Clinical Features of Subarachnoid Hemorrhage
The classic presentation of subarachnoid hemorrhage is sudden-onset severe headache reaching maximum intensity within 1 hour (thunderclap headache), often described as "worst headache of life," accompanied by neck pain/stiffness, altered consciousness, and onset during exertion 1, 2.
Primary Clinical Presentations
Cardinal Symptom: Headache
- Thunderclap headache (instantly peaking pain) is the hallmark feature 1
- Reaches maximum intensity within 1 hour 1
- Present in approximately 70% of cases 3
- Critical caveat: Less than half of patients present with the complete classic syndrome 4. Atypical presentations include:
- Gradual evolution of symptoms
- Non-intense headaches
- Minimal or no headache (9 patients in one series with preserved consciousness) 4
Associated Symptoms (in order of frequency)
- Vomiting (61% of cases) 3
- Loss of consciousness (witnessed in 28% of cases) 1, 3
- Neck pain or stiffness (key diagnostic feature) 1
- Giddiness/dizziness (30%) 3
- Syncope (26%) 3
- Seizures (20%) 3
- Confusion and vegetative symptoms 5
Physical Examination Findings
Common Signs
- Elevated blood pressure (34% at presentation) 3
- Neck stiffness/meningeal signs (21% at ED presentation—often absent initially) 3
- Focal neurological deficits (13%), indicating intraparenchymal hemorrhage 3
- Cranial nerve palsies (can indicate aneurysm location and increased intracranial pressure) 5
- Terson's syndrome (vitreous hemorrhage—indicates poor prognosis) 5
- Fever (8%) 3
- Preretinal hemorrhages (2%) 3
Ottawa SAH Rule Criteria (Screening Tool)
For alert patients >15 years with new severe non-traumatic headache reaching maximum intensity within 1 hour, additional investigation is required if ANY of the following are present 1:
- Age ≥40 years
- Neck pain or stiffness
- Witnessed loss of consciousness
- Onset during exertion
- Thunderclap headache (instantly peaking pain)
- Limited neck flexion on examination
This rule is 100% sensitive but only 7.6-15.3% specific, meaning it identifies a small subset who can safely avoid further workup 1.
Sentinel Bleeds (Warning Leaks)
Approximately 50% of patients experience "sentinel headaches" days to weeks before catastrophic rupture 6. Recognition at this stage permits treatment before devastating neurologic events and can be lifesaving 1.
Atypical Presentations Requiring High Clinical Suspicion
Important pitfall: Many patients present atypically, leading to 19% delayed diagnosis rates 4. Watch for:
- Primary neck pain without severe headache 1
- Syncope as sole presentation 1
- Seizure 1
- New focal neurological deficit 1
- Transient neurological symptoms without relevant headache (particularly in elderly patients) 5
- Severe pain at sites other than head 4
- Disturbed consciousness with mild meningeal signs 4
Severity Assessment
Clinical severity correlates directly with prognosis 5. The extent of confusion and altered consciousness correlates with disease severity and remains the primary prognostic indicator, as originally described by Hunt and Hess in 1968, now often combined with Glasgow Coma Scale 5.
Critical Clinical Context
Mortality reaches 50% 2, making rapid recognition essential. Approximately 80% of non-traumatic SAH cases are due to aneurysmal rupture 2. The combination of severe acute headache, neck stiffness, and altered consciousness should trigger immediate imaging, though the absence of neck stiffness at initial ED presentation is common and should not exclude the diagnosis 3.