A transient ischemic attack (TIA) is a temporary episode of neurological dysfunction caused by insufficient blood flow to a localized part of the brain, spinal cord, or retina, without acute tissue infarction. It produces symptoms resembling those of an ischemic stroke, but the symptoms resolve. Although sometimes called a “mini-stroke,” a TIA is an important marker of subsequent stroke risk rather than a harmless event. (professional.heart.org)
Definition and distinction from stroke
Historically, TIA was defined by symptoms that disappeared within 24 hours. In 2009, the American Heart Association and American Stroke Association adopted a tissue-based definition, distinguishing temporary ischemic dysfunction from an event that causes infarction. Under this approach, an episode with resolved symptoms but an acute ischemic infarct on imaging is classified as ischemic stroke, not TIA. Symptom duration alone therefore cannot establish the distinction. (ahajournals.org)
Magnetic resonance imaging (MRI), especially diffusion-weighted imaging, helps identify acute infarction. Nevertheless, diagnosis remains clinical: symptoms may have disappeared before assessment, the neurological examination may be normal, and no single test confirms every suspected TIA. (ahajournals.org)
Causes and risk factors
A TIA commonly results from a temporary arterial blockage by a blood clot. The clot may form locally or travel from elsewhere, including the heart. Atherosclerosis in arteries supplying the brain can contribute to narrowing and clot formation. Restoration of blood flow allows the neurological symptoms to resolve. (heart.org)
TIA and ischemic stroke share vascular risk factors, including increasing age, hypertension, diabetes mellitus, smoking, abnormal blood lipids, and atrial fibrillation. Their presence supports assessment of vascular disease but does not, by itself, establish the cause of a particular episode. (professional.heart.org)
Clinical features
Symptoms generally begin abruptly and correspond to the function of a particular vascular territory. Common manifestations include:
- Weakness or numbness affecting one side of the face or body.
- Difficulty speaking, understanding language, or articulating words.
- Sudden visual loss, including loss of vision in one eye.
- Double vision, impaired coordination, or difficulty walking, particularly in posterior-circulation events. (professional.heart.org)
Symptoms often last minutes and typically less than an hour, but a brief duration does not establish that an event was a TIA. During the episode, its symptoms can be indistinguishable from those of an evolving stroke. (professional.heart.org)
Diagnosis and investigation
The diagnosis depends on a detailed account of symptom onset, affected functions, duration, and recovery, together with neurological examination and investigation for vascular causes. Important alternative explanations include migraine, seizures associated with epilepsy, and hypoglycemia. The sequence and character of symptoms help distinguish these conditions, although individual features are not definitive. (professional.heart.org)
Investigations address both the episode and its underlying cause. Brain imaging assesses infarction and alternative pathology. Computed tomography can detect hemorrhage and other structural abnormalities but is less sensitive than diffusion-weighted MRI for small acute ischemic lesions. NICE guidance does not use routine brain CT for suspected TIA unless an alternative diagnosis detectable by CT is suspected; it considers MRI after specialist assessment. (nice.org.uk)
Vascular imaging evaluates narrowing or blockage in arteries supplying the brain. Cardiac investigations assess possible embolic sources, and blood glucose testing helps identify hypoglycemia as a mimic. These investigations complement, rather than replace, the clinical history. (professional.heart.org)
Subsequent stroke risk
Stroke risk is particularly elevated soon after a TIA. The American Heart Association’s 2023 scientific statement reported that 90-day risk can be as high as 17.8%, with nearly half of those strokes occurring within two days. This is an upper estimate from studied populations, not a uniform probability for every individual. (ahajournals.org)
Clinical scores such as ABCD2 estimate risk using age, blood pressure, symptoms, duration, and diabetes. However, they do not capture every important mechanism. NICE bases its assessment pathway on specialist evaluation within 24 hours irrespective of clinical risk-score stratification. (professional.heart.org)
Clinical management and secondary prevention
Management focuses on identifying the cause and preventing subsequent ischemic events. Antithrombotic treatment depends on the mechanism: antiplatelet drugs, including aspirin, are used in appropriate non-cardioembolic disease, whereas anticoagulation has an established role when atrial fibrillation is responsible. Short-term dual antiplatelet treatment is reserved for selected circumstances, including certain high-risk TIAs; it is not a routine long-term strategy. (professional.heart.org)
Secondary prevention also addresses blood pressure, blood lipids, diabetes, smoking, diet, and physical activity. In selected patients with symptomatic carotid artery narrowing, carotid endarterectomy—an operation to remove obstructing plaque—is part of prevention. The choice of treatment depends on vascular findings, comorbidities, bleeding risk, and the identified cause of the event. (professional.heart.org)