A stroke is permanent malfunction of the brain caused by a problem with the brains blood vessels. Each organ of the body has blood vessels circulating blood via high pressure arteries conveying the good things for life (oxygen, sugar, etc.) and linking via the smallest vessels called capillaries to low pressure veins that return the blood (and waste products such as C02) to the heart.
Most strokes occur in old age as a result of a blood vessel of the brain blocking-off due to wear and tear processes but acute thrombosis (blood clot formation) can occur on the arterial or venous side of the circulation. A thrombosis elsewhere in the body (carotid artery) can travel to the brain but it is rare for a peripheral deep vein thrombosis (DVT) to cause a stroke unless the patient has a hole in their heart (patent ductus arteriosus, PDA).
If a young person has a stroke this usually is linked to a problem that they have been born with (congenital). A baby can develop a stroke form an aneurysm of the Vein of Galen; a teenager can bleed from a birth mark on the brain and young adults can suffer bleeding (subarachnoid haemorrhage, SAH) from an aneurysm (blister) on a brain artery.
Congenital reasons for vascular abnormalities are rare. An abnormal connection between an artery(A) and a vein(V), without the intervening capillary network, is called a (AV) fistula. They can cause brain malfunction by direct pressure or water on the brain (hydrocephalous) or even short-circuit so much blood the heart can fail.
A birth-mark on the brain with a knot of small arterial and venous blood vessels (nidus) with no intervening brain tissue is called an AM malformation (AVM). These remain silent for most people but can cause bleeding at any stage in life.
A birth-mark of the capillaries is termed a cavernous angioma (cavernoma) which again usually remains silent but cause a low pressure bleed leading to headaches or even seizures.
An aneurysm on the brains’ arteries is like a berry in size and shape but can be as small as a redcurrant or as large as a strawberry. People may be born with a blood vessel wall weakness but it can take decades of wear and tear before the aneurysm bursts causing bleed typically into the fluid compartment around the brain which is beneath a layer of meninges called the arachnoid membrane (SAH).
A thrombosis of the veins of the brain can occur in patients with blood clotting abnormalities which they may be born with or secondary to problems such as dehydration. If the veins clot, then the blood can’t flow causing a build-up of pressure and even bleeding.
A fistula (abnormal connection between an artery and vein) can develop over time due to damage to the blood vessels and lead to high venous pressure and bleeding.
Hardening of the arteries occurs as a result of aging but is accelerated in people with risk factors such as smoking, high blood pressure, high cholesterol and poorly controlled diabetes. If the arteries crack this causes inflammation and the clotting of blood. This can lead to the solid particles breaking free (embolism) and then blocking smaller arteries downstream in the brain. A blocked artery causes the brain supplied by that artery to die (ischaemia) which is the normal reason for a stroke (90%) but sometimes the dead part of the brain then bleeds (haemorrhagic stroke) causing more problems.
A person suffering a stroke normally has sudden problems with moving part of their body (face, arm or leg), their speech or balance. If there is a bleed, then headache is typical and so may the level of consciousness. In SAH the headache is typically very sudden and severe.
It is vital that patients get to hospital quickly because a lot of treatments are time dependent. A clinical assessment and brain scan is needed.
If a blood clot has formed in an artery and brain cells are dying it is imperative to bust that blood clot with blood thinning agents that may need to be delivered into the brain arteries (endovascular).
If the patient has raised intracranial pressure (ICP) then surgery may be required to relieve that pressure.
All patients with the diagnosis of a stroke need careful medical and nursing care to help them recover and prevent further upsets to the brain from low blood pressure, poor blood sugar control, etc. (secondary insults).
In those patients that survive a bleed, the bleeding has stopped before getting to hospital. AVMs, fistulae and aneurysm need special blood vessel scans and x-rays (angiograms) to see them. Cavernomas are not visible on angiograms but need an MRI scan to detect them.
In order to prevent a further bleed treatment may need in the form of endovascular occlusion from inside the brains blood vessels (coiling); microsurgical clipping with an operation (clipping) or focussed radiotherapy (stereotactic radiosurgery, SRS).
Patients unable to go home after their stroke will need a period of rehabilitation to maximise their recovery with the help of physiotherapists, speech therapists and occupational therapists
Improved detection of vascular abnormalities and heathy life-style advice will reduce the number of strokes. Faster management and more minimally invasive treatments will improve outcomes.
If you are concerned about the health of your blood vessels it is important to have regular checks with your GP to rule out risk factors. If there is on-going concern due to symptoms or family history a specialist assessment is advised.