Pathophysiology of Brain Aneurysm and Vascular Disease
The Vascular System of the Body
Blood distributes oxygen, food substrates and other important components to the different parts of the body, while also helping to eliminate wastes. As blood travels through the elastic blood vessels, composed of arteries, vein and capillaries, it is pumped by the heart, which is considered to be a modified part of the vascular or circulatory system.
The heart is a muscular organ that pumps the blood to the other parts of the body through the arteries, which distribute or feeds oxygen and food to the cells. These substrates are metabolized, and waste products are returned to the circulation through the veins for elimination. Capillaries connect arteries and veins.
Atherosclerosis, a Disease of the Vascular System
Vascular disease is any condition that affects any part of the circulatory system, including the blood. This includes a wide range of disease entities, but for purposes of more specific discussion, peripheral artery disease will be described in particular.
Coronary arteries (which supply the heart) and peripheral arteries (which supply other parts of the body) are elastic vessels that feed organs, which are sensitive to changes in their diameters. A decrease in diameter of an artery may be a result of spasm in the muscle cells of the arterial wall, or a consequence of fatty deposits (plaque) on these walls. As a person ages, cholesterol and fat are deposited on the arterial walls, causing these to harden, decreasing their diameters and diminishing their original elasticity. This condition is called atherosclerosis.
As the disease progresses, the blood supply to the receiving organ is severely diminished and it suffers from ischemia, or lack of oxygen, which is damaging to the organ. Consequently, organ function is affected and may lead to organ failure.
Another possible consequence of atherosclerosis is the weakening of the walls of the artery, causing it to bulge like a balloon when pressure increases. This bulge or weakening on the arterial wall is called an aneurysm, and it can develop in different parts of the body. The most common sites for aneurysms are the brain and the aorta (the biggest artery in the body).
Risk factors for the development of atherosclerosis and aneurysms are advanced age, diabetes, hypertension, obesity, alcohol consumption, tobacco smoking and hypercholesterolemia.
Although atherosclerosis is the most common cause of aneurysms, other causes include congenital conditions, infections and syphilis.
The brain has a network of small arteries that can form aneurysms. The most common location for the formation of these is in the circle of Willis which is at the base of the brain.
An aneurysm in the brain is usually small and asymptomatic; however, when it increases in size it may impinge or apply pressure on other structures and cause symptoms like headache, neck pain, blurring of vision and speech changes, depending on its location and size. In the presence of stress and high blood pressure an enlarged aneurysm may rupture and result in uncontrolled bleeding in the brain. This is called a brain stroke or subarachnoid hemorrhage, and it may lead to death, if untreated.
Symptoms of stroke or sudden rupture of brain aneurysm are a sudden severe headache, nausea and vomiting, and fainting or seizures.
Vascular disease and brain aneurysm usually progress slowly and are often asymptomatic. Vascular disease that leads to a decrease in blood supply of an organ leads to signs and symptoms like chest pain, fainting, seizures, leg pain, kidney failure and high blood pressure. When these symptoms are manifest, people usually seek consultation and, after physical examination, a series of laboratory tests will be performed, including:
Blood tests to screen for diabetes, lipid profile, liver and kidney function tests, etc.
Electrocardiogram, to detect changes in the heart
Blood pressure monitoring
Radiologic exams to find any structural changes in the heart, other organs and vessels
Aneurysms are usually detected by radiologic exams, like CT scan, angiogram and magnetic resonance angiography.
Treatment and Prevention
Vascular disease can be treated medically to prevent progression to organ failure. Drugs may include statins, to decrease the lipids in the arteries, and antihypertensives, to prevent ischemia. Depending on the affected organs, treatment also includes heart medications and drugs to control blood sugar levels, maintain kidney function and optimize brain circulation. Diet supplements, antioxidants and other medications to treat symptoms may also be given.
Small and asymptomatic brain aneurysms that are detected incidentally may be initially observed for growth. As they grow larger and become symptomatic, there are treatment options, depending on the size of the aneurysm and the general condition of the patient. Conservatively, tiny metal coils may be inserted into the artery with the aneurysm, to prevent rupture. Otherwise, open surgery of the brain to clip the base of the artery will be performed, to stop it from bleeding.
Vascular disease and brain aneurysm that are due to atherosclerosis are preventable, since they are caused by lipid deposits from a diet rich in fat and cholesterol. Choosing foods with less fat content and more fiber, coupled with regular exercise, can prevent obesity, diabetes, hypertension, heart disease and other conditions related to vascular disease.
WebMD. “The Heart and Vascular Disease,” https://www.webmd.com/heart-disease/vascular-disease.
WebMD. “Brain Aneurysm - Topic Overview,” https://www.webmd.com/brain/tc/brain-aneurysm-topic-overview?page=1.