- What is Stroke (Cerebrovascular accident; CVA)?
- Risk Factors
- Clinical Examination
- How is it Diagnosed
What is Stroke (Cerebrovascular accident; CVA)?
Stroke is a disease defined as a sudden neurological deficit (e.g. weakness, loss of sensation or other) due to a vascular cause. The deficit must last for longer than 24 hours and is of sudden onset. There are two main types:
- Ischaemic (85%): can be due to a thrombus (a clot forming in one of the blood vessels supplying the brain); or due to an embolus – a clot which travels from another site (usually the heart) to block off one of the arteries in the brain.
- Haemorrhagic (15%): this is due to rupture of one of the arteries in the brain – usually due to an aneurysm (an outpouching of an artery – causing a point of weakness).
There are several other types – including dissection (splitting) of the wall of one of the blood vessels to the brain, or trauma, and others – but they make up a very small percentage. A TIA (or transient ischaemic attack) has the same symptoms as a stroke, but the neurological deficit lasts for less than 24 hours – i.e. the person recovers completely within that time. It is usually caused by a small embolus which is resorbed.
Stroke is the third most common cause of death in developed countries. It is uncommon before the age of 40 and is more common in males. Stroke affects around 1.2% of Australian patients at sometime in their lives, which corresponds to 217,500 Australians affected. With the growing incidence of obesity in Australia (which contirbutes to stroke through hypertension and atherosclerosis- fatty plaques in blood vessels) the incidence of strokes is expected to sky-rocket by 2050. However, the incidence in younger age groups – eg. 40-60 is dropping with better control of hypertension. Stroke is more common in certain races – eg. Afro-Caribbean.
Men are at greater risk of stroke than women up until the age of 55 years, after which both sexes have similar risks. Stroke is a major cause of morbidity and mortality in the elderly.
Whilst stroke is considered a disease more commonly affecting men, women are actually twice as likely to die from stroke than men. In addition, females have additional risk factors for stroke such as oral contraceptives, that are not present in men.
Stroke is uncommon in children accounting for only a small percentage of stroke cases each year. Stroke in children is often secondary to congenital heart disease (embolic stroke), genetic disorders, abnormalities of intracranial vessels or blood disorders such as Thrombophilia. Half of strokes in children are haemorrhagic and these may be associated with long term disabilities.
The risk factors for ischaemic stroke are similar to the risk factors for coronary artery disease:
Unavoidable risk factors
Age greater than 60 (risk of stroke doubles every decade), male sex, family history of stroke, racial origin.
Avoidable risk factors
Hypertension, Diabetes, Smoking, Excess Alcohol consumption, Obesity, Lack of exercise.
Prolonged use of the Oral Contraceptive Pill.
The risk factors for haemorrhagic stroke are
Hypertension, anticoagulant drugs, bleeding disorders, cerebral aneurysm.
Prior to the onset of the stroke, the patient may have previous symptoms due to a TIA -for example transient episodes of weakness on one side or inability to speak, or more commonly – loss of vision in one eye, which usually develops as a “black veil which gradually goes down” – amaurosis fugax. The onset of the stroke is usually sudden, although it can evolve in a step-wise manner over several hours in thrombotic stroke. The deficit lasts for longer than 24 hours. After its development, the neurological deficit may improve gradually over the next few weeks to months, and sometimes it may completely improve, although most patients are left with a residual deficit – often severe. Haemorrhagic stroke also occurs suddenly, though it is usually accompanied by a severe headache. It is more likely to cause coma than ischaemic stroke, due the increase in pressure in the brain.
Early diagnosis of stroke is extremely important so all patients with symptoms suggesting stroke should be assessed in hospital. Stroke commonly presents with loss of sensory and/or motor function on one side of the body (85% of ischemic stroke patients have hemiparesis), change in vision, gait (walking), or ability to speak or understand or sudden, severe headache. Your doctor will ask specific questions about the onset of symptoms, description of the syptoms and possible risk factors such as hypertension and smoking.
The doctor will carefully examine your head and neck looking for signs of trauma or infection. They will also examine your cardiovascular system and neurological system. Due to possible loss of consciousness, important vital signs will be monitored and an airway established.
How is it Diagnosed
CT is very important in the early stages to distinguish haemorrhagic stroke (blood may be seen on the CT scan) and ischaemic stroke (there may be no signs acutely) because this will guide management.
In addition a host of blood tests will be taken including:
- Full blood count – a high white cell count may indicate inflammation or infection;
- Blood glucose: a low blood glucose (eg in a diabetic) may show similar signs to stroke;
- Cholesterol studies – these are often performed to look for treatable high cholesterol.
Around 25% of people die in the first one month following an ischaemic stroke, and up to 75% after a haemorrhagic stroke. Furthermore, the patients that survive are at a high risk of further strokes – recurrent strokes occur are seen in 10% of survivors in the first year. In addition, patients that have suffered a stroke are also at a very high risk for a myocardial infarction (heart attack) due to concominant coronary artery disease. Patients that have surivived the initial period after a stroke are usually left with significant morbidity. Around 1/3 are independently mobile (move on their own), and 1/3 have a severe disability requiring on-going institutional care, and the rest are in between.There is usually some improvement in function after a stroke, although the patient may be left with a severe deficit. The improvement made in the first month can be used to indicate the likely improvement the patient will make in future. A TIA alone is also an important prognostic factor on its own. After a patient has one TIA – there is a 40% chance of them suffering a stroke in the next 5 years, and a 25% risk of death due to heart disease or stroke.
The treatment of a patient with stroke is divided into immediate and long-term management. Immediate treatment is different for ischaemic and haemorrhagic strokes but general principles of management for both are listed:
- Blood glucose monitoring
- Blood pressure control
- Cardiac monitor- ECG for ischemic changes or atrial fibrillation
- Intravenous fluids
- Oxygen- If hypoxic
- Maintaining normal temperature.
The patient should be admitted into a dedicated stroke unit with multidisciplinary staff for rehabilitation. Aspirin (300mg) should be given. The patient’s swallowing ability should be tested (by a speech therapist) and a naso-gastric tube should be given if required to prevent aspiration. Further management is then centred on rehabilitation (physiotherapists, OT’s and speech therapists are important here) and prevention of complications and further strokes. Prevention of further strokes is important and the patient’s risk factors should be addressed. Long term medical management focuses on reduction of cerebrovascular risk to reduce recurrent stroke. Low dose aspirin (+/-clopidogrel) is typically prescribed to prevent formation of further clots. Other management of stroke includes changing lifestyle factors (increased exercise, healthy diet and smoking cessation), reduced blood pressure, lipid control (with statins) and strict blood glucose control. Thus additional management will depend on individual patient factors and concurrent disease.
Haemorrhagic strokes are managed differently acutely. The patient is not given Aspirin for fear of further bleeding, and if there are signs of increasing ICP (intra-cranial pressure) urgent neurosurgical treatment is sought. Hypertension should be controlled. In addition, dexamethasone is often prescribed to reduce brain swelling, and nimodipine may be used to lower blood pressure acutely. Long term management is as per ischaemic strokes. Patients with TIA or strokes that have narrowing of the carotid arteries may benefit from surgery – carotid endarterectomy. This procedure involves stripping away the inside of the artery to allow for incresed blood flow. It may be complicated by a stroke, however, hence it is reserved for patients with >70% stenosis and symptoms.
|For more information on how international trials are using CT scans to predict and improve stroke outcomes, please see Professor Lesley Cala’s video on Improving Stroke Outcomes.|
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