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Ruptured Brain Aneurysms
When an aneurysm ruptures, it leads to bleeding within the head called hemorrhaging. This is a type of stroke. The term ‘stroke’ refers to the sudden onset of neurological symptoms due to a problem with the brain circulation. There are two ways a stroke can occur: ischemic or hemorrhagic. Ischemic stroke refers to the blockage of an artery, usually by a blood clot (see thrombus ), which may be due to the narrowing of arteries caused by arterial disease (see atherosclerosis). This interruption of the blood supply causes a lack of oxygen in the brain tissue the artery was feeding. This damaged brain tissue is referred to as an ‘infarct’.
Thrombus Formation - Click image for a larger view.
The type of stroke caused by a ruptured aneurysm is hemorrhagic, where a burst blood vessel or artery leads to bleeding. This bleeding causes compression and damage to the brain tissue. Aneurysm rupture almost always leads to bleeding within the subarachnoid space, between the skull and the brain. Hence, aneurysm ruptures are referred to as subarachnoid hemorrhages (SAH). Aneurysm ruptures are not the only cause of SAH; other causes include an arteriovenous malformation (AVM) or head trauma.
Subarachnoid hemorrhaging (SAH) can produce the following symptoms, depending on the amount of blood:
- A sudden severe headache that can last for days
- Nausea and vomiting
- Drowsiness and/or coma
Bleeding within the brain tissue itself is called intracerebral hemorrhage and is usually caused by the complications of hypertension with an aneurysm rupture (high blood pressure). It can produce the following symptoms:
- Weakness or paralysis of an arm or leg
- Difficulty with language and speech
- Vision impairment
- Seizures
Tissue damage resulting from arterial aneurysm rupture (on the surface
of the brain or within the brain)
A patient suffering the onset of subarachnoid hemorrhage should be rushed to a medical facility as quickly as possible, as early treatment greatly increases the probability of a better outcome.
Some prospective autopsy and angiographic studies suggest that the prevalence of unruptured intracranial aneurysms in the population may be as high as 3.6-6% (Vega et al., 2002), although most estimate that 1.5-5% of the general population has or will develop a cerebral aneurysm. ("What You Should Know About Cerebral Aneurysms", Cerebrovascular Imaging and Intervention Committee of the American Heart Association Cardiovascular Council, Randall T. Higashida, M.D., Chair, April 10, 2003)
The International Study of Unruptured Intracranial Aneurysms (New England Journal of Medicine, 339:1725-1733, 1998) found that for patients with no prior history of SAH, the rupture rate per year was 0.05% for patients with small aneurysms (less than 5mm diameter) and 0.5% per year for patients with large aneurysms (greater than 10mm diameter) or for patients with a past incident of SAH. The incidence of SAH in the population is 6 to 8 per 100,000 people overall, peaking in the sixth decade accounting for a quarter of cerebrovascular deaths (Wardlaw and White, The detection and management of unruptured intracranial aneurysms. Brain 123:205-221, 2000).
The chances that an unruptured aneurysm will bleed depend on the size, shape, location and symptoms that the aneurysm manifests:
- Smaller, uniformity — less chance of bleeding
- Larger, irregular shape — more likely to bleed
3-D CT scan reconstruction of small aneurysm
at bifurcation of arteriole (arrow designates aneurysm) - Click image for a larger view.
To view a video clip of the image, select one of the formats below.
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3-D CT reconstruction using Vitrea software
of giant aneurysm in the posterior Communicating artery - Click image for a larger view.
To view a video clip of the image, select one of the formats below.
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However, once an aneurysm has already bled, there is a very high re-bleeding rate. Treatment is recommended as soon as possible in this case.
In most cases, the catalyst for the bleeding of the aneurysm remains unknown. Studies have shown, however, that the following increase the risk of a rupture:
- Hypertension (high blood pressure)
- Strong Emotions such as anger can raise blood pressure and cause a rupture
- Blood ‘thinners’, including aspirin, Warfarin, and other medications or prescriptions drugs. Stimulants such as diet pills like ephedrine and amphetamines as well as recreational drugs like cocaine can cause aneurysms to rupture, as well.
Why is a Rupture Extremely Dangerous?
Although the incidence of an aneurysm rupture is relatively low, a subarachnoid hemorrhage is associated with a disastrously high fatality or substantial mental impairment rate as a result of its initial bleed or complications thereafter.
| Mild brain damage or full recovery - 15-30% |
| Vasospasm - 15-20% |
| Moderate to severe brain damage - 20-35% |
| Death - 30-40% |
More rupture statistics can be found in the Treatment and Treatment - Risks sections of this website.
There are several possible complications associated with a rupture. Here are a few key dangers.
- Hydrocephalus could result from fluid buildup as blood collects around
the base of the brain. This causes an enlargement of the spaces within
the brain that produce cerebrospinal fluid. This is treated often by
inserting a tube into the ventricles (fluid-filled space of the brain)
called a ventriculostomy tube, which drains into a bag at the patient’s
side.
- Vasospasm is also a possible complication associated with hemorrhaging
in the brain. The onset of vasospasm can be anytime between 3 to 14
days after the initial hemorrhage. The blood released into the fluid-filled
spaces at the base of the brain can chemically irritate the other vessels
located there, causing them to constrict in response. This constricting
could lead to a stroke or blockage of a vessel by plaque or some other
debris causing it to rupture in a second hemorrhagic event. This constriction
of normal blood vessels is also likely to interrupt blood flow to healthy
brain tissue, leading to even more brain damage.
The treatment of vasospasm involves a host of different medicines, including those that increase blood pressure. This treatment option of elevating blood pressure is usually administered only after the ruptured aneurysm has been treated first.
Another option is to directly manipulate the vessels, using a catheter to open the vessel wall with a stent (a complete explanation of stenting and balloon-assisted stenting can be found in the glossary), medication, or both. Vasospasm and the threat of spastic vessels fade over several days. The sooner a ruptured aneurysm is treated, the lesser the chance of vasospasm setting in.
- Difficulty breathing which is often treated with a mechanical ventilator
- Infection
Once blood enters the brain and the surrounding space, there is also direct damage to the brain tissue and functions. The amount of damage is proportional to the amount of blood leaked. This damage is caused by the swelling, compression and irritation of the brain tissue by the blood.
Getting treatment immediately is optimal to avoid additional complications. Other complications and delayed effects of a hemorrhage include fever, headaches, seizures, and strokes, all of which can be treated with various medicines, or procedures. For more information, see Recovery.
The statistics on recovery of complete neurological functions vary depending
on the treatment pursued. In 50% of hemorrhage cases, the bleeding results
in death. Although a hemorrhage is a very serious occurrence, the techniques
for handling them have greatly improved and the proportion of patients
who survive is increasing.
Although treatment of the aneurysm will not reverse the damage already
inflicted on the brain from a bleed, stopping the bleeding will prevent
further damage. Once the patient has been treated, the recovery of any
affected brain functions can occur with rehabilitation therapy.
Diagram of the lobes of the brain, with their
associated functions. The damage a hemorrhage may inflict on mental integrity
varies based on location.
There are many studies presenting different statistics as to the recovery rates based on whether or not the patient was treated and what type of treatment was used. This site will present several of the more standard studies.
If the patient is not near a hospital, and the rupture is left untreated, there is about a 40% chance of the bleeding slowing and eventually stopping altogether. The aneurysm would heal by blood clotting action, and the patient would survive. However, in 30% of cases left untreated where the patient survives, the bleeding results in some amount of brain damage ranging from morbidity (severe incapacitation, usually paralysis or coma) to mild neurological deficits, such as speech defects.
Here is more information on Brain Treatment and Risks.
