While it is true that strokes are more common in the elderly, they can occur in young adults, and even in adolescents and children. "Young stroke" in medical research generally refers to patients under the age of 50.
In many patients, particularly in the 40-50 year old range, strokes are due to premature atherosclerosis, the same disease which causes heart attack and "hardening of the arteries."
These patients typically have risk factors for atherosclerosis, such as hypertension, diabetes, smoking and elevated cholesterol. Often there is a family history of stroke or heart disease at a young age.
African-Americans are several times more likely to have a stroke at a young age than whites, even if risk factors are taken into account. The reason for this difference is not known.
Strokes can also occur in young patients without risk factors for atherosclerosis, but the causes are diverse and can be difficult to diagnose given the uncommon nature of these diseases.
In the evaluation of a young stroke patient, physicians evaluate three basic areas to determine the cause: the heart, the blood vessels supplying the brain, and the blood clotting system.
Congenital heart disease is a leading cause of stroke in children. People with artificial heart valves must often be kept on anticoagulants ("blood thinners") to prevent clots from forming on the valves.
Other heart conditions, such as mitral valve prolapse, may produce clots, but these are infrequent and can usually be managed with medicines such as aspirin effectively.
Infection of a heart valve, referred to as endocarditis, is a serious medical condition that can cause bits of infected clot to travel to the brain, causing both stroke and aneurysms.
Endocarditis can occur in patients with damaged heart valves (e.g. with a history of rheumatic fever) or can occur on normal valves in people who abuse intravenous drugs using contaminated needles or non-sterile substances.
One controversial source of clots in the heart is a patent foramen ovale (PFO) — a small hole in the heart that potentially allows blood from the veins to get into the arteries.
PFO's are present in everyone at birth, but close off in about 80 percent of people. This means that about 20 percent of young adults have a PFO as a potential source of a clot.
Treatment for this remains controversial, as the chance of having a stroke from a PFO is quite small. However, for patients with recurrent problems due to a PFO, closure of the hole or use of blood thinners may be helpful.
The Blood Vessels
A variety of diseases of the blood vessels leading to the brain can cause stroke in young adults.
Fibromuscular dysplasia is a condition in which there is thickening of the wall of blood vessels anywhere in the body. When it occurs in the arteries in the neck, alteration of blood flow or small clots can occur.
Arterial dissection causing stroke is a condition that seems most common in people around the age of 40.
The inner lining of the artery tears, leading either to complete blockage of the artery or formation of a clot that can travel into the brain.
Dissection can occur due to trauma to the head or neck, or can occur spontaneously with minor activity such as sneezing or head turning.
The cause of this condition is not entirely clear, and why it occurs most commonly in this age group is unknown.