Brain aneurysms (also called cerebral aneurysms) usually develop in adulthood at a higher rate, which increases with age. About 2% of Americans have a brain aneurysm. Some patients may have more than one.
The most common type of brain aneurysm is called a berry aneurysm. It is a saccular (balloon-like) outpouching on the wall of a cerebral artery. Most berry aneurysms are less than 1/2 inch in size. They typically develop at the point where certain blood vessels branch from their major brain artery.
Berry (saccular) aneurysms are generally found on blood vessels which course over the brain’s surface in the space containing cerebrospinal fluid (called the subarachnoid space). Most unruptured berry aneurysms do not produce any symptoms (and go undetected) unless they bleed. However, with modern brain imaging, more unruptured aneurysms are being discovered by accident.
The main risk of a brain aneurysm is that it may rupture or burst. If this happens, blood spills into the subarachnoid space. This event is commonly referred to as an aneurysmal subarachnoid hemorrhage (SAH). Sometimes, it may also produce a blood clot within brain tissue itself. This is called an intracerebral hemorrhage (ICH). A person suffering an aneurysmal SAH can be very ill and face a risk to life. There is also a substantial risk that the aneurysm can rupture again.
Other types of aneurysms are much less common. These include fusiform (bulging of an entire section of blood vessel), mycotic (infectious) and traumatic aneurysms.
Signs and Symptoms
Unruptured cerebral aneurysm Most do not produce any signs or symptoms (asymptomatic) and are detected by accident on a brain imaging study. Occasionally an unruptured aneurysm becomes symptomatic by pressing on a structure. This will usually produce symptoms involving the eye (local pain, a drooping eyelid, pupil changes or a disturbance with eye movement) on the affected side. Very rarely, an unruptured aneurysm may grow to giant size (1 inch or more) and cause seizures or tumor-like symptoms.
Ruptured cerebral aneurysm The key symptom is an explosive, instantaneous headache, sometimes called a “thunderclap” headache. Although this sudden headache may not be incapacitating, most patients say it is the worst headache they ever experienced. With SAH, there may also be loss of consciousness or a seizure. Neck stiffness, nausea and vomiting and impaired thinking or memory are also commonly seen. The blood pressure is usually elevated. Some may lapse into an immediate coma.
The exact cause of a berry (saccular) aneurysm is not fully understood. They are more common in women. Missing enzymes, inflammation, atherosclerosis and mechanical stresses on the blood vessel wall may contribute to its formation.
Generally, brain aneurysm are not felt to be hereditary. They are rarely found in children. However, testing to screen for a brain aneurysm is reasonable to consider as an adult if you have two or more first-degree relatives who are known to have had a brain aneurysm.
If you have a brain aneurysm, there are things you can do which may decrease its potential risk for rupture. The most important is to stop smoking. Cigarette smoking triples the risk for rupture. Cocaine use, heavy alcohol consumption (especially binge drinking) and elevated blood pressure are also risk factors you can modify.
Most unruptured aneurysms are discovered accidentally on a brain imaging test such as a CT or MRI scan . In patients who are suspected of having a subarachnoid or possibly an intracerebral hemorrhage, the initial emergency evaluation typically begins with a CT scan of the brain. The following tests are then used: computed tomographic angiography ( CTA ), magnetic resonance angiography ( MRA ), cerebral angiography and/or lumbar puncture/ spinal tap.
If you have been diagnosed with a brain aneurysm, the physicians at Goodman Campbell look at many key factors about the aneurysm to determine their best recommendation for treatment. They will also consider your age, general health, family history, anxiety over the aneurysm and the risks associated with treatment.
- Observation This consideration normally applies only to an unruptured, asymptomatic aneurysm. Most will not bleed. The overall risk that an unruptured aneurysm may bleed is about 5 in 1000 per year. Depending on specific characteristics of the aneurysm, the actual risk may range from as low as 1 in 2000 per year up to 1 in 100 per year. If you and your physicians feel that observation represents the best option, imaging of the aneurysm (usually with MRA or CTA to check for any change) will often be arranged on a routine basis.
- Aneurysm clipping/reconstruction This surgical procedure places a clip across the neck (or base) of an aneurysm to seal it off and reconstruct the normal blood vessel wall. Considerations for surgery include younger age, aneurysm architecture and location, SAH with multiple suspect aneurysms and presence of a large ICH.
- Aneurysm coiling/stenting / flow diversion These neuro-interventional procedures are done through a catheter (a long, small tube) which is guided through an artery to the aneurysm. The primary considerations for endovascular treatment are the architecture and location of the aneurysm. Coils can be used as primary treatment in SAH. Because stents and flow diverters require blood-thinning medications, their use may be delayed in SAH. Aneurysms treated by interventional techniques are often monitored for many years by MRA.
- Ventriculostomy Hydrocephalus can be seen in about a quarter of patients who have SAH. If it is causing symptoms, an external ventricular drain is placed to divert the cerebrospinal fluid to the outside through a closed system.
- Cerebral angioplasty This neuro-interventional procedure is used to treat symptomatic vasospasm following SAH. The narrowed artery may be opened with a mechanical device or injected medications.
The length of hospital stay for aneurysm treatment depends on whether the aneurysm is unruptured or ruptured. Surgical or endovascular treatment of an unruptured aneurysm typically involves an overnight to several day hospitalization. Treatment is done to prevent bleeding. Once an aneurysm ruptures, everything is more complex. Hospitalization will usually involve a stay of 10–30 days, often with the need for additional rehabilitation therapies (physical, speech and/or occupational). The need for additional therapy is the result of problems created by the SAH itself.