Topic of the Month
Cerebrovascular Disease: Recognition, prevention and treatment
Vascular diseases in the brain, heart and in other parts of the body share common risk factors that include hypertension, diabetes, smoking, hyperlipidemia and a sedentary life style. Unchecked, these risk factors accelerate atherosclerosis leading to occlusions of large and small vessels disease that manifests as cortical and sub-cortical stroke. Aggressive management of risk factors and life-style changes has led to a remarkable decline in the incidence of stroke in the developed world over the last 7 decades, which has not been seen in the low to middle income countries. Worldwide, stroke still remains the second leading cause of death and leading cause of acquired disability and the second most common cause of dementia.
In addition to the risk factors mentioned above, two important ‘high-risk’ conditions require particular attention. The risk of stroke is particularly high in patients with atrial fibrillation. The incidence of atrial fibrillation is rising as the population ages. The lifetime likelihood of suffering a stroke is one in twenty in patients who suffer from atrial fibrillation. This can be significantly decreased with the use of anticoagulation treatments. The second group of patients at a high risk for stroke are those whose initial presentation is with a transient ischemic attack (TIA). This risk is particularly high in the immediate post-TIA time period, particularly in patients with symptomatic carotid stenosis.
There are two common presentation of cerebrovascular disease. Ischemic stroke comprises 80% of cases presenting as cortical and subcortical infarctions depending on the age, genetic and the risk factor profile. The common causes for ischemic stroke include atherosclerotic narrowing of the carotid or vertebral arteries, cardioembolism and lacunar stroke. Cardioembolism is particularly common in patients with atrial fibrillation and rheumatic heart disease. Lacunar stroke occurs in patients with uncontrolled hypertension and diabetes mellitus. Other rare causes of ischemic stroke include, venous thrombosis, stroke related to arterial dissection of the neck vessels, migraine, prothrombotic disorders and the use of birth control pills.
Intra-cranial hemorrhage (ICH) comprises the remainder 20% of cases. Of these, approximately 50% are subarachnoid hemorrhage, related to underlying aneurysms. The remainder are intra-cerebral hemorrhages where hypertension, amyloid angiopathy and arteriovenous malformations are common underlying contributing factors.
The hallmark of stroke symptoms is the ‘sudden’ onset and very frequently respecting anatomical distribution of blood vessels. Thus weakness or numbness of one side of the body, speech difficulty, vertigo and vision loss are common presenting symptoms. Headache is not a feature of ischemic stroke but is very frequently associated with brain hemorrhage, especially when the hemorrhage develops in the subarachnoid space. Patients presenting with a hemorrhage may often be drowsy and may have neck stiffness.
The severity of symptoms is quite variable. The duration of neurological deficits in patients with short periods of occlusion of an intracranial artery may be very brief and such symptoms are often not taken seriously by the patient or the medical profession. These ‘transient ischemic attacks (TIAs)’ require urgent work up and treatment as the risk of a recurrent larger stroke is very high in the immediate follow-up time period.
Improvement in medical care over the last five decades has led to a significantly decrease in the mortality in patients with ischemic stroke. The mortality following brain hemorrhage still remains high. Recovery may not be complete and many patients are left with moderate to severe disability following an acute stroke.
It is important to recognise the symptoms of a stroke early. Such patients should be rushed to a treatment facility that has expertise in treating an acute stroke. It is best that the patient be transported in an ambulance. This allows for rapid access to the appropriate hospital and early notification that the ambulance is bringing in a ‘suspected’ stroke allows the hospital to activate the stroke team to the hospital emergency department where urgent evaluation and treatment offers best hope for recovery.
Investigating the etiology of an acute stroke
All patients presenting with sudden onset focal neurological symptoms require imaging of the brain, neck and brain arteries and the heart. In some patients, especially younger patients or in whom there is a family history of similar events, additional investigation may be required. Such patients are best seen at hospitals that specialize in the care of stroke patients.
The brain CT or MRI scan is the initial investigation used to determine if the patient has suffered an acute stroke. The differentiation of an ischemic stroke from a brain hemorrhage is essential as the treatment for the two conditions are very different. In addition to identifying the type of stroke, the brain imaging also helps with determining the size of the brain lesion and very frequently may offer clues of the underlying etiology. Many stroke programs require that CT/MRI angiography be part of the acute imaging protocol. This allows for an excellent documentation if there is occlusion of an artery in patients with ischemic stroke or the presence of an aneurysm in patients with subarachnoid hemorrhage.
In addition, monitoring of the cardiac rhythm is important. Atrial fibrillation is a frequent cause of stroke and may be intermittent and missed on a routine examination of EKG. Traditionally 24 hours of continuous recording with a Holter monitor is recommended. Recent research suggests that this may not be sufficient to detect paroxysmal atrial fibrillation as a cause of an acute ischemic stroke. Newer recorders with monitoring capability of 10 days or longer are increasingly being used, especially in patients where the etiology of the stroke is not apparent on the initial investigations.
Prevention and treatment of stroke
The spectacular decline in the incidence of stroke during the last 7 decades is most likely as a result of improvements in lifestyle habits and early recognition and treatment of risk factors for vascular diseases. It is important that regular exercise be made part of the normal daily routine and regular visits to the family doctor include the evaluation of the blood pressure, risk for diabetes, discourage the use of tobacco and determination of serum lipid levels.
It is now 30 years since the initial trials revealed that reperfusion treatment with intravenous tissue plasminogen activator (tPA) was associated with a significantly better outcome in patients presenting early (within 3 hours) following an acute ischemic stroke. Later studies showed that the window for successful treatment with tPA may be up to 4.5 hours. Early treatment with tPA offers better results as brain cells die fast (at a rate of 2 million cells per minute) following an acute ischemic stroke. The treatment can only be offered in specialized stroke centers as it carries a serious risk of brain hemorrhage if not used with appropriate precautions. At the Hamad General Hospital tPA was used to treat 102 patients in 2015 (this is 18% of patients presenting with acute ischemic stroke). The recent introduction of tele-stroke medicine allows for remote treatment of stroke patients at distant sites by experts that are located at the comprehensive stroke center. One such facility was developed at the Al-Khor hospital in Qatar that is closely linked to the stroke program at Hamad General Hospital.
Perhaps the most important advance in management of acute stroke has been the recent introduction of stentrivers for reperfusion in patients with acute stroke. Five large clinical trials published in the New England Journal of Medicine in 2015 showed that the use of such endovascular devices was superior to the use of tPA alone in patient with stroke secondary to occlusion of a large cranial artery. The technology is however expensive and not widely available. Hamad General Hospital has a team of experts that can offer the treatment to the appropriate patients at any time of the day or night (34 patients were treated in a six month period Oct 2015-March 2016).
Currently there is no definitive treatment for patients presenting with an acute intra-cerebral hemorrhage. Such patients are managed symptomatically with attention to better management of the blood pressure and prevention of complications. In patients where the hemorrhage is secondary to an AVM, the lesion can sometimes be managed with endovascular ablation therapy.
Subarachnoid hemorrhage, like ICH is associated with a significantly higher mortality. Approximately 30% of patients die before they reach the hospital. In patients who reach the hospital, clipping or coiling of the aneurysm are excellent treatments to prevent recurrences.
Patients who make incomplete recovery require short-term to long-term rehabilitation that can be offered in specialized units.
Stroke is a major health care problem. While its incidence has decreased in the West due to intense attention to risk factor management, it continues to be a leading cause of disability and death in low to middle income countries. There are effective treatments available for patients who suffer an acute stroke but these can only be offered if the patient presents to a stroke center early following the onset of symptoms. Prevention with appropriate attention to risk factors remains the best option in decreasing recurrences.
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Written for June 2016 by
Ashfaq Shuaib MD FRCPC FAHA FAAN
Professor of Medicine and Neurology
University of Alberta, Canada
Director, Stroke Program
University of Alberta
Director Neuroscience Institute
Hamad General Hospital