Transient Ischaemic Attack

A transient ischaemic attack (TIA), or mini-stroke, is a brief episode of neurological dysfunction caused by a temporary disruption in blood flow to the brain. Unlike a major stroke, a TIA does not result in permanent tissue death. However, it shares many of the same symptoms, such as sudden weakness or numbness on one side of the body, difficulty speaking, and sudden vision changes. Recognition and prompt treatment of TIA are very important as it is a significant risk factor for subsequent major strokes.

Signs and Symptoms

TIAs present with a variety of focal neurological deficits that can mimic other conditions. Common symptoms include one-sided facial droop, motor weakness, and sensory deficits. Visual disturbances like amaurosis fugax (temporary loss of vision) and diplopia (double vision) are also prevalent. Patients may experience balance issues, unsteady gait, dysarthria (difficulty articulating speech), and aphasia (difficulty understanding or expressing speech). Symptoms typically last from a few minutes to one or two hours but can occasionally persist longer.

Causes and Risk Factors

TIA and stroke share common underlying pathologies, such as atrial fibrillation, which can lead to clot formation in the heart that travels to the brain. Atherosclerotic plaques in the carotid arteries can also become dislodged and obstruct cerebral blood flow. Risk factors are divided into modifiable (e.g., hypertension, diabetes, smoking) and non-modifiable (e.g., age over 55, family history). Addressing modifiable risk factors is very important in the management and prevention of TIAs.

Pathogenesis

There are three primary mechanisms of cerebral ischaemia: embolism from another part of the body, in situ thrombotic occlusion, and stenosis of cerebral vessels. The middle cerebral artery is most commonly affected. Patterns of infarcts vary based on the mechanism, such as large subcortical infarcts from in situ thrombosis or small, scattered infarcts from artery-to-artery embolism.

Diagnosis

The diagnosis of TIA involves a detailed history and physical examination, focusing on the neurological assessment. The American Heart Association and American Stroke Association define TIA as a brief episode of neurological dysfunction with a vascular cause, typically lasting less than an hour and without significant infarction on imaging. Laboratory tests, cardiac rhythm monitoring, and imaging studies like MRI or CT scans are essential for ruling out other conditions and identifying the cause.

Treatment

Lifestyle Modification

While lifestyle changes have not been definitively shown to reduce stroke risk post-TIA, they are generally recommended. These include smoking cessation, a healthy diet, regular exercise, and moderating alcohol intake. Managing underlying medical conditions like hypertension, diabetes, and hyperlipidaemia is also important.

Medications

Antiplatelet medications such as aspirin and clopidogrel are commonly used for secondary prevention. Anticoagulants may be prescribed if atrial fibrillation is the underlying cause. Blood pressure and cholesterol control are very important, with targets often set at lower levels to minimise stroke risk.

Surgical Interventions

In cases of significant carotid artery stenosis, surgical options like carotid endarterectomy or carotid artery stenting may be considered. These procedures help to remove or bypass the plaque causing the stenosis, thereby reducing the risk of future strokes.

Carotid endarterectomy involves removing plaque from the carotid artery to improve blood flow.

Prognosis

Without treatment, the risk of a subsequent ischaemic stroke within three months of a TIA is approximately 20%, with the highest risk in the first two days. Effective management and preventive measures can reduce this risk by about 80%.

Epidemiology

The incidence of TIA in the United States is estimated to be between 200,000 to 500,000 cases per year. Risk factors include age over 60, high blood pressure, diabetes, and a history of atrial fibrillation or atherosclerosis. Approximately 15 to 30 percent of strokes are preceded by a TIA.

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Self-assessment MCQs (single best answer)

What is a transient ischaemic attack (TIA) most commonly referred to as?

Which symptom is NOT commonly associated with a TIA?

Which of the following is a modifiable risk factor for TIA?

What imaging study is very important for detecting ischaemic lesions in TIA patients?

Which artery is most commonly affected in cases of cerebral ischaemia leading to TIA?

Which medication is commonly prescribed for secondary prevention of stroke after a TIA?

What is the approximate risk of a subsequent ischaemic stroke within three months of a TIA without treatment?

Which surgical intervention is used to treat significant carotid artery stenosis in TIA patients?

What symptom is described by the term "amaurosis fugax"?

Approximately how many cases of TIA occur each year in the United States?