The brain receives its blood supply from four main arteries: the two internal carotid arteriesThe two carotid arteries are located on each side of the front of the neck. These arteries provide the principal blood supply from the heart to the head and neck. and the two vertebral arteriesThe two vertebral arteries follow the vertebral column at the back of the neck. They carry blood from the heart to the brain.. The clinical consequences of vascular disease in the cerebral circulation will depend upon which vessels or combinations of vessels are involved.
The following situations can occur:
Stroke: Stroke occurs when the blood supply to a part of the brain is blocked resulting in the death of an area within the brain. If a large vessel is blocked the outcome may be rapidly fatal or may lead to very severe disability. If smaller blood vessels are blocked the outcome is less severe and recovery may be good. The most common types of disability are the loss of use of one side of the body and speech problems.
There are three principal types of stroke:
The thrombotic and haemorrhagic forms are the most common, although they occur with varying frequency worldwide.
Transient ischaemic attack: Transient ischaemic attacks arise when the blood supply to a part of the brain is temporarily interrupted without producing permanent damage. By definition, recovery occurs within 24 hours. These attacks, particularly if frequent, can be a warning sign of an impending stroke. They usually result from small blood clots or clumps from plaques of atheroma which get carried into the blood circulation producing transient blockages. Occasionally these clots may get carried from the heart or arteries leading to the brain (e.g. carotid arteries), rather than from within the cerebral circulation itself.
Dementia: This may result from repeated episodes of small strokes which produce progressive damage to the brain over a period of time. The main clinical feature of dementia is a gradual loss of memory and intellectual capacity. Loss of motor function in the limbs and incontinence can also occur.
Cerebrovascular disease mortality has also declined markedly in many developed countries during the last half of the twentieth century. In developing countries and in the former Soviet Union, rates appear to have shot up. They are certainly much higher in many developing countries now than in developed countries. However historical data are lacking to confirm these trends.
As well as a difference in total trends, there are also differences in the relative frequencies of the type of stroke in different parts of the world. In Japan and China for example the haemorrhagic form accounts for a higher proportion of cases than is seen in the West. The relative frequency of the thrombotic form of stroke appears to mirror the prevalence of coronary heart disease. However, reliable data on the worldwide occurrence of each type of stroke are not available.
The charts below provide information on cerebrovascular disease mortality from all types of stroke. It is necessary to use mortality data for international comparisons because incidence data are available for too few countries.
| Country | Mortality (per 100,000 population per year) |
|---|---|
| Kyrgyzstan |  365.1 |
| Russian Federation | 336.5 |
| Kazakhstan | 307.1 |
| Latvia | 290.7 |
| Moldova, Republic of | 281.8 |
| Romania | 278.9 |
| Belarus, Republic of | 278.9 |
| Guyana | 275.0 |
| Yugoslavia | 271.5 |
| Ukraine | 262.8 |
| Country | Mortality (per 100,000 population per year) |
|---|---|
| Kyrgyzstan | 258.9 |
| Samoa | 256.1 |
| St Kitts and Nevis | 255.6 |
| Moldova, Republic of | 225.1 |
| Russian Federation | 212.8 |
| Kazakhstan | 210.0 |
| Yugoslavia | 208.5 |
| Guyana | 197.2 |
| Romania | 184.3 |
| Uzbekistan | 179.6 |