Disease characteristics

Cerebrovascular manifestations of cerebral aneurysms most commonly include saccular or "berry" outpouchings on the circle of willis, the main circulatory system of the brain. Other configurations are also seen, but they are far less common. Most intracranial aneurysms (IA) are asymptomatic until they rupture, resulting in a subarachnoid hemorrhage (SAH). A SAH is a bleed that is generally around the brain, in the space between the skull and the brain. The onset of aneurysm formation and rate of progression is believed to be highly variable. The discrepancy between incidentally discovered IAs at autopsy and SAHs indicates that most IAs never rupture. IAs may be repaired prophylactically to prevent rupture.

 

Diagnosis/testing

The most commonly used tests to diagnose an IA are: cerebral angiography, Magnetic Resonance Angiogram (MRA) and Computed Tomography Angiogram (CTA). Conventional angiography enables visualization of the blood vessels and, therefore, anatomical characteristics of IAs and is suitable for surgical planning, but also carries risks of cerebral infarction (stroke) and hematoma (bruise) formation. MRA is a fairly reliable diagnostic test, detecting IAs as small as 2-3mm, and carries with it virtually no risk. It is generally not sufficient for surgical planning, however. The detection rate with CTA is similar to that with MRA. Adequate renal function must be established prior to CTA testing related to contrast elimination via the kidneys.

Computed Tomography scans (CTs) are the first diagnostic study used when SAH is suspected. CTs are very sensitive in detecting acute hemorrhage, however, sensitivity decreases over time from initial SAH. If there is strong suspicion of SAH and the CT is negative, a lumbar puncture (LP) should be performed. Xanthochromic CSF, caused by the break down of blood within the CSF, is diagnostic of SAH. Sequelae of SAH may include intracerebral hemorhage (ICH), intraventricular hemorrhage (IVH), brain edema, hydrocephalus, rebleed, vasospasm, infarction, brain shifts, herniation, brain death.

Environmental Risk Factors

Hypertension, smoking (half of SAHs are associated with it), Alcohol consumption (dose-dependent effect, that is, binge drinking, is also associated with worse outcomes following SAH related to increased incidence of rebleeding and vasospasms), cocaine (associated with earlier presentation, and decrease in average size of IA rupture. Studies show that IAs tend to rupture between five to ten millimeters in size. The majority of aneurysms are within the anterior circulation of the brain. IAs on the internal carotid artery (ICA) occur more frequently in females (36.8% to 18%) than in men; anterior circulation artery aneurysms occur more frequently in males (46.1% to 26.6%) than in females. Females are more likely to have multiple aneurysms. Onset of SAH is often associated with lifting or bending (12%), emotional strain (4%), defecation (4%), coitus (4%).

 

Related web sites and articles

 

• Intracranial Aneurysms: Current Evidence and Clinical Practice
• American Association of Neurological Surgeons
• Research Articles
• Gene Tests
• OMIM