Stroke / Cerebrovascular Disorders

The word cerebrovascular is made up of two parts – “cerebro” which refers to the large part of the brain, and “vascular” which means arteries and veins. Together, the word cerebrovascular refers to blood flow in the brain. The term cerebrovascular disease includes all disorders in which an area of the brain is temporarily or permanently affected by ischemia or bleeding and one or more of the cerebral blood vessels are involved in the pathological process. Cerebrovascular disease includes stroke, carotid stenosis, vertebral stenosis and intracranial stenosis, aneurysms, and vascular malformations.

Restrictions in blood flow may occur from vessel narrowing (stenosis), clot formation (thrombosis), blockage (embolism) or blood vessel rupture (hemorrhage). Lack of sufficient blood flow (ischemia) affects brain tissue and may cause a stroke.

Blood Flow to the Brain

The heart pumps blood up to the brain through two sets of arteries, the carotid arteries and the vertebral arteries. The carotid arteries are located in the front of the neck and are what you feel when you take your pulse just under your jaw. The carotid arteries split into the external and internal arteries near the top of the neck with the external carotid arteries supplying blood to the face and the internal carotid arteries going into the skull. Inside the skull, the internal carotid arteries branch into two large arteries – the anterior cerebral and middle cerebral arteries and several smaller arteries – the ophthalmic, posterior communicating and anterior choroidal arteries. These arteries supply blood to the front two-thirds of the brain.

The vertebral arteries extend along side the spinal column and cannot be felt from the outside. The vertebral arteries join to form a single basilar artery near the brain stem, which is located near the base of the skull. The vertebrobasilar system sends many small branches into the brain stem and branches off to form the posterior cerebellar and posterior meningeal arteries, which supply the back third of the brain. The jugular and other veins carry blood out of the brain.

Because the brain relies on only two sets of major arteries for its blood supply, it is very important that these arteries are healthy. Often, the underlying cause of an ischemic stroke is carotid arteries blocked with a fatty buildup, called plaque. During a hemorrhagic stroke, an artery in or on the surface of the brain has ruptured or leaks, causing bleeding and damage in or around the brain.

Whatever the underlying condition and cause are, it is crucial that proper blood flow and oxygen be restored to the brain as soon as possible. Without oxygen and important nutrients, the affected brain cells are either damaged or die within a few minutes. Once brain cells die, they cannot regenerate, and devastating damage may occur, sometimes resulting in physical, cognitive and mental disabilities.

Stroke

Stroke is an abrupt interruption of constant blood flow to the brain that causes loss of neurological function. The interruption of blood flow can be caused by a blockage, leading to the more common ischemic stroke, or by bleeding in the brain, leading to the more deadly hemorrhagic stroke. Ischemic stroke constitutes an estimated 80 percent of all stroke cases. Stroke may occur suddenly, sometimes with little or no warning, and the results can be devastating.

Stroke Symptoms

Warning signs may include some or all of the following symptoms, which are usually sudden:

• Dizziness, nausea, or vomiting
• Unusually severe headache
• Confusion, disorientation or memory loss
• Numbness, weakness in an arm, leg or the face, especially on one side
• Abnormal or slurred speech
• Difficulty with comprehension
• Loss of vision or difficulty seeing
• Loss of balance, coordination or the ability to walk

Types of Stroke and Treatment

Ischemic Stroke
Ischemic stroke is by far the most common type of stroke, accounting for a large majority of strokes. There are two types of ischemic stroke: thrombotic and embolic. A thrombotic stroke occurs when a blood clot, called a thrombus, blocks an artery to the brain and stops blood flow. An embolic stroke occurs when a piece of plaque or thrombus travels from its original site and blocks an artery downstream. The material that has moved is called an embolus. How much of the brain is damaged or affected depends on exactly how far downstream in the artery the blockage occurs.

In most cases, the carotid or vertebral arteries do not become completely blocked and a small stream of blood trickles to the brain. The reduced blood flow to the brain starves the cells of nutrients and quickly leads to a malfunctioning of the cells. As a part of the brain stops functioning, symptoms of a stroke occur. During a stroke, there is a core area where blood is almost completely cut off and the cells die within five minutes. However, there is a much larger area known as the ischemic penumbra that surrounds the core of dead cells. The ischemic penumbra consists of cells that are impaired and cannot function, but are still alive. These cells are called idling cells, and they can survive in this state for about three hours.

Ischemic stroke is treated by removing the obstruction and restoring blood flow to the brain. One treatment for ischemic stroke is the FDA-approved drug, tissue plasminogen activator (tPA), which must be administered within a three-hour window from the onset of symptoms to work best. Unfortunately, only 3 to 5 percent of those who suffer a stroke reach the hospital in time to be considered for this treatment. This medication carries a risk for increased intracranial hemorrhage and is not used for hemorrhagic stroke. For patients beyond the three-hour time window, intrarterial thrombolysis with drugs or mechanical devices may be an option. Carotid endarterctomy, and or stenting of the cervical and intracranial vessels, may help reduce recurrent stroke in some cases.

The Merci Retriever, approved recently by the FDA, is a corkscrew-shaped device used to help remove blood clots from the arteries of stroke patients. A small incision is made in the patient’s groin, into which a small catheter is fed until it reaches the arteries in the neck. At the neck, a small catheter inside the larger catheter is guided through the arteries until it reaches the brain clot. The Merci Retriever, a straight wire inside the small catheter pokes out beyond the clot and automatically coils into a corkscrew shape. It is pulled back into the clot, the corkscrew spinning and grabbing the clot. A balloon inflates in the neck artery, cutting off blood flow, so the device can pull the clot out of the brain safely. The clot is removed through the catheter with a syringe.

Hemorrhagic Stroke
A hemorrhagic stroke can be caused by hypertension, rupture of an aneurysm or vascular malformation or as a complication of anticoagulation medications. An intracerebral hemorrhage occurs when there is bleeding directly into the brain tissue, which often forms a clot within the brain. A subarachnoid hemorrhage occurs when the bleeding fills the cerebrospinal fluid spaces around the brain. Both conditions are very serious.

Hemorrhagic stroke usually requires surgery to relieve intracranial (within the skull) pressure caused by bleeding. Surgical treatment for hemorrhagic stroke caused by an aneurysm or defective blood vessel can prevent additional strokes. Surgery may be performed to seal off the defective blood vessel and redirect blood flow to other vessels that supply blood to the same region of the brain.

Endovascular treatment involves inserting a long, thin, flexible tube (catheter) into a major artery, usually in the thigh, guiding it to the aneurysm or the defective blood vessel and inserting tiny platinum coils (called stents) into the blood vessel through the catheter. Stents support the blood vessel to prevent further damage and additional strokes.

Recovery and rehabilitation are important aspects of stroke treatment. In some cases, undamaged areas of the brain may be able to perform functions that were lost when the stroke occurred. Rehabilitation includes physical therapy, speech therapy and occupational therapy.

Regardless of what type of stroke has been suffered, it is critical that victims receive emergency medical treatment as soon as possible for the best possible outcome to be realized. By learning the signs and symptoms of stroke and treating risk factors preventively, it is possible to help avert the devastating results of this disease.

Transient Ischemic Attack (TIA)
A TIA is a temporary cerebrovascular event that leaves no permanent damage. Most likely an artery to the brain is temporarily blocked, causing stroke-like symptoms, but the blockage dislodges before any permanent damage occurs.

Symptoms of a TIA may be similar to stroke, but they resolve quickly. In fact, symptoms may be so vague and fleeting that people just “brush” them off, especially when they last just a few minutes. TIA symptoms include:

• Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• Sudden confusion, trouble speaking or understanding
• Sudden trouble seeing in one or both eyes
• Sudden trouble walking, dizziness, loss of balance or coordination
• Sudden, severe headache with no known cause

While there is no treatment for the TIA itself, it is essential that the source of the TIA be identified and appropriately treated before another attack occurs. If you experience TIA symptoms, seek emergency medical help and notify your primary care physician immediately. About 30 percent of all people who suffer a major stroke experience a prior TIA, and 10 percent of all TIA victims suffer a stroke within two weeks. The quicker you seek medical attention, the sooner a diagnosis can be made and a course of treatment started. Early intervention is essential to effectively preventing a major stroke. Treatment options for TIA patients focus on treating carotid artery disease or cardiac problems.

Risk Factors

Although they are more common in older adults, strokes can occur at any age. Stroke prevention can help reduce disability and death caused by the disease. Controllable or treatable risk factors for stroke include:

• Smoking: Decrease risk by quitting smoking. Risk may be increased further with the use some forms of oral contraceptives and are a smoker. There is recent evidence that long-term secondhand smoke exposure may increase the risk of stroke.
• High blood pressure: Blood pressure of 140/90 mm Hg or higher is the most important risk factor for stroke. Controlling blood pressure is crucial to stroke prevention.
• Carotid or other artery disease: The carotid arteries in the neck supply blood to the brain. A carotid artery narrowed by fatty deposits from atherosclerosis (plaque buildups in artery walls) may become blocked by a blood clot.
• History of transient ischemic attacks (TIAs).
• Diabetes: It is crucial to control blood sugar levels, blood pressure and cholesterol levels. Diabetes, especially when untreated, puts one at greater risk of stroke and has many other serious health implications.
• High blood cholesterol: A high level of total cholesterol in the blood (240 mg/dL or higher) is a major risk factor for heart disease, which raises the risk of stroke.
• Physical inactivity and obesity: Being inactive, obese or both can increase the risk of high blood pressure, high blood cholesterol, diabetes, heart disease and stroke.
• Recent research shows evidence that people receiving hormone replacement therapy (HRT) have an overall 29 percent increased risk of stroke, in particular ischemic stroke.

Uncontrollable risk factors include:

• Age: People of all ages, including children, have strokes. But the older you are, the greater your risk of stroke.
• Gender: Stroke is more common in men than in women.
• Heredity and race: There is a greater risk of stroke if a parent, grandparent, sister or brother has had a stroke. Blacks have a much higher risk of death from a stroke than Caucasians do, partly because they are more prone to having high blood pressure, diabetes and obesity.
• Prior stroke or heart attack: Those who have had a stroke are at much higher risk of having another one. Those who have had a heart attack are also at higher risk of having a stroke.

Source: https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Cerebrovascular-Disease