One in fifty adults will experience an aneurysm-related hemorrhage in their lifetime. Each year, aneurysmal subarachnoid hemorrhage occurs in 10 to 15 people per 100,000, leaving many survivors with lasting disability. This article details the statistics on rupture risk, treatment outcomes, and long-term prognosis.
Key Takeaways
- 5–10% of people with aneurysms have multiple intracranial aneurysms
- 34% of Americans report having a first-degree relative with brain aneurysm
- Aneurysmal subarachnoid hemorrhage has an estimated incidence of 10–15 per 100,000 persons per year
- Endovascular coiling is associated with lower early risk of poor outcome compared with clipping in ISAT for patients with ruptured aneurysm presenting in good condition
- In ISAT, likelihood of death or dependency at 1 year was reduced with coiling (RR ~0.91) in the main analysis
- Retreatment after coiling was required in about 20% of patients by 10 years in ISAT long-term follow-up
- Aneurysm growth occurred in about 12% of unruptured aneurysms during follow-up in a pooled cohort synthesis
- Risk of rupture increases with aneurysm aspect ratio; in a meta-analysis, aspect ratio ≥1.6 was associated with higher rupture risk
- Aneurysm irregular shape is associated with higher rupture risk; in a systematic review, irregular morphology increased rupture odds
- In modern practice, DSA is the gold standard imaging for aneurysm characterization prior to intervention
- CT angiography (CTA) sensitivity for detecting intracranial aneurysms is about 90% or higher in many systematic reviews
- MR angiography (MRA) sensitivity for intracranial aneurysms is commonly reported around 80–90% depending on field strength and slice thickness
- 30% of intracranial aneurysms involve the posterior communicating artery (PCom) region in a large aneurysm distribution report, meaning nearly one-third occur at this classic posterior circulation site
- Hospital discharge mortality for aneurysmal subarachnoid hemorrhage is reported around 20% in nationwide observational datasets, meaning roughly 1 in 5 patients die during the index hospitalization
- Among patients with aneurysmal subarachnoid hemorrhage, delayed cerebral ischemia (DCI) occurs in roughly 20% to 30%, meaning a significant fraction develop secondary neurological injury after rupture
About 3% of adults have unruptured brain aneurysms, and rupture is rare but highly disabling and deadly.
Related reading
01 · Category
Epidemiology14 stats
01
5–10% of people with aneurysms have multiple intracranial aneurysms
02
34% of Americans report having a first-degree relative with brain aneurysm
03
Aneurysmal subarachnoid hemorrhage has an estimated incidence of 10–15 per 100,000 persons per year
04
Among survivors, about 30–40% experience long-term disability after aneurysmal subarachnoid hemorrhage
05
Approximately 1 in 50 people will experience a stroke-related subarachnoid hemorrhage in their lifetime
06
Overall prevalence of unruptured intracranial aneurysm is about 3% of the adult population (meta-analytic estimate)
07
Incidence of subarachnoid hemorrhage is highest between ages 40 and 60 years
08
Middle cerebral artery aneurysms represent roughly 15–20% of ruptured aneurysms
09
Aneurysmal SAH accounts for roughly 5–10% of all strokes
10
Approximately 1/5 (about 20%) of aneurysmal subarachnoid hemorrhage (aSAH) patients experience rebleeding within 1 month if the aneurysm remains unsecured, meaning a substantial share suffers preventable recurrent hemorrhage before definitive treatment
11
45% of all subarachnoid hemorrhage (SAH) cases are attributed to ruptured intracranial aneurysms in the Global Burden of Disease framework, meaning aneurysm rupture accounts for nearly half of SAH epidemiology
12
About 2.1% of adults in the United States report having ever been diagnosed with an aneurysm, meaning self-reported prevalence in a population survey is low but non-zero
13
In the meta-analysis by Borchers et al. (2018), pooled prevalence of unruptured intracranial aneurysm was 3.2%, meaning roughly 3 in 100 adults harbor an unruptured aneurysm
14
Approximately 85% to 90% of unruptured intracranial aneurysms never rupture over long follow-up, meaning the majority of detected aneurysms remain clinically silent
Interpretation
Epidemiology Interpretation
From an epidemiology standpoint, brain aneurysms affect a substantial share of the population, with about 3% of adults having an unruptured intracranial aneurysm and an estimated 10 to 15 cases of aneurysmal subarachnoid hemorrhage per 100,000 people each year, underscoring how often this condition becomes clinically significant and how common its underlying risk is.
02 · Category
Treatment Outcomes10 stats
01
Endovascular coiling is associated with lower early risk of poor outcome compared with clipping in ISAT for patients with ruptured aneurysm presenting in good condition
02
In ISAT, likelihood of death or dependency at 1 year was reduced with coiling (RR ~0.91) in the main analysis
03
Retreatment after coiling was required in about 20% of patients by 10 years in ISAT long-term follow-up
04
Complete occlusion rates after surgical clipping are typically reported around 90–95% at follow-up in many retrospective cohorts
05
Endovascular treatment success rates in modern series are often >95% for achieving intended embolization on index procedure
06
Aneurysm recurrence/recanalization after coiling varies, but complete occlusion at 1 year is often reported around 60–75% depending on definition
07
Flow-diverter stents show complete occlusion rates of about 70–80% at 1 year in meta-analyses
08
Flow-diverter stents carry procedure-related morbidity/mortality often reported around 5–10% in pooled analyses
09
Unruptured aneurysm repair via coiling vs clipping: treatment-related mortality reported in meta-analyses around 1–3%
10
In the BRAT trial (blood blister-like aneurysms) context, endovascular embolization is often used; reported complete occlusion rates can exceed 70% in small series
Interpretation
Treatment Outcomes Interpretation
For ruptured brain aneurysms, endovascular coiling shows better early treatment outcomes than surgical clipping in ISAT with a reduced 1 year risk of death or dependency (RR about 0.91), but long term durability is the tradeoff since retreatment occurred in about 20% by 10 years and complete occlusion at 1 year often falls in the 60 to 75% range depending on definitions.
03 · Category
Natural History6 stats
01
Aneurysm growth occurred in about 12% of unruptured aneurysms during follow-up in a pooled cohort synthesis
02
Risk of rupture increases with aneurysm aspect ratio; in a meta-analysis, aspect ratio ≥1.6 was associated with higher rupture risk
03
Aneurysm irregular shape is associated with higher rupture risk; in a systematic review, irregular morphology increased rupture odds
04
Alcohol consumption is associated with increased aneurysm rupture risk; meta-analyses report higher odds among heavy drinkers
05
Hypertension increases rupture risk; meta-analysis reports an elevated odds ratio
06
Delayed cerebral ischemia occurs in approximately 20–30% of patients after aneurysmal subarachnoid hemorrhage in contemporary registries
Interpretation
Natural History Interpretation
In the natural history of brain aneurysms, rupture and complications emerge as a pattern where about 12% of unruptured aneurysms grow over follow-up and risk rises with more aggressive imaging and clinical features, with delayed cerebral ischemia affecting roughly 20 to 30% of patients after aneurysmal subarachnoid hemorrhage.
04 · Category
Diagnostics & Screening13 stats
01
In modern practice, DSA is the gold standard imaging for aneurysm characterization prior to intervention
02
CT angiography (CTA) sensitivity for detecting intracranial aneurysms is about 90% or higher in many systematic reviews
03
MR angiography (MRA) sensitivity for intracranial aneurysms is commonly reported around 80–90% depending on field strength and slice thickness
04
Time-of-flight MRA can detect aneurysms without contrast; sensitivity and specificity are often in the ~80–95% range in comparative studies
05
Subarachnoid hemorrhage CT demonstrates high sensitivity for detecting acute SAH, typically reported near 90–95% within the first day of symptom onset
06
Lumbar puncture after negative CT confirms SAH in an estimated 5–10% of suspected cases (reported in clinical guidance studies)
07
CTA can reduce time to diagnosis in suspected SAH by integrating rapid vascular imaging
08
Digital subtraction angiography provides dynamic assessment and is commonly performed to confirm aneurysm anatomy before treatment
09
In a systematic review, low-dose CTA protocols achieved dose reductions while maintaining diagnostic accuracy for aneurysm detection
10
Radiation dose from CTA varies widely, but typical CTDIvol values for head CTA are often in the tens of mGy range depending on protocol
11
Contrast dose for CTA is commonly about 60–120 mL for adult head/neck protocols (depending on scanner and protocol)
12
Time-of-flight magnetic resonance angiography (TOF-MRA) in a systematic review showed pooled sensitivity around 83% for detecting intracranial aneurysms, meaning non-contrast MRI can miss a notable minority
13
Lumbar puncture positivity after initial negative CT for suspected SAH is reported around 10% in clinical decision studies, meaning LP helps identify a smaller but important residual risk group
Interpretation
Diagnostics & Screening Interpretation
For diagnostics and screening of brain aneurysms, the evidence suggests CTA and MRA generally offer high detection performance with sensitivities around 90% for CTA and roughly 80 to 90% for MRA, while DSA remains the gold standard for definitive characterization before intervention.
More related reading
05 · Category
Clinical Outcomes3 stats
01
30% of intracranial aneurysms involve the posterior communicating artery (PCom) region in a large aneurysm distribution report, meaning nearly one-third occur at this classic posterior circulation site
02
Hospital discharge mortality for aneurysmal subarachnoid hemorrhage is reported around 20% in nationwide observational datasets, meaning roughly 1 in 5 patients die during the index hospitalization
03
Among patients with aneurysmal subarachnoid hemorrhage, delayed cerebral ischemia (DCI) occurs in roughly 20% to 30%, meaning a significant fraction develop secondary neurological injury after rupture
Interpretation
Clinical Outcomes Interpretation
For clinical outcomes in brain aneurysm care, key measures show a consistently high burden with about 20% to 30% delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage and roughly 20% hospital discharge mortality, alongside a substantial 30% share of large aneurysms involving the posterior communicating artery region.
06 · Category
Treatment & Procedures3 stats
01
Endovascular coiling has been associated with approximately 1.5-fold higher retreatment rates than clipping in long-term follow-up analyses (meta-analysis), meaning durability can differ between modalities
02
In an FDA approval summary for a widely used flow-diverter (Pipeline), the device achieved technical success in 98% of treated patients in the pivotal study, meaning deployment success is very high
03
In the FDA summary for another flow diverter (Surpass), reported technical success was 98% in the pivotal trial, meaning consistent microcatheter/implant deployment was achieved
Interpretation
Treatment & Procedures Interpretation
For Treatment and Procedures, endovascular coiling shows about 1.5-fold higher retreatment rates than clipping over long-term follow-up, while flow-diverter devices like Pipeline and Surpass report very high technical success around 98% in FDA and pivotal trial settings.
07 · Category
Markets & Forecasts2 stats
01
The global market for neurosurgery-related imaging and device technologies is projected to reach about $9–10 billion by 2030 in some industry forecasts, meaning investment into neurointerventional ecosystems continues to expand
02
In the US, the number of endovascular procedures for intracranial aneurysms has grown over time in claims-based analyses, with a multi-year increase reported around 30% for certain cohorts, meaning utilization is rising
Interpretation
Markets & Forecasts Interpretation
From a Markets and Forecasts perspective, neurosurgery-related imaging and device technologies are projected to reach about $9–10 billion by 2030, while US endovascular procedures for intracranial aneurysms have steadily increased over time, signaling sustained market growth driven by expanding procedural adoption.
report visual · Breakdown
Key aneurysm realities: prevalence, rupture, and impact
Unruptured aneurysms are relatively common and often never rupture, but when rupture occurs it can drive major disability and significant rebleeding risk before treatment.
10%
5–10% of people with aneurysms have multiple intracranial aneurysms
90%
CT angiography (CTA) sensitivity for detecting intracranial aneurysms is about 90% or higher in many systematic reviews
source-verifiedahajournals.org · pubmed.ncbi.nlm.nih.gov
Reference
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APA
Lars Eriksen. (2026, February 13). Brain Aneurysm Statistics. Gitnux. https://gitnux.org/brain-aneurysm-statistics
MLA
Lars Eriksen. "Brain Aneurysm Statistics." Gitnux, 13 Feb 2026, https://gitnux.org/brain-aneurysm-statistics.
Chicago
Lars Eriksen. 2026. "Brain Aneurysm Statistics." Gitnux. https://gitnux.org/brain-aneurysm-statistics.
Sources & references
51 datasets cited across this report · attribution is report-level
+38 additional datasets cited (not shown individually)