What is the management and treatment of brain aneurysms in individuals at risk or diagnosed with the condition?

Management and Treatment of Brain Aneurysms

Overview and Prevalence

Brain aneurysms (intracranial aneurysms) occur in approximately 1-3% of the adult population, with prevalence increasing from less than 1% in young adults to 4% in elderly patients. 1, 2

• Most unruptured aneurysms remain asymptomatic (51%), though some present with acute symptoms (17%) or chronic symptoms (32%) including headaches, visual deficits, cranial neuropathies, seizures, or ischemic events 1
• The catastrophic consequence of rupture is subarachnoid hemorrhage, which carries 37% mortality after hospitalization and results in severe disability in 17% of survivors 3

Diagnostic Approach

Digital subtraction angiography (DSA) remains the gold standard for definitive aneurysm characterization, though non-invasive imaging with CT angiography or MR angiography has 76-98% sensitivity and 85-100% specificity for detection. 1

• Initial screening typically uses CT angiography or MR angiography, which can detect most aneurysms except those smaller than 2-3 mm 1
• DSA with 3D rotational angiography provides superior resolution for treatment planning, particularly for visualizing perforators and defining neck anatomy, with less than 0.5% permanent neurological morbidity 1, 2

Size-Based Treatment Algorithm for Unruptured Aneurysms

Aneurysms <5mm

Conservative management is recommended in virtually all cases for asymptomatic incidental aneurysms smaller than 5mm. 1, 2

• The annual rupture risk is extremely low (0.05% per year for anterior circulation aneurysms <7mm without prior SAH history) 2
• Periodic follow-up imaging with MRA or CT angiography should be performed to detect growth 1, 2
• Any documented growth mandates immediate reconsideration for treatment 1, 2

Aneurysms 5-10mm

Aneurysms larger than 5mm in patients younger than 60 years should be seriously considered for treatment. 1, 2

• The yearly rupture risk for aneurysms 7-10mm is approximately 1%, making the cumulative lifetime risk substantial in younger patients 1, 4
• Treatment decisions must weigh this rupture risk against procedural morbidity, which includes 2.6% permanent neurological deficits and 0.9% mortality for endovascular treatment 4

Aneurysms ≥10mm

Large aneurysms 10mm or greater warrant strong consideration for treatment in nearly all patients younger than 70 years of age. 1, 2

• These carry substantially higher rupture risk and should be treated unless prohibitive comorbidities exist 1, 2

Age-Based Considerations

Patient age critically influences the treatment-versus-observation decision, as treatment risks increase with age while life expectancy decreases. 1, 2

• Patients younger than 60 years with aneurysms >5mm should have a lower threshold for treatment given their long life expectancy 1, 2
• Patients older than 65-70 years with small asymptomatic aneurysms may be managed conservatively, as treatment-related morbidity increases substantially with age 1, 2

High-Risk Features Mandating Treatment Consideration

With rare exceptions, all symptomatic unruptured aneurysms should be treated, as symptoms indicate mass effect or potential impending rupture. 1, 2

Absolute or Near-Absolute Indications:

• Symptomatic aneurysms causing cranial neuropathies (especially acute third nerve palsy suggesting expansion), headaches, visual deficits, seizures, or ischemic symptoms require urgent evaluation and treatment 1, 2
• Coexisting aneurysms in patients with prior SAH from a different aneurysm carry substantially higher rupture risk and warrant treatment 1, 2
• Documented aneurysm growth on serial imaging indicates instability and mandates reconsideration for treatment 1, 2

Strong Relative Indications:

• Posterior circulation location, particularly basilar apex aneurysms, which carry relatively high rupture risk 1, 2
• Positive family history of aneurysmal SAH or multiple family members with aneurysms 1, 2
• Daughter sac formation or other unique hemodynamic features suggesting instability 1

Treatment Modality Selection

Microsurgical clipping should be the first treatment choice in low-risk cases at experienced high-volume centers. 1, 2

• Surgical clipping provides more durable protection with rerupture rates of only 0.1-0.3% annually after complete occlusion 5
• Middle cerebral artery aneurysms demonstrate particular advantage with microsurgical clipping using current technology 5

Endovascular coiling may be preferred over surgical clipping for select aneurysms, particularly basilar apex and vertebrobasilar confluence aneurysms, in elderly patients, or when surgical morbidity is high. 2, 5

• Endovascular treatment demonstrates lower procedural morbidity (2.6% permanent deficits, 0.9% mortality) compared to surgery 4
• However, aneurysm recurrence occurs in 24.4% of coiled aneurysms, with retreatment required in 9.1% and annual rerupture rate of 0.9% 5, 4
• Aneurysms with favorable neck anatomy (neck diameter <5mm, neck-to-dome ratio <0.5) are ideal for endovascular coil embolization 4

Critical Implementation Requirements

Treatment must only be performed at high-volume tertiary centers (>35 cases/year) with experienced cerebrovascular teams, as results are significantly inferior at low-volume centers. 2, 5, 4

• Collaboration between microneurosurgeons and endovascular neurosurgeons is essential, using a decision-making paradigm designed to offer only low-risk treatments 1, 2
• Centers should have both surgical and endovascular capabilities, with multidisciplinary teams consulting >100 UIA patients per year 6
• Individual operators should perform the proposed treatment in >30 patients with aneurysms per year 6

Risk Factor Modification

Smoking cessation and hypertension control are essential modifiable risk factors that reduce aneurysm formation, growth, and rupture risk. 1, 2

• Smoking substantially increases prevalence and should be addressed through counseling in all patients with UIAs 1
• Blood pressure should be monitored and hypertension treated, as it plays a role in aneurysm growth and rupture 1
• Statins and acetylsalicylic acid are not recommended specifically for reducing rupture risk 6

Conservative Management Protocol

For aneurysms managed conservatively, periodic follow-up imaging is necessary to detect changes in size or configuration. 1, 2

• Imaging intervals should be individualized based on aneurysm size, location, and patient risk factors 1, 2
• Any documented growth, change in configuration, or development of symptoms mandates immediate reconsideration for treatment 1, 2

Management of Giant Aneurysms

Giant aneurysms (>25mm) may warrant nonoperative management when both treatment and natural history carry prohibitively high risks. 1, 2

• These complex lesions require careful individualized analysis of patient age, symptoms, and available expertise 1

Common Pitfalls to Avoid

Do not treat small (<5mm) asymptomatic aneurysms in elderly patients (>70 years) with significant comorbidities, as treatment risks outweigh rupture risk. 2

Do not assume all incidentally discovered aneurysms require treatment—the vast majority of small UIAs will never rupture (only 1 in 200-400 annually). 2

Do not rely solely on non-invasive imaging for treatment planning in complex cases—catheter angiography remains essential for definitive characterization. 2, 4

Never treat at low-volume centers (<20 cases annually)—transfer to high-volume centers with experienced teams is strongly indicated. 5

Do not assume complete occlusion eliminates all risk—long-term follow-up imaging remains necessary, particularly after endovascular coiling. 5, 4