Transient Ischemic Attack (TIA, Mini-Stroke) (cont.)

The primary role of the brain is to send signals to the body for motor function and to receive signals through the five senses (sight, hearing, touch, smell, and taste), and to respond to them. The brain processes information through conscious thought, and unconsciously through nerve systems that control basic bodily functions, like heart rate, breathing, and temperature control.

In simple terms:

• The brain is arranged so that the right side of the brain controls the left side of the body, and the left side of the brain controls the right of the body.
• Vision is located in the back of the brain (occiput), and balance and coordination are located at the bottom of the brain (cerebellum).
• Blood supply to the brain comes from the carotid arteries that are located in the front of the neck, and the vertebral arteries that run in the back of the neck through small canals in the bony spine (vertebrae) of the neck.
• All of these connect at a junction of blood vessels located in the base of the brain (called the Circle of Willis), and from there smaller arteries supply the brain with oxygen and nutrients.

When a portion of the brain loses its blood supply, it can become damaged and stop functioning. When a portion of the brain does not function, the part of the body that it controls also stops working. This is called a stroke or a cerebrovascular accident (CVA). If the brain is able to regain its blood supply quickly, then the CVA symptoms may resolve; this is known as a transient ischemic attack (TIA). A TIA is similar to a stroke that resolves by itself because of a temporary lack of oxygen to a portion of the brain.

Loss of blood supply to portions of the brain can occur for a variety of reasons. A blood vessel can become blocked, and blood supply to a part of the brain is lost, or a blood vessel can leak blood into the brain (brain hemorrhage). Most commonly however, the blood vessel is blocked. The blockage can be caused by a blood clot that forms in the blood vessel (thrombosis) or it can be caused by a clot or debris that floats downstream (embolus).

Blocked blood vessels

Fatty plaque formation in the blood vessel wall is called atherosclerosis or "hardening of the arteries." Plaque can rupture and cause a small blood clot to form and occlude the blood vessel. Blockage can also occur when debris from narrowing of a carotid artery breaks off, and floats downstream to cause the occlusion. Sometimes, in people with an irregular heart beat called atrial fibrillation, small blood clots can be formed within the heart and travel to the brain to cause the obstruction.

Picture of Carotid Artery Disease and Plaque Buildup

Brain hemorrhage or bleeding in the brain can be due to an aneurysm, a weak spot in a blood vessel that ruptures and spills blood into the brain tissue, or it may be due to spontaneous bleeding caused by poorly controlled hypertension (high blood pressure). Such bleeding more commonly results in the irreversible damage of a stroke, as opposed to a TIA.

Source: MedicineNet.com
http://www.medicinenet.com/transient_ischemic_attack_tia_mini-stroke/article.htm