Strokes are a disease where time is of the essence. No matter how early one is identified, there is still potential for devastating outcomes depending on where the brain bleed is situation. However, early intervention leads to better patient prognosis as it allows bleeds to be contained and repaired, preventing further brain damage. This requires rapid patient assessment upon his or her arrival at the hospital and, if possible, immediate transfer to a specialist Stroke Unit for care. The results of the assessment can then guide doctors on their clinical approach.
Fortunately, many epidemiological studies have shown that there are some key “risk factors” that can help predict the likeliness of stroke. The results of these studies have helped researchers and clinicians develop risk assessment tools that can be used on patients, advising them on environmental or lifestyle factors that may reduce their likelihood. Yet, equally as important are the assessments carried out after a stroke has occurred, as we do not yet have any concrete way of dramatically reducing stroke incidence in high-risk patients.
It is often said that prevention is better than a cure. However, for the majority of the world’s non-communicable diseases there is no clear-cut way to stop the disease happening. This is, in large part, because the disease is the product of many environmental influences or the additive effects of genes.
The biggest known risk factor for stroke is age. This could be due to the fact that other risk factors, such as hypertension, also have a higher incidence in the elderly. Additionally, there is some evidence that environmental factors such as head traumas may have an important influence on the likelihood of stroke; these can culminate over a lifetime to increase risk.
It is estimated that over half of strokes can be attributed to high blood pressure. Though this can be controlled through lifestyle changes, for the elderly this can be difficult. Infectious diseases that infect the respiratory tract have also been linked with an increased risk of stroke in people over the age of forty. Respiratory infections such as pneumonia or flu are prevalent amongst the elderly, but the link is important: flu can be prevented by a yearly vaccine. This may only have a small impact, but any reduction in stroke incidence is beneficial.
Patient outcome is strongly dependent on the quick recognition of symptoms and access to medical care. In the UK, a public safety announcements with the “FAST” (Face, Arm, Speech, Test) diagnostic tool has been broadcast to help heighten awareness.
Once suspected victims have been brought to hospital, strokes are usually diagnosed from a combination of brain scans, blood tests and heart monitoring. Brain scans are essential, as they are used to see what part of the brain has been affected, the nature of the stroke (ischaemic, caused by a blocked artery, or haemorrhagic, caused by a blood vessel bursting). They can also be used to gauge the severity of the stroke.
Typically, when assessing a suspected stroke, both computed tomography (CT) and magnetic resonance imaging (MRI) are used. The use of both offers a multimodal insight into the nature of the stroke, tissue viability, and degree of blood profusion. CT scans are usually more common, as it is preferable for patients that are less stable. With this comes a compromise, as CT does not have the same resolution or offer the same clarity as MRI scans, often missing acute cortical or subcortical infractions.
MRIs, though less common, tend to be used on patients that present complex symptoms. In patients recovering from transient ischaemic attack (TIA; caused by a temporary interruption of blood supply to the brain), an MRI with DWI (diffusion-weighted imaging) is recommended. MRI-DWI is seen as the best way to diagnose an acute ischemic stroke, allowing high-resolution imaging of brain tissue and identification of tissues that have been put at-risk because of the bleed.
DWI-MRI uses diffusing molecules to generate contrast for MR-produced images. In the case of an acute ischaemic stroke, the image produced by using DWI-MRI shows greater-than-expected restriction of diffusion for the given brain tissue.
Strokes may also be caused by issues in the arteries leading from the heart to the brain. In order to assess these, carotid ultrasounds and echocardiograms are carried out to check if the blood vessels have been restricted. In both carotid ultrasounds and transthoracic echocardiograms, an ultrasound probe is moved across the body. In transoesophageal echocardiograms (TOE), the patient is sedated and the ultrasound probe is passed down the oesophagus. As this allows the probe to get closer to the heart, it gives better detail on the presence or absence of any blood clots.
Some established therapies for those that have suffered strokes are only effective within the first few hours of the stroke happening.
It is also essential that those who are admitted to hospital with suspected stroke also have their swallowing ability assessed. Dysphagia, or the inability to swallow, is a common side-effect of acute strokes. Obviously, this is debilitating but also dangerous as it leaves the patient vulnerable to choking.
Stroke assessment, both pre- and post-stroke, is an essential means of improving patient outcome. Preventative risk assessments can help patients make lifestyle decisions that may help reduce their risk, like opting for an annual flu vaccine or by encouraging an increase in exercise. However, we do not have a “magic bullet” of stroke prevention, and regrettably patients will continue to have strokes no matter the intervention. In these cases, rapid assessment is essential in improving patient outcome. Scans, namely CT and MRI scans, help determine the nature of the stroke and guide doctors on how to proceed with treatment and surgery.
References and Further Reading:
Early Intervention: https://www.ncbi.nlm.nih.gov/pubmed/14694290
Risk Factors and Stroke: https://www.lshtm.ac.uk/improving-treatment-hypertension-very-elderly