Definition and Overview
A transient ischemic attack (TIA) is a condition in which neurological deficit symptoms caused by focal ischemia of the brain, spinal cord, or retina appear transiently and resolve completely, with the modern definition restricted to cases without tissue infarction [3]. Previously, TIA was defined by symptom resolution within 24 hours; however, if infarction is identified on MRI diffusion-weighted imaging (DWI), it is classified as cerebral infarction regardless of symptom duration.
TIA is a strong precursor to cerebral infarction. The stroke incidence within 90 days after TIA is approximately 10-15%, with half of this risk concentrated within the first 48 hours [1]. Therefore, TIA is a neurological emergency requiring immediate medical evaluation.
Causes and Mechanisms
Thromboembolic Mechanisms
The most common cause of TIA is transient vascular occlusion by atherosclerotic thrombus. Thrombi or emboli originating from the carotid artery, aorta, or heart temporarily obstruct cerebral vessels, with symptoms resolving when the clot spontaneously dissolves and blood flow is restored.
Major causes include the following.
- Large vessel atherosclerosis: Carotid artery stenosis, intracranial artery stenosis
- Cardiogenic embolism: Atrial fibrillation, post-myocardial infarction thrombus, valvular heart disease
- Small vessel disease: Cerebral small vessel disease due to hypertension and diabetes
- Other: Coagulation disorders, arterial dissection, vasculitis
Hemodynamic Mechanisms
Ischemia may also occur when cerebral blood flow autoregulation is impaired during acute blood pressure drops, orthostatic hypotension, or decreased cardiac output.
Symptoms
TIA symptoms vary according to the territory of ischemia and last for several minutes to tens of minutes before resolving completely.
Anterior Circulation (Carotid System) Symptoms
- Unilateral limb weakness or sensory loss
- Speech disturbance: Slurred speech (dysarthria), inability to speak or comprehend language (aphasia)
- Transient monocular visual loss in one eye (amaurosis fugax)
Posterior Circulation (Vertebrobasilar System) Symptoms
- Diplopia (double vision)
- Bilateral limb weakness
- Balance impairment and gait ataxia
- Severe vertigo
- Dysphagia
Diagnosis
ABCD2 Risk Score
The ABCD2 score is used for rapid assessment of early stroke risk after TIA [2].
- A (Age): Age 60 or older = 1 point
- B (Blood pressure): Systolic 140 or higher or diastolic 90 mmHg or higher = 1 point
- C (Clinical features): Unilateral weakness = 2 points, dysarthria (without weakness) = 1 point
- D (Duration): Symptoms lasting 60 minutes or more = 2 points, 10-59 minutes = 1 point
- D (Diabetes): Diabetes mellitus = 1 point
0-3 points: Low risk, 4-5 points: Moderate risk, 6-7 points: High risk
Imaging Studies
- Brain MRI (including DWI): Essential for confirming presence or absence of infarction; more sensitive than CT
- Carotid ultrasound and MRA/CTA: Evaluation of carotid stenosis and intracranial vasculature
- Cardiac evaluation: ECG, echocardiography (assessment of cardiogenic embolic sources)
- Blood tests: CBC, coagulation studies, fasting glucose, lipid panel
Treatment and Prevention
Emergency Management
Upon TIA occurrence, the patient should immediately visit an emergency department for brain MRI, vascular studies, and cardiac evaluation. According to the EXPRESS study, immediate specialized TIA clinic management reduced the 90-day stroke incidence by approximately 80% [1].
Antithrombotic Therapy
- Antiplatelet agents: Short-term dual antiplatelet therapy with aspirin plus/minus clopidogrel is administered for non-cardioembolic TIA [5].
- Anticoagulants: NOAC or warfarin therapy is initiated when a cardiogenic cause such as atrial fibrillation is identified.
Risk Factor Management
- Hypertension: Maintain target systolic blood pressure below 130 mmHg
- Hyperlipidemia: Statin therapy with a target LDL cholesterol below 70 mg/dL
- Diabetes: Glycemic control (HbA1c < 7%)
- Carotid stenosis: Carotid endarterectomy or stent placement is considered for stenosis of 70% or greater