"Brain aneurysm" is a scary term, but how much do you really know about this condition?

What causes brain aneurysms?
Brain (or cerebral) aneurysms develop as a bulge in the wall of an artery in the brain. These bulges often resemble a balloon or berry forming from the blood vessel. They can be caused by a number of conditions. Smoking and high blood pressure are thought to increase the risk of brain aneurysm. Genetics also play a role, says Rishi Gupta, MD, Associate Professor of Neurology, Neurosurgery and Radiology at the Emory University School of Medicine.

Less common causes of brain aneurysms include fibromuscular dysplasia and connective tissue disorders such as Ehlers-Danlos syndrome (type IV) and Marfan syndrome. However, the majority of brain aneurysms have no known cause.

Who is at risk?
While many brain aneurysms occur in people with no risk factors, there are some people experts believe to be more prone to develop aneurysms. Here are the most important risk factors:

• Family history: Those with first-degree relatives, such as siblings or parents, who have had a brain aneurysm are at increased risk.
• Smoking: Smoking not only increases the risk of brain aneurysms, but increases the risk of rupture as well.
• Connective tissue disorders: People with conditions such as Marfan syndrome are at increased risk as are people with the other conditions listed above.
• Hypertension: A history of chronic high blood pressure may increase the risk of brain aneurysm.

What are the symptoms of a brain aneurysm?
While many people may think of brain aneurysms as sudden events requiring emergency treatment, they usually have no symptoms at all. It's the rupturing of an aneurysm that can lead to severe symptoms, and even death. "In some rare cases, an aneurysm can cause a cause a cranial nerve palsy; but typically, aneurysms are asymptomatic unless they rupture," says Dr. Gupta. "When they do rupture, patients present with the worst headache of their life. And, unfortunately, when that it occurs it often carries a high mortality rate."

How likely is an aneurysm to rupture?
Approximately 2 percent of the population has brain aneurysms. Of that number, about 50,000 people a year suffer from subarachnoid hemorrhage (when blood leaks into the space around the brain) due to a ruptured aneurysm. "Some features, such as size of the aneurysm, may be predictive of rupture," says Dr. Gupta. "It is generally felt that larger aneurysms have a higher probability of rupture."

How are brain aneurysms diagnosed?
Diagnosis of an aneurysm depends on what leads a person to seek medical attention. Since many brain aneurysms go unnoticed until they rupture, many people with aneurysms first present to a physician or medical clinic with a subarachnoid hemorrhage. In such instances, they will undergo a catheter angiogram, says Dr. Gupta. "This involves femoral artery puncture and catheter manipulation under X-ray to identify the location of the aneurysm," he explains. "CT angiography can also be used to identify cerebral aneurysms.

"Unruptured aneurysms are typically detected incidentally when patients undergo MRA imaging of the brain for other symptoms, such as stroke, migraine headaches or dizziness," continues Dr. Gupta.

What are the current treatments?
Once again, the course of action depends on the type of aneurysm. "For ruptured aneurysms, treatment with coil embolization (a minimally invasive approach performed from the groin in which metallic coils are placed in the aneurysm sac to treat the aneurysm) has been shown to have a 6.9 percent absolute risk reduction in mortality and disability from an aneurysm compared to surgical clipping," says Dr. Gupta. "In ruptured aneurysms, which are challenging to treat with coil embolization, microsurgical clipping with an open craniotomy can also be performed to secure the aneurysm.

For a ruptured aneurysm, the evidence points to early treatment as necessary for preventing re-rupture. Ideally, this should be performed within 12 to 24 hours from diagnosis of the bleed. "For non-ruptured aneurysms, the treatment decision for coiling versus clipping is determined based on the age of the patient, the number of aneurysms and the locations," he continues.

People who have had a ruptured brain aneurysm in the past also require frequent surveillance for the development of new aneurysms. "People with a strong family history or presence of a collagen vascular disorder may also be screened," says Dr. Gupta.

"If someone presents with an acute third nerve palsy (abnormal movement of the eye or abnormalities of the eyelid or pupil), they are screened as well."

Do all aneurysms require treatment? Smaller aneurysms are at lower risk for rupturing. So if one is detected, sometimes a watch-and-wait approach is applied. "Typically aneurysms less than 5 mmÑparticularly in an older personÑmay be followed with sequential imaging to see if the aneurysm enlarges," says Dr. Gupta. "Younger patients have a higher cumulative risk of rupture because they have more years to live, but the risk of treatment must be balanced against the natural history. Generally, younger patients with aneurysms greater than 5 mm are considered for surgical or endovascular treatment as their cumulative risk is felt to be high for rupture. In patients older than 60 years old, careful consideration for treatment is based on the presence of other risk factors."

What's the outlook for people who've had an aneurysm?
Unfortunately, the prognosis for ruptured aneurysms is not good. In fact, roughly 40 percent of people who have one don't even make it to the hospital in time for treatment. And those who do survive have an uphill battle ahead. "Survivors have tremendous disability with cognitive skills, depression and often impairment of motor or speech function," explains Dr. Gupta.

Patients with non-ruptured aneurysms who are treated can do well with coiling or clipping. The complication rate is less than 5 percent. However, many experts still feel this risk is too highÑespecially since there is no definitive evidence that treatment of non-ruptured aneurysms reduces the risk of ruptures in the long run. According to Dr. Gupta, continued research in the field of brain aneurysms will help lead to a better understanding of the condition, as well as improved treatments.