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brain aneurysm

Cerebral Aneurysm · I67.1

A cerebral aneurysm is an abnormal structure in which the blood vessel wall expands like a balloon due to local weakening of the cerebral blood vessel wall. It is a dangerous vascular malformation that causes subarachnoid hemorrhage when ruptured, resulting in high mortality and serious neurological sequelae.

AT A GLANCE

At a glance

Brain aneurysms are found in approximately 2-5% of the adult population and are mostly asymptomatic. When it ruptures, subarachnoid hemorrhage, which manifests as ‘the worst headache of your life,’ occurs, and the 30-day mortality rate is approximately 25-50%. It commonly occurs around the Circle of Willis, especially in the branches of the anterior communicating artery (ACoA) and posterior communicating artery (PCoA). Noninvasive diagnosis is possible with MRA or CTA, and coil embolization and surgical clipping are the main treatments. Treatment decisions for unruptured aneurysms comprehensively consider size, location, and patient factors.

Definition and Overview

A cerebral aneurysm (intracranial aneurysm) is an abnormal structure in which the blood vessel wall swells locally due to structural weakness of the cerebral blood vessel wall. It is a relatively common vascular malformation found in approximately 2-5% of the total population, but when ruptured, it leads to subarachnoid hemorrhage (SAH), which is a dangerous condition with a high mortality rate.

By gender, the prevalence rate is approximately 1.5 times higher in women after the age of 40 than in men. Most cerebral aneurysms remain symptom-free throughout their lives and are discovered accidentally or partially rupture. The annual risk of rupture varies depending on size, but is generally estimated to be approximately 0.7-1.9%.

Occurrence site and classification

Approximately 85% of cerebral aneurysms occur in the bifurcation of blood vessels around the Circle of Willis. The most common sites are the anterior communicating artery (ACoA, approximately 30%), the internal carotid artery-posterior communicating artery bifurcation (ICA-PCoA junction, approximately 25%), and the middle cerebral artery bifurcation (MCA bifurcation, approximately 20%).

Depending on the form, they are classified into saccular (saccular, about 90% of all), fusiform, and dissecting aneurysms. The sac type is the most common and has a high risk of rupture. Depending on the size, they are classified into small (<7 mm), medium (7~12 mm), large (13~24 mm), and giant (≥25 mm). The larger the size, the higher the risk of rupture.

risk factors

Due to genetic factors, the risk of developing a brain aneurysm is significantly higher if two or more immediate family members have had cerebral aneurysm. Connective tissue diseases such as polycystic kidney disease, Ehlers-Danlos syndrome, and Marfan syndrome are associated risk factors.

Acquired risk factors include smoking (4-7 times increased risk), high blood pressure, and excessive drinking. In a longitudinal study of aneurysm growth, smoking was identified as the strongest predictor.

Rupture and subarachnoid hemorrhage

Rupture of a cerebral aneurysm is the most common cause, accounting for approximately 85% of subarachnoid hemorrhage (SAH). When it ruptures, blood instantly flows into the subarachnoid space, causing a rapid rise in intracranial pressure.

The 30-day mortality rate is approximately 25-50%, and approximately 50% of survivors remain with permanent neurological impairment. The risk of rebleeding within the first 24 to 48 hours after rupture is high at approximately 15 to 20%, necessitating rapid aneurysm occlusion.

Complications after rupture include rebleeding, vasospasm (4-14 days, cause of delayed cerebral ischemia), hydrocephalus (blockage of cerebrospinal fluid circulation), hyponatremia, and cardiac abnormalities (neurogenic cardiac dysfunction).

diagnosis

Magnetic resonance angiography (MRA) and CT angiography (CTA) are used as noninvasive screening tests for unruptured aneurysms. Both methods have high sensitivity for detecting aneurysms larger than 5 mm. Digital subtraction angiography (DSA) is the standard test for final diagnosis and treatment planning.

When subarachnoid hemorrhage is suspected, non-contrast CT is the first choice for immediate diagnosis. CT sensitivity within 6 hours of SAH onset is approximately 98%, but sensitivity decreases as time passes. If the CT is normal but SAH suspicion persists, cerebrospinal fluid xanthochromia is confirmed by lumbar puncture.

treatment

ruptured aneurysm

Endovascular coiling and surgical clipping are the two main treatments. In the ISAT randomized controlled trial, the rate of death or dependency at one year was lower with coiling than with clipping (23.7% vs. 30.6%). However, depending on the anatomical characteristics of the aneurysm, clipping may be more appropriate in some cases.

Oral administration of nimodipine is recommended to prevent vasospasm after rupture.

Unruptured aneurysm

Treatment decisions are individualized by comparing the risk of treatment complications against the risk of rupture. In the ISUIA study, small aneurysms less than 7 mm in diameter (especially in the anterior circulation) had a low risk of rupture of less than 0.1% per year, suggesting that follow-up is a reasonable option.

Larger than 7 mm, irregular shape, daughter sac, posterior circulation, symptomatic aneurysm, treatment is strongly considered when growth is confirmed.

QUESTIONS

Frequently asked questions

Q01What is a brain aneurysm?

A cerebral aneurysm is a condition in which part of the wall of a blood vessel in the brain becomes weak and swells like a balloon. In most cases, it is discovered incidentally and without symptoms. The problem is that when this bulge ruptures, blood flows into the space around the brain, creating a very dangerous condition. This is called subarachnoid hemorrhage. Brain aneurysms themselves are vascular malformations, so unless they rupture, there are often no serious symptoms.

Q02What are the symptoms of a ruptured cerebral aneurysm?

When it ruptures, you suddenly experience 'the worst headache you've ever experienced in your life' (thunderclap headache). Nausea, vomiting, neck stiffness (neck stiffness), light sensitivity, and decreased consciousness may occur. Some people may have a 'sentinel headache' days or weeks before the rupture. If you have any of these symptoms, you should go to the emergency room right away. The longer it is delayed, the worse the prognosis.

Q03How are brain aneurysms detected?

Most cases are discovered accidentally during an MRI for other reasons. Screening is recommended if there are two or more family members with cerebral aneurysm or subarachnoid hemorrhage. Magnetic resonance angiography (MRA) and CT angiography (CTA) are used as noninvasive screening tests, followed by digital subtraction angiography (DSA) for final confirmation. If you have high blood pressure, smoke, or a strong family history, discuss the need for screening with your specialist.

Q04Which is better for treating cerebral aneurysms: coiling or clipping?

Both methods are safe and effective treatments in appropriate patients. Coil embolization is a method of inserting a catheter into a blood vessel and filling the inside of an aneurysm with a coil. It is performed without a craniotomy. Surgical clipping involves opening the head and placing a clip around the neck of the aneurysm. In the ISAT study, coiling had a higher 1-year independent survival rate than surgery for ruptured aneurysms. A decision is made with the attending physician based on the location, size, and shape of the aneurysm, as well as the patient's age and general condition.

Q05Should all brain aneurysms discovered accidentally be treated?

Not all unruptured brain aneurysms can be treated immediately. If the size is less than 7 mm and the location is not at risk, follow-up is often chosen due to the low risk of rupture. The decision is made by comparing the risk of rupture with the risk of treatment complications. We comprehensively evaluate risk factors such as size, shape (irregular shape, daughter sac (bleb)), location, growth, patient age and general condition, high blood pressure, and smoking. Size changes are monitored through follow-up imaging at intervals of 1 to 2 years.

Q06Are there any limitations to my daily life if I have a brain aneurysm?

Once an unruptured cerebral aneurysm is discovered, some activities require caution. You may be advised to avoid activities that cause a sudden increase in blood pressure (lifting heavy objects, coughing strongly, or exercising vigorously). Quitting smoking, managing blood pressure, and drinking soberly are important. However, most daily activities are possible. Be sure to talk specifically with your doctor about what is acceptable and what to avoid.

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This article provides general medical information and does not replace an individual diagnosis or treatment plan. Please seek a medical assessment if symptoms persist.

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