Understanding Brain Aneurysm: Symptoms, Causes & FAQs

How Does a Brain Aneurysm Happen?

A brain aneurysm is a bulge or ballooning in a blood vessel wall caused by a weak or thin spot in that wall. Small aneurysms tend not to cause any problems. However, larger aneurysms can press on nerves and the surrounding tissue or can rupture, causing serious health problems. Blood flowing through arteries is under high pressure; arteries have thick walls to cope with this. The thinning of the vessel walls and loss of elastic fibers causes a weakness in the walls, resulting in the wall bulging in response to pressure and an aneurysm forming. A rupture occurs when the blood vessel in the brain bursts, releasing blood into the space surrounding the brain. This is called a subarachnoid hemorrhage. A ruptured aneurysm is life-threatening, with the possibility of causing a stroke, permanent nerve damage, or dangerous swelling and pressure on the brain.

Types of Brain Aneurysm

There are five main types of brain aneurysms:

  • Saccular aneurysm – appears as a rounded berry-like sac filled with blood attached to a main artery or an artery branch; it is the most common type of aneurysm.
  • Fusiform aneurysm – the blood vessel balloons or expands in all directions.
  • Mycotic aneurysm – caused by an infection weakening the artery wall.
  • Dissecting aneurysm – expansion of only the outer layers of the artery wall; also known as a pseudo-aneurysm and most commonly occurs from a traumatic injury.
  • Blister aneurysm – has a blister-like appearance; most commonly found on the carotid artery and are at an increased risk of bleeding.

Brain aneurysms can occur anywhere in the brain, but are most commonly found in the major arteries at the base of the skull.

How Common Are Brain Aneurysms?

Unruptured brain aneurysms are relatively common; they are found in approximately 3-5 percent of the general population. Approximately 6.8 million people in the US currently have an unruptured brain aneurysm. Ruptured aneurysms have a lower prevalence but drastically worse effects. The annual rate of rupture is estimated at 8-10 in 100,000 people – so approximately 30,000 people per year in the US suffer a rupture. Rupture depends on the size of the aneurysm and the location of the aneurysm.

The prevalence of aneurysms differs depending on population demographics. Brain aneurysms are approximately 60 percent more common in women than men, increasing to twice as likely after menopause. Age also affects aneurysm prevalence, with the highest prevalence in people between 35-60 years old. Aneurysm prevalence can also depend on ethnicity, with African Americans and Hispanics showing a higher prevalence than Caucasians.

What Are the Symptoms/Warning Signs to Look Out For?

Early Symptoms of Unruptured Brain Aneurysms

Unruptured brain aneurysms are commonly asymptomatic; however, sentinel hemorrhages (a small amount of blood leaking from the brain aneurysm) or the expansion of the aneurysm to press on nerves or tissues can cause symptoms. These symptoms will act as warning signs of a brain aneurysm and could be a sign of a brain aneurysm rupture before it happens.

Brain aneurysm symptoms before rupture can include:

  • Vision problems, including peripheral vision deficits, double vision, diminished eye movements, and eye pain.
  • Thinking, processing, or perceptual problems, including decreased concentration.
  • Loss of balance and coordination.
  • Speech difficulty.
  • Numbness or weakness.
  • Paralysis on one side of the face.
  • A dilated pupil in the eye.

Symptoms of Ruptured Aneurysms

Ruptured brain aneurysm symptoms, on the other hand, will be more extreme. These can include:

  • A thunderclap headache – a sudden, extremely severe headache, often described as “the worst headache of my life”; this symptom is always present when an aneurysm ruptures.
  • Neck pain.
  • Nausea and vomiting.
  • Light sensitivity.
  • Loss of consciousness (brief or prolonged).
  • Dilated pupils.
  • Seizures.

Medical attention should be sought immediately if a rapid-onset, severe headache is experienced, especially in combination with any of the above-listed symptoms.

Causes of Aneurysms

Genetic Factors

Although the genetics of brain aneurysms are not fully understood, certain associations have been found. The risk of developing a brain aneurysm is greater in an individual with 1 first-degree relative who has experienced an aneurysm, rising to 8 percent with 2 first-degree relatives with the condition. Certain heritable diseases can also increase the risk of aneurysms, including polycystic kidney disease, Ehlers-Danlos type IV, fibromuscular dysplasia, and other diseases affecting connective tissue.

Lifestyle Factors

Several lifestyle factors can increase the risk of developing aneurysms. Smoking is a well-established risk factor for both aneurysm formation and rupture. Cigarette smoke and nicotine increase the blood vessel wall's sheer stress, thus increasing the likelihood of an aneurysm forming. The risk of aneurysm rupture is significantly increased by smoking; increasing further with a longer duration and increased intensity of smoking. Smokers are 3-6 times more at risk for aneurysm rupture than non-smokers, and this can be as high as 10 times for heavy smokers and female smokers.

Smoking also increases the likelihood of developing multiple aneurysms. High blood pressure significantly increases the risk of developing a brain aneurysm and the risk of rupture. When blood pressure is increased, the vessel walls experience increased sheer stress. Over time, this will weaken the vessel walls, leading to the formation of aneurysms and rupture. High blood pressure also causes vascular inflammation, which in turn disrupts the vessel walls and increases the risk of aneurysm formation. Illegal drug use can similarly influence the chances of developing an aneurysm. Cocaine causes blood vessel inflammation and high blood pressure, both of which contribute to aneurysm formation.

How Are Brain Aneurysms Diagnosed/Detected?

There are several diagnostic methods and technologies that doctors use to check for brain aneurysms, the most common of which are brain imaging scans. Computed tomography (CT) scans use X-rays to create an image of the brain. Before scanning, a contrast dye can be injected into the bloodstream. The CT angiography scan will produce images of blood flow through the blood vessels in the brain and can, therefore, detect aneurysms.

Magnetic resonance imaging (MRI) scans can also be used to detect aneurysms. MRIs produce a highly detailed image of the brain – without using any ionizing radiation (such as X-rays). MR angiograms can be used to produce detailed images of the brain blood vessels, identifying the presence and location of aneurysms. Cerebral angiograms are a further method of aneurysm detection. These involve the insertion of a catheter, which is guided to the blood vessels surrounding the brain, where a contrast dye is injected. X-ray images are then produced to image the blood vessels.

Can Early Detection Prevent Aneurysms?

It is not possible to prevent brain aneurysms from forming. However, early detection of aneurysms can reduce the risk of rupture and, therefore, reduce the risk of serious complications. Brain aneurysms can kill you – the mortality rate for ruptured aneurysms can be as high as 50 percent, and even for those who survive, approximately 66 percent suffer permanent brain damage. However, if detected early, treatments can be carried out to ‘clip’ an aneurysm, preventing blood from entering the aneurysm and therefore decreasing the risk of rupture. Regular MRI or CT scans can identify aneurysms before rupture occurs, allowing early treatment and thus drastically reducing the risk of serious complications. Routine screenings are particularly advised for those with a family history of aneurysms but are also recommended for those interested in preventive healthcare.

Summary: Understanding Brain Aneurysm: Symptoms, Causes & FAQs

Brain aneurysms can result in serious health complications or even death if left undiagnosed and untreated. Ruptured aneurysms produce classic symptoms, including a thunderclap headache. Unruptured aneurysms are often asymptomatic, but early detection using imaging techniques such as MRI or CT scans allows detection before rupture occurs. Although it is not possible to prevent brain aneurysms, lifestyle changes (such as quitting smoking and lowering blood pressure) can reduce the risk of developing brain aneurysms and reduce the risk of their rupture. Regular screenings are recommended as they can detect aneurysms before they rupture and allow treatment of the aneurysm.