Hunt and Hess Classification

Why use it

The Hunt and Hess grade at admission is one of the strongest independent predictors of outcome after aneurysmal SAH. It guides clinical decision-making including timing of surgical clipping or endovascular coiling, ICU admission intensity, and family counseling about prognosis. Higher grades require intensive neurological monitoring and may require stabilization before definitive aneurysm treatment.

About

The Hunt and Hess Classification is the most widely used clinical grading system for aneurysmal subarachnoid hemorrhage (SAH). Developed by William Hunt and Robert Hess in 1968, it stratifies patients into five grades (I–V) based on the severity of neurological presentation at admission. The grade strongly correlates with operative risk, neurological outcome, and mortality. Grade I represents asymptomatic or minimal headache; Grade V represents deep coma with decerebrate posturing. The scale was originally designed to guide surgical timing — lower grades were considered favorable for early surgery, while higher grades prompted delayed surgery after neurological optimization. The Hunt and Hess scale remains the most widely applied SAH grading system in clinical practice, used alongside the World Federation of Neurological Surgeons (WFNS) scale and the Modified Fisher scale (radiographic severity).

When to use

• At admission for any confirmed or suspected aneurysmal subarachnoid hemorrhage
• Before surgical clipping or endovascular coiling to assess procedural risk
• For prognostication and family counseling regarding expected functional outcomes
• Serial assessment during clinical course to detect neurological deterioration or improvement
• Research enrollment and clinical trial stratification for SAH studies

Formula

Pearls & pitfalls

• Grade I patients have an excellent prognosis if the aneurysm is secured early — do not delay intervention in Grade I or II patients without compelling reason.
• The Hunt and Hess scale can be confounded by sedation, metabolic encephalopathy, or hydrocephalus — always assess before any sedation if possible, and re-grade after EVD placement.
• Grade V carries >80–100% mortality — goals-of-care discussion with family is mandatory before invasive intervention is pursued.
• WFNS correlation: HH Grade I ≈ WFNS I; HH II ≈ WFNS II; HH III ≈ WFNS III; HH IV ≈ WFNS IV; HH V ≈ WFNS V.
• Serious systemic comorbidities (hypertension, diabetes, severe atherosclerosis, COPD) may shift the effective operative risk upward in the modified Hunt and Hess classification.
• Grade III patients with acute hydrocephalus may improve dramatically after external ventricular drain (EVD) placement — re-assess grade after CSF drainage before finalizing management plan.
• The Hunt and Hess scale does not incorporate neuroimaging — always correlate with Modified Fisher grade (CT head) for complete risk stratification.
• Nimodipine 60 mg orally or via NGT every 4 hours for 21 days is standard for ALL grades of aneurysmal SAH — it reduces vasospasm-related ischaemia regardless of grade.

Next steps

Grade I–II: Favorable — early surgical or endovascular intervention recommended. Transfer to neurosurgical centre if not available. ICU admission. Nimodipine 60 mg every 4h × 21 days for vasospasm prevention. Grade III: Moderate risk — intervention when neurologically stable or improving. Treat reversible causes of encephalopathy (hydrocephalus, hyponatremia). Grade IV–V: High/very high risk — stabilize first; consider delayed intervention after neurological improvement. Goals-of-care discussion with family is essential. All grades: nimodipine, euvolemia, avoidance of hypotension, monitoring for vasospasm (Day 4–14), hydrocephalus, and rebleeding.

Evidence

Hunt WE, Hess RM. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg. 1968;28(1):14-20. PMID:5635959. The scale has been validated in numerous studies correlating grade with surgical outcome, mortality, and long-term functional status. 30-day mortality by grade: Grade I <5%, Grade II 2–10%, Grade III 10–15%, Grade IV 60–70%, Grade V 70–100%. Rosen DS, Macdonald RL. Neurocrit Care. 2005 validated concordance with WFNS scale and confirmed strong prognostic value.

References

1. Hunt WE, Hess RM. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg. 1968;28(1):14-20. — link
2. Rosen DS, Macdonald RL. Subarachnoid hemorrhage grading scales: a systematic review. Neurocrit Care. 2005;2(2):110-118. — link
3. Connolly ES et al. Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage. Stroke. 2012;43(6):1711-1737. — link