Dr. Ajaya N Jha
Chairmannstitute of Neurosciences
Types of stroke
It occurs when an artery to the brain is blocked. The brain depends on its arteries to bring fresh blood from the heart and lungs. The blood carries oxygen and nutrients to the brain and takes away carbon dioxide and cellular waste. If an artery is blocked, the brain cells (neurons) cannot make enough energy and will eventually stop working. If the artery remains blocked for more than a few minutes, the brain cells may die. This is why immediate medical treatment is critical.
Ischemic stroke can be caused by several different kinds of diseases. The most common problem is narrowing of the arteries in the neck or head. This is most often caused by atherosclerosis or gradual cholesterol deposition. If the arteries become too narrow, blood cells may collect and form blood clots. These blood clots can block the artery where they are formed (thrombosis) or can dislodge and become trapped in arteries closer to the brain (embolism). Another cause of stroke is blood clots in the heart, which can occur as a result of irregular heartbeat (for example, atrial fibrillation), heart attack or abnormalities of the heart valves. While these are the most common causes of ischemic stroke, there are many other possible causes. Examples include use of street drugs, traumatic injury to the blood vessels of the neck or disorders of blood clotting.
Ischemic stroke can be divided into two main types: Thrombotic and Embolic.
A thrombotic stroke occurs when diseased or damaged cerebral arteries become blocked by the formation of a blood clot within the brain. The process leading to this blockage is known as thrombosis. Strokes caused in this way are called thrombotic strokes. That's because the medical word for a clot that forms on a blood-vessel deposit is thrombus.
Blood-clot strokes can also happen as the result of unhealthy blood vessels clogged with a build-up of fatty deposits and cholesterol. Your body regards these build-ups as multiple, tiny and repeated injuries to the blood vessel wall. So your body reacts to these injuries just as it would if you were bleeding from a wound; it responds by forming clots.
Two types of thrombosis can cause stroke: large vessel thrombosis and small vessel disease (or lacunar infarction).
Thrombotic stroke occurs most often in the large arteries, so large vessel thrombosis is the most common and best understood type of thrombotic stroke. Most large vessel thrombosis is caused by a combination of long-term atherosclerosis followed by rapid blood clot formation. Thrombotic stroke patients are also likely to have coronary artery disease and heart attack is a frequent cause of death in patients who have suffered this type of brain attack.
Small Vessel Disease/Lacunar Infarction occurs when blood flow is blocked to a very small arterial vessel. The term's origin is from the Latin word lacuna which means hole and describes the small cavity remaining after the products of deep infarct have been removed by other cells in the body. Little is known about the causes of small vessel disease, but it is closely linked to hypertension (high blood pressure).
An embolic stroke is also caused by a clot within an artery. In an embolic stroke, a blood clot forms somewhere in the body (usually the heart) and travels through the bloodstream to your brain. Once in your brain, the clot eventually travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke. The medical word for this type of blood clot is embolus.
The following table indicates similarities and differences of both types of Ischemic Attacks
A transient ischemic attack (TIA) is defined as a sudden onset of any focal neurological dysfunction affecting vision, speech or strength on one side of the body that lasts for few minutes to less than an hour with complete recovery of the symptoms.
TIA's are considered as warning signs of major impending stroke and they warrant urgent neurological consultation. About 1 in 3 people who have a TIA will eventually have a stroke, with about half occurring within a year after the TIA. More than 10% of people who have a TIA will have a stroke within 3 months. Half of these strokes happen during the initial 48 hours after a TIA. Therefore, it is recommended that anyone who has suffered a TIA should see a stroke neurologist within initial 48 hours and get evaluated.
Our clinic runs under the guidance of Stroke neurologist and provides our patients with high speed rapid assessment of TIA's. All the investigations are directed towards identifying the cause of TIA viz. CT Brain with CT Angiography/MRI Brain with MR Angiography, ECG, 2D Echocardiography, Lipid profile, HbA1C for Diabetes, 24-hour Holter monitoring to pick up cardiac rhythm disorders like Atrial Fibrillation including the high-end advanced investigations viz. CT Perfusion studies, MR Perfusion studies, extended Holter monitoring, specialized blood tests to identify blood coagulation disorders and hypercoagulable states, Cerebral Angiography in the Angio suite. The clinic has multidisciplinary approach and has a comprehensive assessment by specialists' viz. Stroke Neurologist, Interventional stroke neuroradiologists, diabetologist, cardiologist, dietician, physical therapist. Clinic also provides treatment of triggers to TIA i.e. Hypertension, Diabetes (Endocrine consultation), high cholesterol, blood thinners (like Aspirin), anticoagulation for cardiac disorders, carotid artery stenting or endarterectomy.
Strokes caused by the breakage or "blowout" of a blood vessel in the brain are called haemorrhagic strokes. The medical word for this type of breakage is haemorrhage.
Haemorrhages can be caused by a number of disorders which affect the blood vessels, including long-standing high blood pressure and cerebral aneurysms. An aneurysm is a weak or thin spot on a blood vessel wall. These weak spots are usually present at birth. Aneurysms develop over a number of years and usually don't cause detectable problems until they break.
There are two types of haemorrhagic stroke: subarachnoid and intracerebral.
In an intracerebral haemorrhage, a blood vessel in the brain bursts and spills into the surrounding brain tissue, damaging brain cells. Brain cells beyond the leak are deprived of blood and damaged. High blood pressure, trauma, vascular malformations, use of blood-thinning medications and other conditions may cause intracerebral haemorrhage.
In a subarachnoid haemorrhage, an artery on or near the surface of your brain bursts and spills into the space between the surface of your brain and your skull. This bleeding is often signalled by a sudden, severe headache. A subarachnoid haemorrhage is commonly caused by the rupture of an aneurysm, a small sack-shaped or berry-shaped out pouching on an artery in the brain. After the haemorrhage, the blood vessels in your brain may widen and narrow erratically (vasospasm), causing brain cell damage by further limiting blood flow to parts of your brain.
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel Aneurysms can commonly occur in arteries at the base of the brain (the circle of Willis) and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart. When the size of an aneurysm increases, there is a significant risk of rupture, resulting in severe haemorrhage, other complications or death.
A person may inherit the tendency to form aneurysms or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled and others can't. The following risk factors may increase your risk of developing an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing:
People who have a family history of brain aneurysms are more likely to have an aneurysm than those who don't.
People who have had a brain aneurysm are more likely to have another.
Women are more likely to develop a brain aneurysm or to suffer a subarachnoid haemorrhage.
The risk of subarachnoid haemorrhage is greater in people with a history of high blood pressure (hypertension).
In addition to being a cause of hypertension, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.
A less common form of haemorrhage stroke is when an arteriovenous malformation (AVM) ruptures. AVM is an abnormal tangle of thin-walled blood vessels that is present at birth.
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