Endovascular Neurosurgery

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ENDOVASCULAR NEUROSURGERY

Brain Ischemia
(Stroke)

The brain needs a certain amount of blood delivered to it in order to function properly and survive. If this amount is diminished it can cause temporary or permanent brain dysfunction and several problems are manifested.

Their severity and duration depends on the amount of blood delivered in relation to that needed and on the duration of this disorder in blood supply. The more the blood supply is diminished and the longer this condition lasts the more probable is the permanent damage of the brain.

This low blood supply can affect the whole of the brain as in severe hypotension or cardiac arrest or it can affect certain parts of it. The reason for local brain ischemia is usually a stenosis or a complete block of one of the main arteries or one of its branches which supply blood to the brain. The main causes for this stenosis or blocking of arteries are:

1. Atherosclerosis, a disease mainly caused by hyperlipidemia and heavy smoking, which leads to gradual stenosis (narrowing) of the arteries.

2. Embolism, when a blood clot or a fragment from an atherosclerotic plaque travelling in the arterial system cannot pass through an artery smaller than its size and it blocks it. These blood clots or emboli are formed folowing some heart diseases or coagulation disorders.

3. Thrombosis, when a blood clot is formed directly inside the artery. Thrombosis can be caused by various conditions like arteritis (inflammation of an artery, coagulation disorders, slow blood flow, foreign bodies inside an artery or direct trauma to it.

4. Vasospasm, a condition of active spasm and narrowing of the arteries. It usually follows subarachnoid hemorrhage. Very often vasospasm is a serious complication of this disease.

The reduction in blood supply to a certain part of the brain can cause the following syndromes:

1. Transient Ischemic Attacks (TIAs). They are characterised by a focal neurological deficit which lasts no more than 24 hours. The kind of deficit depends on the area of the brain affected and can be a dysfunction of memory, speech, vision, movement or sensation. They are usually caused by stenosis or vasospasm in an artery which under certain conditions results in a reduction to blood supply compared to the amount needed.The condition returns to normal when the supply is increased.

2. Reversible Ischemic Neurologic Deficit (RIND). It is also a focal neurological defition like the ones mentioned above but returns to normal later than 24 hours and within a few days. It can have the same causes as the TIAs but temporary thrombosis as well.

3. Ischemic Stroke. It is a necrosis of a part of the brain and is characterized by a permanent neurologic deficit caused by prolonged reduction or complete arrest of blood supply to an area of the brain. It can be caused by the same factors as TIAs and RINDs but by arterial embolism as well.

4. Progressing Stroke. It is characterized by the addition of more focal neurological deficits over the next few hours or days following the initial insult. It is usually caused by a thrombosis which progresses and extends to include more arteries or by multiple emboli.

Neurons in completely ischemic brain tissue soon die. Around the center of this area exists a zone called the penumbra which contains neurons in semiviable condition because the blood supply in it is reduced but not so much that it would cause their death. The target of stroke therapy is to resupply the penubra with enough oxygen to help at least these neurons survive.

The ways to accomplish this aim are reopening of the stenosed or occluded arteries and controlling various properties of the blood like its pressure, oxygen content, coagulation etc.

Endovascular Neurosurgery offers excellent results in accomplishing the reopening of the arteries and treating stenosis, embolism, thrombosis and vasospasm.

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Page maintained by: Vasilis Katsaridis, MD