Cerebrovascular disease incorporates a group of conditions that are categorised by altered brain function as a result of an inadequate blood supply to a specific part of the brain.
The usual cause of this inadequate blood supply is either narrowing of the blood vessels themselves, otherwise known as stenosis, or due to a blockage, or alternatively due to a rupture of a blood vessel leading to a pressure effect.
In all scenarios, the disruption of the blood supply inevitable results in a lack of oxygen to the part of the brain that the blood supply is feeding and this will result in death of individual cells. When nerve cells or neurons die, they do so very quickly – within a matter of minutes and there is no capacity for the brain to regenerate those dead neurons as there is in other parts of the body. And when neurons die the function of the affected part of the brain becomes limited or non-existent.
This is known as a cerebrovascular accident and in laymen’s terms is called a stroke. If the affected part of the brain controls speech for example then the patient loses the ability to talk.
The usual cause of narrowing or stenosis of the blood vessels that feed the brain is a process called atherosclerosis. A great deal of research has been done and continues to be done as to the cause of atherosclerosis and it is fair to say there is conflicting evidence with regards to implicating certain risk factors. Atherosclerosis involves the disruption of the very smooth lining of a blood vessel which is ordinarily lined by some cells called endothelial cells, leading to an inflammatory reaction and the development of a plaque which allows a thrombus or clot to become adherent. This abnormal growth within the blood vessel wall can then become calcified resulting in a permanent narrowing of the blood vessel. So, this in itself can cause a constriction of the blood vessel over a long period of time, but the other scenario is because of its rough surface a further clot or thrombus can develop which then becomes dislodged and gets pushed along with the blood flow to a point downstream where the vessel narrows and the clot then becomes lodged, completely blocking the flow of blood. The process of thrombus formation and its subsequent dislodgement otherwise known as embolus formation is collectively known as a thromboembolic phenomenon and it tends to happen acutely and with dramatic effect. If it blocks a major vessel then a large part of the brain will die and if this is a critical part of the brain such as one that controls breathing then the patient will collapse and die almost immediately. Alternatively, it may affect a part of the brain that controls a major body part such as the movement of an arm or a leg resulting in complete paralysis of that limb, permanently.
Another scenario within regards to cerebrovascular disease is the development of multiple small emboli effecting small areas of the brain over a long period of time leading to a gradual decline in cerebral function and this is manifest as a form of dementia. This latter condition has been given the title of multi-infarct dementia. An infarct being death of tissue.
Importantly one of the major risk factors for cerebrovascular disease is obesity. We are not quite sure of the exact the exact relationship but it may be a secondary phenomena through other risk factors such as hyperlipidaemia (increased levels of bad fats in the blood), and type 2 diabetes, both of which are more common in patients who are either overweight or suffering from obesity. Whatever the mechanism it is clearly important once again that as individuals we reduce our risk of developing the disease and its sequelae through the management of obesity.