearance 1
The severity determined by Hunt and Hess grading is the most useful indicator of outcome after aneurysmal SAH and should be determined rapidly to guide treatment decisions and prognostication. 1
Clinical Application
- Hunt and Hess grades 1-2 are considered low-grade SAH, while grades 3-5 are high-grade 2
- High-grade patients (Hunt and Hess 4-5) historically had poor outcomes, but recent data shows 39-40% can achieve favorable outcomes with aggressive early treatment 1
- The scale guides urgent treatment decisions, as patients with higher grades require more intensive monitoring and earlier aneurysm securing 1
Fisher Scale - Radiographic Assessment
The Fisher Grading Scale is a CT-based system with prognostic significance for development of vasospasm and delayed ischemic neurological deficits 1:
- Fisher Group 1: No subarachnoid blood detected 1
- Fisher Group 2: Diffuse or vertical layer of blood less than 1mm thick 1
- Fisher Group 3: Localized clot and/or vertical layer of blood 1mm or greater in thickness 1
- Fisher Group 4: Diffuse or no subarachnoid blood, but with intracerebral or intraventricular clots 1
The Fisher scale predicts vasospasm risk, with Fisher grade 3 having the highest association with symptomatic vasospasm. 1
Modified Fisher Scale
The modified Fisher scale (also called Fisher revised scale) provides improved prognostic accuracy 3:
- Patients classified as modified Fisher grade 4 had the highest rate (63.63%) of delayed neurological deficit from vasospasm 3
- This revised scale better stratifies patients for vasospasm monitoring intensity 3
Recommended Use in Clinical Practice
Guidelines recommend using validated scales including Hunt and Hess, World Federation of Neurological Surgeons (WFNS), Glasgow Coma Scale (GCS), and Fisher Scale to determine SAH severity. 1
Key Clinical Decisions Guided by These Scales
- Timing of aneurysm treatment: High Hunt and Hess grades require urgent securing of aneurysm within 24-48 hours to prevent rebleeding 1
- Vasospasm monitoring: Higher Fisher grades necessitate more intensive transcranial Doppler monitoring and consideration of prophylactic nimodipine 1, 3
- Prognostication: Combined clinical (Hunt and Hess) and radiographic (Fisher) grading provides comprehensive outcome prediction 1
- Treatment intensity: Hunt and Hess grade 4-5 patients require careful consideration for aggressive treatment versus comfort measures, though recent evidence supports treatment in selected cases 1, 4
Important Caveats
- The Hunt and Hess scale has some subjectivity in grade 3 assessment (lethargy vs confusion), which can affect interrater reliability 5, 6
- Fisher grade alone does not capture clinical severity—both clinical and radiographic scales should be used together 1
- Do not confuse these scales with traumatic SAH assessment, which requires different management approaches focused on intracranial pressure monitoring rather than aneurysm treatment 7
- The scales should be applied at admission and serially reassessed, as clinical deterioration may occur from rebleeding, hydrocephalus, or vasospasm 1