What are the grades of the Hunt and Hess scale for aneurysmal subarachnoid hemorrhage and the associated management and prognosis?

Hunt and Hess Scale for Aneurysmal Subarachnoid Hemorrhage

The Hunt and Hess (HH) scale is a Class 1, Level B-NR recommended clinical grading system for determining initial severity and predicting outcomes in aneurysmal subarachnoid hemorrhage (aSAH), with grades 4 and 5 defining poor-grade SAH that still warrants aggressive treatment in approximately 40% of cases who can achieve favorable outcomes. 1

The Five Grades

The HH scale stratifies patients into five grades based on clinical presentation:

• Grade 1: Asymptomatic or minimal headache with slight nuchal rigidity
• Grade 2: Moderate to severe headache, nuchal rigidity, cranial nerve palsy possible
• Grade 3: Drowsiness, confusion, or mild focal neurological deficit
• Grade 4: Stupor, moderate to severe hemiparesis, early decerebrate rigidity
• Grade 5: Deep coma, decerebrate rigidity, moribund appearance

Prognostic Significance

High-grade SAH (HH 4-5) carries significant mortality but treatment can yield favorable outcomes (modified Rankin Scale 0-2) in 39-40% of treated patients at 12 months. 1 This represents a dramatic improvement from the pre-coiling era when HH grade 5 patients had 0% favorable outcomes and 94% 6-month mortality 2.

Critical Timing Consideration

Reassess the HH grade at 48 hours post-admission—this delayed assessment significantly improves prognostic accuracy compared to admission grading alone. 3 Early neurological changes occur in 24% of patients between hospital days 1-3, and each point change in HH grade substantially alters outcome prediction (OR 2.57 for deterioration, OR 0.28 for improvement) 4.

Management Algorithm

Immediate Actions (Within 24 Hours)

Secure the aneurysm within 24 hours of ictus when the most experienced team is available—early treatment reduces rebleeding risk and facilitates delayed cerebral ischemia management. 1, 5

For HH grades 1-3:

• Proceed directly to aneurysm treatment (coiling preferred over clipping for suitable aneurysms)
• Initiate oral nimodipine 60mg every 4 hours
• Transfer to specialized neurointensive care unit treating ≥70 aSAH cases annually 5

For HH grades 4-5:

• First, identify and correct reversible causes before declaring futility: seizures, hydrocephalus, hyponatremia, status epilepticus, hypothermia 1
• Reassess neurological exam at 12-24 hours—absent brainstem reflexes at presentation carry different weight than those persisting at 24 hours 1
• If reversible causes corrected and some brainstem function present, proceed to aneurysm treatment
• Bilateral intact corneal reflexes and younger age are independent predictors of favorable outcome 2

Treatment Contraindications in HH Grade 5

Do not treat if the following features of irrecoverable brain injury are present:

• Completely absent brainstem reflexes persisting beyond 24 hours
• Lack of purposeful responses to noxious stimuli after correcting reversible causes
• Large completed ischemic infarct on admission CT
• Global cerebral edema consistent with anoxic brain injury 1

Post-Treatment Management

Implement bundled treatment protocols—these improve 6-month favorable outcomes from 21% to 46% and reduce mortality from 27% to 14% in poor-grade aSAH. 6 This includes:

• Multimodal neuromonitoring in dedicated neuro-ICU
• Aggressive management of cerebral edema, elevated ICP, and hydrocephalus
• Surveillance for delayed cerebral ischemia (occurs in up to 65% of treated HH grade 5 patients) 2
• Continuation of nimodipine for 21 days
• Early enteral nutrition and mobilization when feasible 7

Age Considerations

Age significantly impacts outcomes but does not preclude treatment. In patients >65 years with aSAH, 42% achieve functional independence at 6 years compared to 82% in younger patients—this justifies treatment after shared decision-making with family 1. The number needed to treat for favorable outcome in poor-grade aSAH is 3, which compares favorably to decompressive craniectomy for MCA infarction (NNT=7) 2.

Critical Pitfall

Never use initial admission HH grade alone for prognostication or treatment decisions in grades 4-5—wait 48-72 hours while aggressively treating reversible causes. The clinical trajectory during this window provides substantially more accurate outcome prediction than admission status 3, 4. Premature withdrawal of care based on admission grade alone denies potentially salvageable patients the 40% chance of favorable outcome that aggressive treatment provides.