What are the presenting symptoms of a cerebral aneurysm and the urgent diagnostic steps?

Cerebral Aneurysm Symptoms and Urgent Diagnostic Approach

Clinical Presentation

Cerebral aneurysms present in two distinct patterns: ruptured aneurysms causing subarachnoid hemorrhage (the most critical presentation) and unruptured aneurysms (often incidental or causing focal symptoms).

Ruptured Aneurysm Presentation (Subarachnoid Hemorrhage)

The classic presentation of aneurysmal rupture is sudden-onset severe headache ("thunderclap" or "worst headache of my life"), reported by 80% of patients who can provide history. 1

• Typical symptoms include: severe headache reaching maximum intensity within 1 hour, nausea, vomiting, photophobia, and nuchal rigidity 2
• Common signs include: altered level of consciousness, focal weakness, and cranial nerve deficits 2
• Critical red flags requiring immediate workup: sudden onset headache, associated neck pain or stiffness, witnessed loss of consciousness, age ≥40 years, focal neurological deficits or cranial nerve palsies, and altered mental status 3

Warning (Sentinel) Headaches

Sentinel headaches occur in 10-43% of patients within 2-8 weeks before major rupture, and recognizing these can be lifesaving. 3, 1

• These represent minor leaks or aneurysm expansion and indicate imminent rupture risk 4
• Dismissing warning headaches increases the odds of early rebleeding 10-fold 1
• Even "thunderclap" headaches without confirmed subarachnoid hemorrhage on initial imaging may indicate aneurysm expansion and warrant urgent neurovascular imaging 4

Unruptured Aneurysm Presentation

Most unruptured intracranial aneurysms are asymptomatic or present with vague, non-specific symptoms like headache or dizziness. 5

• Isolated oculomotor nerve palsy (third nerve palsy) typically indicates a posterior circulation aneurysm, particularly posterior communicating artery aneurysm 5
• Sudden onset of third nerve palsy suggests aneurysm expansion and concern for imminent rupture, necessitating rapid workup and intervention 2
• Incidental aneurysms are discovered during imaging for clearly unrelated causes (head trauma, spine evaluation, migraine, tension headaches, seizures, or neoplasm staging) 2

Urgent Diagnostic Algorithm

Step 1: Immediate Imaging (Within Minutes of Presentation)

Obtain non-contrast head CT immediately—it has 98-100% sensitivity in the first 12 hours after hemorrhage. 3, 1

• CT sensitivity decreases with time, making early imaging critical 3
• Failure to obtain neuroimaging is the most common diagnostic error, occurring in up to 12% of misdiagnosed cases 1
• Misdiagnosis carries nearly 4-fold higher mortality and disability 3, 1

Step 2: Lumbar Puncture (If CT Negative but Suspicion High)

If CT is negative but clinical suspicion remains high, perform lumbar puncture to evaluate for xanthochromia, which has 100% sensitivity and 95.2% specificity. 3

• Xanthochromia (yellow discoloration of CSF from hemoglobin breakdown) confirms subarachnoid hemorrhage even when CT is negative 3
• This step is mandatory when red flags are present despite negative CT 3, 1

Step 3: Vascular Imaging to Identify the Aneurysm

Once subarachnoid hemorrhage is confirmed, perform CT angiography (CTA) immediately—it has 96.5-97.2% sensitivity and 88-97.9% specificity for detecting aneurysms. 3

• CTA with modern multidetector scanners has very high accuracy compared to digital subtraction angiography (DSA), with sensitivity of 96.3%, specificity of 100%, and accuracy of 94.6% 2
• However, sensitivity is lower for aneurysms <3 mm (81.8%) 2

Digital subtraction angiography (DSA) with 3D rotational angiography remains the gold standard and is indicated when CTA is negative or inconclusive but SAH is confirmed, or for treatment planning. 3

• DSA has >98% sensitivity and specificity for detecting aneurysms 3
• DSA provides the highest spatial resolution for evaluating dome-to-neck ratio, neck-to-artery ratio, and exact aneurysm dimensions for treatment planning 2
• Permanent neurological complications from diagnostic DSA occur at a rate of only 0.07% 2

Step 4: Clinical Severity Grading

Rapidly assess clinical severity using the Hunt and Hess Scale or World Federation of Neurological Surgeons (WFNS) Scale. 2, 3, 6

Hunt and Hess Grading Scale: 2, 6

• Grade 0: Unruptured aneurysm

• Grade 1: Asymptomatic or mild headache (GCS 15)

• Grade 1a: Fixed neurological deficit without meningeal or brain reaction

• Grade 2: Moderate to severe headache, cranial nerve palsy, nuchal rigidity (GCS 13-14 without motor deficit)

• Grade 3: Lethargy, confusion, mild focal deficit (GCS 13-14 with motor deficit)

• Grade 4: Stupor, hemiparesis, early decerebrate posturing (GCS 7-12)

• Grade 5: Coma, decerebrate posturing, moribund appearance (GCS 3-6)

• Higher Hunt and Hess grades independently predict acute hydrocephalus, intraventricular blood, and need for ventricular drainage 6

• Initial Hunt and Hess grade is the strongest predictor of outcome after aneurysmal SAH 6

Immediate Management Actions After Diagnosis

Once aneurysmal subarachnoid hemorrhage is diagnosed, initiate the following urgent interventions: 3, 1, 6

1. Transfer to a high-volume center (>35 aSAH cases/year) with neurosurgical and endovascular capabilities 3, 1
2. Control blood pressure: Maintain systolic BP <160 mmHg using titratable intravenous agents to balance rebleeding risk against cerebral perfusion 3, 1, 6
3. Administer oral nimodipine 60 mg every 4 hours if presenting within 96 hours and adequate blood pressure—this is the only Class I, Level A recommendation for neurological protection 1
4. Secure the aneurysm within 24 hours with surgical clipping or endovascular coiling to prevent rebleeding 3, 1, 6

Critical Pitfalls to Avoid

• Do not dismiss headaches without recognizing red flags such as progressive worsening over weeks, change in personality or cognition, and sudden onset of focal neurological deficit 1
• Do not delay aneurysm treatment beyond 72 hours unless medically necessary, as rebleeding risk is highest in the first 24 hours (3-4%) and increases progressively 1, 6
• Do not use prophylactic hypervolemia—maintain euvolemia and normal circulating blood volume, as hypervolemia does not prevent delayed cerebral ischemia 6
• Avoid systemic and metabolic insults including hyperglycemia, acidosis, electrolyte fluctuations, hypoxia, and hyperthermia—all worsen outcomes 6
• Do not automatically exclude high-grade patients (Hunt and Hess 4-5) from treatment, as 30% can achieve good clinical outcomes with aggressive treatment 6