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Emergency and Acute Medicine – Cerebral Aneurysm
Core Overview
A cerebral aneurysm is a focal dilation or outpouching of a cerebral artery wall. It occurs in approximately 5–10% of the population. Rupture of saccular aneurysms accounts for 5–15% of all strokes. Distribution of ruptured aneurysms includes the anterior communicating artery (≈40%), internal carotid artery (≈30%), middle cerebral artery (≈20%), and vertebrobasilar system (≈5–10%).
Underlying Causes and Associations
Most cerebral aneurysms are saccular (berry) aneurysms, representing about 90% of cases. They develop at arterial bifurcations and weak points in vessel walls and increase in incidence with age. Multiple aneurysms occur in 20–30% of patients. Higher prevalence is seen with polycystic kidney disease, cerebral AVMs, connective tissue disorders (Ehlers–Danlos, Marfan), fibromuscular dysplasia, moyamoya syndrome, coarctation of the aorta, sickle cell disease, neurofibromatosis, and inflammatory or genetic disorders. Fusiform or dolichoectatic aneurysms account for about 7% and are more common in peripheral vessels. Mycotic aneurysms occur in roughly 10% of patients with bacterial endocarditis. Traumatic and neoplastic aneurysms are less common. A first-degree relative with an aneurysm nearly doubles lifetime risk. In children, aneurysms are rare but often large and located in the posterior circulation.
Clinical Presentation
Most aneurysms are asymptomatic until rupture. Sentinel headaches occur in 30–60% of patients and may precede rupture. Rupture leads to subarachnoid hemorrhage, typically presenting with a sudden, severe “thunderclap” headache described as the worst headache of life, often without focal deficits. Nuchal rigidity is common due to blood in the CSF. Seizures, syncope, or altered mental status may occur. Compression of adjacent structures can cause focal neurologic signs. ACA aneurysms may affect optic pathways, causing visual field deficits. Internal carotid–posterior communicating artery aneurysms often compress the oculomotor nerve, producing ptosis, diplopia, and a fixed dilated pupil. Cortical aneurysms may cause hemiparesis, aphasia, visual disturbances, or seizures.
Essential Evaluation
A complete neurologic examination is critical. Emergent noncontrast head CT detects 90–95% of subarachnoid hemorrhages. If CT is negative but suspicion remains high, lumbar puncture with CSF analysis is required.
Diagnostic Studies
Laboratory testing includes CBC, coagulation studies, electrolytes, renal and liver function tests, and arterial blood gas as indicated. Imaging includes chest radiography for pulmonary edema. Four-vessel cerebral angiography remains the diagnostic gold standard. CTA and MRA can identify aneurysms larger than 3 mm. Transcranial Doppler ultrasound is useful for monitoring vasospasm. Lumbar puncture is indicated when CT is normal but aneurysmal rupture is suspected.
Key Differentials
Consider arteriovenous malformation, intracranial hemorrhage (subdural, epidural, intracerebral), thromboembolic stroke, meningitis, encephalitis, migraine, optic neuritis, acute glaucoma, hypertensive encephalopathy, metabolic disturbances, sinusitis, and temporal arteritis.
Prehospital Priorities
Field neurologic assessment is valuable, including level of consciousness, speech, motor deficits, gait, and facial symmetry. Patients with suspected subarachnoid hemorrhage may require emergent airway protection and rapid transport to a facility with CT and ICU capabilities.
Initial Stabilization
Secure airway, breathing, and circulation. Provide supplemental oxygen and continuous cardiac and pulse oximetry monitoring. Rapid-sequence intubation may be necessary. Check blood glucose immediately in altered patients and correct hypoglycemia. Reverse anticoagulation when indicated. Control nausea and vomiting to prevent spikes in intracranial pressure. Treat seizures acutely with IV benzodiazepines and antiepileptics; routine seizure prophylaxis is not recommended.
Emergency Department Management
Early goals include prevention of rebleeding, vasospasm, and hydrocephalus. Management follows subarachnoid hemorrhage protocols. Early neurosurgical involvement is essential. Ventriculostomy may be required for intracranial pressure control and can reduce systemic hypertension.
Definitive Intervention
Timing of angiography and repair remains debated, though early intervention is favored to reduce rebleeding and vasospasm. Pediatric aneurysms carry a high hemorrhage risk and should be repaired early.
Pharmacologic Therapy
Blood pressure control is essential, commonly with labetalol or nicardipine. Nimodipine is used orally or via nasogastric tube to reduce vasospasm risk and should never be given intravenously. Antiemetics and stool softeners help prevent increases in intracranial pressure. Antiepileptics are used for active seizures.
Disposition and Follow-Up
All patients with aneurysmal subarachnoid hemorrhage require ICU admission. Symptomatic unruptured aneurysms warrant admission and urgent neurosurgical consultation due to high rupture risk. Incidentally discovered, asymptomatic aneurysms may be discharged with close neurosurgical follow-up. Annual rupture risk is approximately 1–2%, with treatment thresholds often considered in the 4–8 mm range.
Clinical Pearls and Pitfalls
A normal CT does not exclude subarachnoid hemorrhage—lumbar puncture is essential when suspicion persists. Vasospasm typically develops around day 3 after bleeding or surgery. Nimodipine reduces vasospasm-related morbidity but must never be administered intravenously. Avoid nitroprusside and nitroglycerin, as they can increase cerebral blood volume and intracranial pressure.
Core Overview
A cerebral aneurysm is a focal dilation or outpouching of a cerebral artery wall. It occurs in approximately 5–10% of the population. Rupture of saccular aneurysms accounts for 5–15% of all strokes. Distribution of ruptured aneurysms includes the anterior communicating artery (≈40%), internal carotid artery (≈30%), middle cerebral artery (≈20%), and vertebrobasilar system (≈5–10%).
Underlying Causes and Associations
Most cerebral aneurysms are saccular (berry) aneurysms, representing about 90% of cases. They develop at arterial bifurcations and weak points in vessel walls and increase in incidence with age. Multiple aneurysms occur in 20–30% of patients. Higher prevalence is seen with polycystic kidney disease, cerebral AVMs, connective tissue disorders (Ehlers–Danlos, Marfan), fibromuscular dysplasia, moyamoya syndrome, coarctation of the aorta, sickle cell disease, neurofibromatosis, and inflammatory or genetic disorders. Fusiform or dolichoectatic aneurysms account for about 7% and are more common in peripheral vessels. Mycotic aneurysms occur in roughly 10% of patients with bacterial endocarditis. Traumatic and neoplastic aneurysms are less common. A first-degree relative with an aneurysm nearly doubles lifetime risk. In children, aneurysms are rare but often large and located in the posterior circulation.
Clinical Presentation
Most aneurysms are asymptomatic until rupture. Sentinel headaches occur in 30–60% of patients and may precede rupture. Rupture leads to subarachnoid hemorrhage, typically presenting with a sudden, severe “thunderclap” headache described as the worst headache of life, often without focal deficits. Nuchal rigidity is common due to blood in the CSF. Seizures, syncope, or altered mental status may occur. Compression of adjacent structures can cause focal neurologic signs. ACA aneurysms may affect optic pathways, causing visual field deficits. Internal carotid–posterior communicating artery aneurysms often compress the oculomotor nerve, producing ptosis, diplopia, and a fixed dilated pupil. Cortical aneurysms may cause hemiparesis, aphasia, visual disturbances, or seizures.
Essential Evaluation
A complete neurologic examination is critical. Emergent noncontrast head CT detects 90–95% of subarachnoid hemorrhages. If CT is negative but suspicion remains high, lumbar puncture with CSF analysis is required.
Diagnostic Studies
Laboratory testing includes CBC, coagulation studies, electrolytes, renal and liver function tests, and arterial blood gas as indicated. Imaging includes chest radiography for pulmonary edema. Four-vessel cerebral angiography remains the diagnostic gold standard. CTA and MRA can identify aneurysms larger than 3 mm. Transcranial Doppler ultrasound is useful for monitoring vasospasm. Lumbar puncture is indicated when CT is normal but aneurysmal rupture is suspected.
Key Differentials
Consider arteriovenous malformation, intracranial hemorrhage (subdural, epidural, intracerebral), thromboembolic stroke, meningitis, encephalitis, migraine, optic neuritis, acute glaucoma, hypertensive encephalopathy, metabolic disturbances, sinusitis, and temporal arteritis.
Prehospital Priorities
Field neurologic assessment is valuable, including level of consciousness, speech, motor deficits, gait, and facial symmetry. Patients with suspected subarachnoid hemorrhage may require emergent airway protection and rapid transport to a facility with CT and ICU capabilities.
Initial Stabilization
Secure airway, breathing, and circulation. Provide supplemental oxygen and continuous cardiac and pulse oximetry monitoring. Rapid-sequence intubation may be necessary. Check blood glucose immediately in altered patients and correct hypoglycemia. Reverse anticoagulation when indicated. Control nausea and vomiting to prevent spikes in intracranial pressure. Treat seizures acutely with IV benzodiazepines and antiepileptics; routine seizure prophylaxis is not recommended.
Emergency Department Management
Early goals include prevention of rebleeding, vasospasm, and hydrocephalus. Management follows subarachnoid hemorrhage protocols. Early neurosurgical involvement is essential. Ventriculostomy may be required for intracranial pressure control and can reduce systemic hypertension.
Definitive Intervention
Timing of angiography and repair remains debated, though early intervention is favored to reduce rebleeding and vasospasm. Pediatric aneurysms carry a high hemorrhage risk and should be repaired early.
Pharmacologic Therapy
Blood pressure control is essential, commonly with labetalol or nicardipine. Nimodipine is used orally or via nasogastric tube to reduce vasospasm risk and should never be given intravenously. Antiemetics and stool softeners help prevent increases in intracranial pressure. Antiepileptics are used for active seizures.
Disposition and Follow-Up
All patients with aneurysmal subarachnoid hemorrhage require ICU admission. Symptomatic unruptured aneurysms warrant admission and urgent neurosurgical consultation due to high rupture risk. Incidentally discovered, asymptomatic aneurysms may be discharged with close neurosurgical follow-up. Annual rupture risk is approximately 1–2%, with treatment thresholds often considered in the 4–8 mm range.
Clinical Pearls and Pitfalls
A normal CT does not exclude subarachnoid hemorrhage—lumbar puncture is essential when suspicion persists. Vasospasm typically develops around day 3 after bleeding or surgery. Nimodipine reduces vasospasm-related morbidity but must never be administered intravenously. Avoid nitroprusside and nitroglycerin, as they can increase cerebral blood volume and intracranial pressure.
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