Uncommon causes of stroke

STROKE is the most common cause of adult disability and the third most common cause of death worldwide.

Stroke, or “brain attack”, can be divided into two types, ischaemic and haemorrhagic. In ischaemic stroke, blood clots block a blood vessel supplying the brain, leading to death of the related brain cells. In haemorrhagic stroke, a blood vessel breaks or ruptures and the bleeding results in a large blood clot which causes brain cells to die due to increased pressure.

A good way to remember the different types of stroke is the fact that ischaemic stroke is essentially a “white stroke” as no blood gets to the area of the brain that is affected. Conversely, a haemorrhagic stroke or intracerebral haemorrhage produces a “red stroke”, which describes blood in the brain substance.

This analogy helps me explain to patients and their families what a stroke is and what is happening in the brain. This article will focus on uncommon ischaemic strokes.

Be aware

While members of the public are well aware of heart attacks with symptoms such as sudden onset of chest pain, breathlessness and sweating, patients suffering from a stroke or “brain attack” may experience sudden numbness or weakness of the face, arm or leg especially on one side of the body, sudden confusion with trouble speaking or understanding and trouble walking due to loss of balance or incoordination.

As most of these episodes are painless, it is one of the reasons why medical evaluation and treatment is often delayed in strokes.

Overall, strokes are the result of symptoms and signs from a number of possible underlying disease processes or “causes”. These factors need to be identified and the mechanisms understood in order to minimise brain damage in the early phase of stroke and to prevent recurrence.

The public should be aware that stroke by itself is not a complete diagnosis without understanding the mechanism. This is important to prevent recurrence and to institute proper therapy. This article is not meant to be exhaustive but rather aims to increase the level of public awareness of strokes and its complexities.

Uncommon and unusual causes

The most common cause of stroke in the adult population is due to atherosclerosis. Atherosclerotic disease causing stroke share many conventional risk factors with coronary heart disease and peripheral vascular disease (affecting the legs).

The risk or predisposing factors include hypertension, diabetes, hyperlipidemia, smoking and atrial fibrillation. The most common cause leading to an ischaemic stroke (white stroke) is from rupture of an atherosclerotic plaque. The resulting blood clot causes an in-situ obstruction or may travel further downstream resulting in obstruction there.

However, many other potential diseases exist and can contribute to a stroke. Less common causes of stroke certainly exist, but while some conditions are well described and understood, others are known to be associated with stroke but knowledge on these diseases remain incomplete. In this area, a great deal of research is ongoing, leading to a better understanding of strokes and paving the way for future treatment.

The potential disease processes also differ between ischaemic or haemorrhagic stroke. Some possible but less common causes of ischaemic stroke include cardiac embolism (where the blood clot forms in the chambers of the heart and travels to the brain), arterial dissection, inflammatory and infectious vascular diseases, trauma, moya-moya syndrome and various blood as well as clotting disorders.

In short, there are multiple causes of stroke and the correct diagnosis, including the likely mechanism, will allow specific treatment and prevention. As in all medical conditions, the age of the patient is another important factor.

Cardiac sources of a stroke are another important category but other causes should not be overlooked. While rhythm as well as structural abnormalities of the heart and recent myocardial infarctions (heart attacks) are important causes of stroke, other less common causes include intracardiac tumour ie cardiac myxoma and infection of the cardiac valves.

Less common causes of stroke include an arterial dissection or a tear which occurs in the blood vessel wall, which leads to bleeding within the arterial wall. The bleeding tracks around or along the length of the vessel wall and may cause a stroke if a blood clot forms in the arterial wall and occludes the blood vessel.

Alternatively, a stroke can occur if the blood clot travels further down the vessel and blocks the blood supply downstream. This can occur spontaneously, as a result of trauma (often from straining, contact sports, neck manipulations) or from inherent vessel weakness.

Blood disorders may result in abnormalities in its various components. Among the many abnormalities that occur, it can become relatively “thicker”, reducing normal blood flow. Some disorders may predispose the blood to clot more easily and consequently, contribute to an ischaemic stroke. These blood disorders include polycythaemia, antiphospholipid syndromes, various thrombophilias and thrombocytosis.

Moya moya syndrome

These disorders may even exist in milder forms and may increase the risk of a stroke in patients with co-existing conventional risk factors.

There are many other causes of stroke and they are often classified in a complicated manner in the medical literature. However, one particular entity deserves further mention. This disease entity is called the moya-moya syndrome. It is an unusual and relatively rare cerebrovascular disorder but occurs more frequently in Asia.

The features include progressive occlusion of large vessels in the brain circulation. Consequently, these blockages produce a fine vascular network at the base of the brain which function as alternative conduits to continue supplying blood for the brain. It produces a characteristic “puff of smoke” appearance on arterial studies of the brain vessels and was first described by Japanese neurologists, hence the name.

This disease can occur in children and in younger adults, presenting as ischaemic stroke or intracerebral haemorrhage. Apart from strokes, intellectual delay can occur in children while in adults, it can lead to dementia; a function of poor blood supply.

Inflammatory or infectious causes of a stroke can cause damage to the lining of the blood vessels, producing vessel wall weakness and fragility. Consequently, a blood clot occurs on the inside of the vessel wall and causes a stroke in a similar way as previously described.

Substance abuse is another possible cause of a stroke, particularly in younger patients. These cases are well described in the medical literature. The mechanism of stroke is likely to be related to a sudden surge in blood pressure and neurotoxic by-products of the various drugs of abuse such as heroin, cocaine, ecstasy and amphetamines, damaging the small blood vessels of the brain.

In conclusion, almost any form of circulatory disorder can lead to a stroke. The possible sources start from the chambers of the heart, the large blood vessels supplying the brain and end in the small vessels of the brain vasculature.

In addition, systemic or generalised disease processes can also contribute to a stroke. This underscores the importance of a complete series of investigations and adequate follow-up of a stroke patient at any age to uncover the mechanisms responsible for the stroke in order to prevent recurrence and to institute appropriate treatment.

- The Star