A stroke in a young person, typically defined as someone under the age of 45 or 50, often has causes that differ significantly from those seen in older adults. While strokes in the elderly are usually linked to long-term atherosclerosis—the hardening and narrowing of arteries—strokes in the young frequently result from underlying structural defects, specific blood disorders, or external factors. Understanding these unique causes is crucial for accurate diagnosis and targeted prevention.
Structural and Cardiac Causes
Physical abnormalities within the blood vessels or the heart structure are frequent causes of stroke in younger individuals. Cervical artery dissection (CAD) is a leading independent cause of ischemic stroke in this group, accounting for approximately 20% to 25% of all cases. This condition involves a tear in the inner lining of one of the four main arteries supplying the brain—the carotid or vertebral arteries. Blood enters the wall and forms a clot, which can block the artery or send fragments to the brain, causing an ischemic stroke.
The tear often occurs spontaneously or following minor trauma, such as a sudden neck movement, chiropractic manipulation, or vigorous coughing. Underlying connective tissue disorders, which weaken the arterial wall, can predispose a person to dissection even without significant external force.
Another structural cause originates in the heart: Patent Foramen Ovale (PFO). This is a small opening between the upper chambers of the heart that failed to close after birth. Although a PFO is present in about one-quarter of the general population, it is found in around 50% of young adults experiencing a cryptogenic stroke—one without a clear cause.
The PFO allows venous blood, potentially containing a clot from elsewhere in the body, to pass directly from the right side of the heart to the left side without being filtered by the lungs. This process, called paradoxical embolism, sends the clot straight into the arterial circulation, where it can travel to the brain. Inflammation of the blood vessel walls, known as vasculitis, can also cause structural damage. Vasculitis narrows the vessels, restricting blood flow, or leads to the formation of a clot that causes an ischemic stroke.
Blood Clotting Disorders
Conditions that make the blood abnormally prone to clotting, independent of vessel damage, are a major category of stroke causes in the young. These disorders are known as hypercoagulable states or thrombophilias, which can be inherited genetically. The Factor V Leiden mutation is one of the most common inherited forms, making a protein involved in the clotting cascade resistant to breakdown and increasing clot risk. Deficiencies in natural anticoagulant proteins, such as Protein C or Protein S, similarly disrupt the body’s ability to regulate clotting, leading to a higher likelihood of clot formation.
Acquired hypercoagulable states also pose a threat, with Antiphospholipid Syndrome (APS) being a prominent example. APS is an autoimmune disorder where the body produces antibodies that mistakenly attack certain proteins, leading to widespread and recurrent blood clots in both arteries and veins. This syndrome can account for up to 20% of stroke events in patients under 45 years of age. The presence of these autoantibodies creates a prothrombotic environment, making the blood prone to forming clots that travel to the brain.
Hormonal factors also alter the blood’s clotting ability, particularly in young women. High-dose oral contraceptives, especially those containing higher levels of estrogen, are known to increase the risk of blood clots. This risk is amplified when the medication is combined with other underlying risk factors, such as smoking or an undiagnosed inherited thrombophilia. These hormonal influences are often implicated in causing cerebral venous thrombosis, a clot in the brain’s draining veins, rather than an artery.
Acquired and Inflammatory Risk Factors
Beyond structural or inherent clotting problems, several external and systemic factors acquired during life can directly trigger or accelerate stroke risk in younger individuals. Substance use, particularly of illicit stimulant drugs, is a recognized cause of stroke in this population. Cocaine and amphetamines induce a sudden and severe spike in blood pressure, which can lead to hemorrhagic stroke due to a burst blood vessel. These substances also cause vasospasm, a sudden narrowing of blood vessels, which can cut off blood flow and result in an ischemic stroke.
Systemic inflammatory and autoimmune diseases can also raise the risk by affecting the blood vessels and coagulation system. Conditions like Systemic Lupus Erythematosus (SLE) are linked to stroke, often because they can cause secondary Antiphospholipid Syndrome. Certain types of migraines, particularly those accompanied by an aura, are associated with an increased risk of stroke, especially in young women who smoke or use oral contraceptives. While not a direct cause, the migraine may indicate an underlying vascular susceptibility.
Traditional vascular risk factors, such as high blood pressure, diabetes, and elevated cholesterol, are also increasingly contributing to stroke in the young. Though typically associated with older patients, poor control of these conditions in youth accelerates damage to the arterial walls. This accelerated vascular aging, often driven by factors like obesity and poor diet, makes the younger patient’s vessels more vulnerable to the specific mechanisms of stroke mentioned previously. Aggressive management of these common conditions is a component of stroke prevention for the younger generation.