A cerebral aneurysm is a focal weakening and outpouching of an artery in the brain, most commonly at the branch points of the circle of Willis. Population imaging studies estimate that 3-5% of adults harbor an unruptured cerebral aneurysm, with a worldwide prevalence of approximately 230 million people.
A cerebral aneurysm (intracranial aneurysm) is an abnormal focal dilatation of an intracranial artery resulting from weakening of the vessel wall. The most common type is the saccular ('berry') aneurysm, a focal outpouching at arterial bifurcations of the circle of Willis where the internal elastic lamina and tunica media are thinner. Other forms include fusiform aneurysms (diffuse expansion of an arterial segment, often atherosclerotic), mycotic aneurysms (infected, distal, multiple), traumatic pseudoaneurysms, and giant aneurysms (>25 mm). Approximately 85% of saccular aneurysms occur in the anterior circulation (anterior communicating artery, posterior communicating artery, middle cerebral artery bifurcation, internal carotid artery), and 15% in the posterior circulation (basilar tip, posterior inferior cerebellar artery, vertebral artery).
The key symptoms of Cerebral Aneurysm are: Sudden, severe headache — often described as the 'worst headache of life' or 'thunderclap' headache, peaking within seconds and reaching maximal intensity in under one minute, the hallmark of aneurysm rupture., Neck stiffness (meningismus) within minutes to hours of rupture, from blood irritating the meninges., Photophobia and phonophobia accompanying the sudden headache., Brief loss of consciousness or syncope in 10-20% of rupture cases, sometimes with seizure at onset., Nausea and vomiting often accompany the sudden headache., Focal neurological deficit (cranial nerve palsy, hemiparesis, language disturbance) — depends on aneurysm location and any blood collection or vasospasm., Painful third cranial nerve palsy with pupil dilation (oculomotor palsy from posterior communicating artery aneurysm expansion) — classic finding requiring urgent imaging even without rupture..
Diagnosis of cerebral aneurysm and aneurysmal subarachnoid hemorrhage hinges on rapid imaging in suspected rupture. In a patient with sudden severe headache, non-contrast CT of the head within 6 hours of symptom onset has >98% sensitivity for subarachnoid hemorrhage. Beyond 6 hours sensitivity drops, and lumbar puncture is performed if CT is negative and suspicion remains — xanthochromia on cerebrospinal fluid spectrophotometry confirms hemorrhage from 12 hours onward. Once subarachnoid hemorrhage is confirmed, CT angiography (CTA) or digital subtraction angiography (DSA) identifies the bleeding aneurysm in 85% of cases on first study; DSA remains the gold standard and is repeated within 1-2 weeks if initial study is negative. Clinical grading uses the Hunt and Hess scale (1-5) and World Federation of Neurosurgical Societies (WFNS) grade combining Glasgow Coma Scale with focal deficit; both predict outcomes. Modified Fisher scale (0-4) grades CT blood burden and predicts vasospasm risk. Unruptured aneurysms are usually found incidentally on imaging for unrelated symptoms (chronic headache, dizziness, head trauma, stroke workup, family or syndrome screening). MR angiography (MRA) is the screening modality of choice and is non-invasive; CTA provides higher resolution and is preferred for surgical planning. DSA is reserved for treatment planning or when MRA and CTA are equivocal. The PHASES (Population, Hypertension, Age, Size, Earlier subarachnoid hemorrhage, Site) score estimates 5-year rupture risk and supports shared decision-making for unruptured aneurysm management. Vascular and genetic screening is performed when family history, ADPKD, or connective tissue features are present.
Unruptured aneurysm prognosis is excellent for small (<7 mm) anterior-circulation lesions in older patients without high-risk features — 5-year rupture risk under 1% in many strata. Larger, posterior-circulation, symptomatic, or previously ruptured aneurysms have substantially higher rupture risk and warrant intervention. Treatment carries procedural risk: combined morbidity and mortality is approximately 3-5% for endovascular coiling, 5-10% for clipping, and 4-8% for flow diversion in expert centers. After aneurysmal subarachnoid hemorrhage, outcomes depend on initial clinical grade: Hunt and Hess grade 1-2 patients have 80-90% good outcomes; grade 4-5 have only 20-30% good outcomes. Overall 30-day mortality of aneurysmal SAH is 35-50%; among survivors approximately 30% are dependent or severely disabled at 6 months. Delayed cerebral ischemia from vasospasm affects 20-30% of patients and is a major driver of long-term disability. Cognitive impairment, fatigue, mood disorders, and reduced quality of life persist in roughly half of long-term survivors. Comprehensive stroke center care, multidisciplinary teams, and timely aneurysm securing have improved outcomes substantially over the last 20 years.
Cerebral aneurysm care requires multidisciplinary expertise from neurosurgery, interventional neuroradiology, neurology, and neurocritical care. Comprehensive stroke centers and dedicated cerebrovascular programs achieve substantially better outcomes than community hospitals, with mortality differences of 30-50% in major registries. Urgent transfer to a comprehensive center is indicated for any suspected ruptured aneurysm. Unruptured aneurysms benefit from formal multidisciplinary consultation to weigh PHASES risk, treatment risks, and patient values.
Find specialists →Aneurysm securing within 24-72 hours of rupture. Hospital stay typically 14-21 days for SAH care including vasospasm window (days 4-14). Rehabilitation in inpatient or outpatient settings over 3-12 months for moderate-to-severe deficit. Cognitive and mood symptoms may persist or emerge over 6-24 months and benefit from neuropsychological assessment and treatment. For elective unruptured aneurysm treatment: hospital stay 1-3 days for coiling and flow diversion, 4-7 days for clipping; return to most activities at 4-8 weeks; full clearance after follow-up imaging at 3-6 months.
Regular moderate aerobic activity (brisk walking, cycling, swimming) is encouraged for cardiovascular and blood pressure benefits. For patients with unsecured aneurysms, heavy isometric resistance training with Valsalva maneuvers (heavy weightlifting, max-effort straining) is generally discouraged because of transient hypertensive surges. After definitive treatment (coiling, clipping, flow diversion with confirmed occlusion), most activity restrictions are lifted on a case-by-case basis at 6-12 weeks. Discuss specific exercise plans with the treating neurovascular team.
Prefer Joint Commission-certified comprehensive stroke centers or Cerebrovascular Society of America/Society for NeuroInterventional Surgery-recognized programs. The treating neurosurgeon and interventional neuroradiologist should have documented high case volumes (typically >50 aneurysm cases per year for the program). Confirm 24/7 availability of both endovascular and microsurgical options for ruptured aneurysm management.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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