A stroke occurs when the brain does not get the blood and oxygen it needs to function normally. Sometimes it is obvious a person is having a stroke based on the symptoms being experienced. At other times the symptoms may be subtle. In some cases there can be a silent stroke that occurs without causing any symptoms at all. If there are risk factors for a stroke present, understanding the causes of a silent stroke can help to prevent complications.
Narrowed Arteries
The causes of a silent stroke are the same as for other strokes. About 87 percent of all strokes are ischemic, states the American Stroke Association. This type of stroke can be the result of coronary artery disease. CAD is diagnosed when plaque or fatty deposits build up along the walls of the arteries that supply the brain with blood and oxygen. This narrows the artery and reduces blood flow. When the brain is deprived of blood and oxygen, cells can die and a stroke may occur. In cases of a silent stroke, there may be no symptoms or very subtle symptoms, however, images of the brain will show damage. Due to this fact, the ASA suggests that any changes in mental functioning or alertness, no matter how minor, should always be evaluated.
Blockages and Clots
Ischemic strokes can also be caused by a clot. When plaque builds up on the artery walls, there is a risk that pieces of plaque will break off and form a clot, explains the Mayo Clinic. The clot can lodge wherever it broke off or it can travel through the bloodstream and lodge somewhere else in the body. A thrombotic stroke occurs when the clot lodges in the carotid arteries in the neck or in an artery within the brain. This blocks blood and oxygen from getting to the brain and can cause a stroke. Any symptoms such as weakness on one side of the body, trouble speaking or understanding speech, or changes in vision may signal that a silent stroke occurred, according to the ASA.
Ruptures
Any unexplained changes in mood, behavior or memory should be investigated, as these may be signs that a silent stroke occurred. Another cause of silent strokes is hemorrhaging from a ruptured or leaking blood vessel in the brain, according to a 2001 article in the "Journal of the American Medical Association." Approximately 13 percent of all strokes are hemorrhagic strokes. For reasons not well understood, blood vessels in the brain can weaken, develop aneurysms or become abnormally shaped. This can lead to the blood vessel rupturing. The leaking blood can place pressure on the brain and cause a stroke.
