Stroke - Causes of the Disease

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Stroke. Causes

This is how a stroke develops

The following different types of stroke are differentiated depending on their cause:

Inadequate blood supply to the brain: In approx. 80 per cent of cases there is a blockage in a cerebral blood vessel, caused for instance by a blood clot. This causes inadequate blood circulation (ischaemia). This means that the supply of blood and oxygen is no longer adequate to certain regions of the brain. If the symptoms are transitory in nature then in most cases this is referred to as a transitory ischaemic attack (TIA). Here too rapid medical clarification is needed as there is a real fear that other circulatory problems may occur. Vascular occlusions arise because of the transportation of blood clots (embolisms), or because of localised vascular occlusion in the afferent arteries (arterial thrombosis ). In the case of a microangiopathy, changes in the small arteries in the inner brain cause less damage to the brain tissue
Cerebral haemorrhages: In approx. 20 per cent of cases a stroke can also be caused by cerebral haemorrhages. When this happens blood penetrates at high pressure into the surrounding tissue of the brain from burst vessels, which have usually been damaged previously by arterial calcification. The cause is usually high blood pressure or a sudden tear in an artery.
Subarachnoid haemorrhages: Two to five per cent of strokes are induced by subarachnoid haemorrhages. When this occurs there is bleeding into the space between the brain and the soft meninges (arachnoidea). This so-called subarachnoid space is normally filled with cerebral fluid.
More uncommon causes: These may be inflammation of the vessels, spontaneous injuries or trauma to the vessels disorders of the coagulation system or the formation of clots in the venous sinuses ( sinus venous thrombosis).

Other causes of a stroke: Arteriosclerosis

Ischaemic attacks can occur because of a blockage in a cerebral blood vessel because of arterial calcification (arteriosclerosis) on the inner walls of the vessel. This makes the vessel even more tightly occluded with severe restriction or even complete interruption of the blood flow to the brain.

Other causes of a stroke: Thromboses

Vascular occlusion however can also be caused by a thrombosis. This occurs when as a result of arteriosclerosis a vessel wall ruptures. Then through the activation of the body's own blood coagulation system, platelets (thrombocytes) gather at the site of the wound for purposes of agglutination by adhering to one another. This blood clot or platelet plug (thrombus) thus formed increases in size until it completely blocks the vessel.

Other causes of a stroke: Embolisms

Another cause for arterial occlusion can be an embolism. When this occurs a blood clot breaks free somewhere in the body and is carried to the brain in the blood stream. It can easily penetrate into the small vessels and get lodged there. The most common site for the formation of blood clots is the heart. Dysrhythmias, a fresh cardiac infarction, enlargement of the heart cavities, changes in the heart valves and a congenital hole in the septum of the heart are risk factors for the formation of blood clots. If the blockage in the vessel is not broken up in the first few hours, then the part of the brain supplied by the artery will die irrecoverably. Both the main cerebral arteries, which are approx. 2 - 5 mm thick and also their branches of only 1 mm diameter or less can be affected by an arterial occlusion. A blood clot does not need to be big to block an artery and cause a stroke.

Other causes of a stroke: Cerebral haemorrhage

Cerebral haemorrhages occur because an artery bursts in the brain. The most frequent cause is continually high blood pressure over a long period of time, which has caused the small arteries in the brain to become stiff and brittle. They can no longer bear the pressure and they burst. Other possible causes are congenital areas of weakness in the vessels and disorders of blood coagulation.

Other causes of a stroke: Haemorrhages outside the brain

Sometimes haemorrhages can also occur outside the brain and within the skull (subarachnoid haemorrhage). The most common cause are swellings (aneurysms) at damaged areas in the blood vessels mostly as a result of arteriosclerosis. They become increasingly bigger with the danger of bursting and causing internal bleeding. These 'bulges' usually cause no symptoms. Often they have been there for a long period of time already and are frequently only discovered by chance during a routine examination.

Risk factors for a stroke

Anyone can have a stroke. However the risk increases with advancing age. About half of all strokes affect patients over 75 years of age. There are certain risk factors which cannot be changed such as gender (men are more at risk than women), age or hereditary disposition. Other circumstances on the other hand can certainly be influenced or changed. If several of these factors concur, then the risk is even higher.