Diagnosis of Transient Ischemic Attack (TIA)
TIA is diagnosed clinically based on sudden-onset focal neurological deficits that resolve completely (typically within minutes to one hour) without evidence of acute infarction on neuroimaging, combined with urgent diagnostic workup to identify the underlying vascular mechanism. 1
Clinical Diagnostic Criteria
The diagnosis of TIA requires three key elements:
Sudden onset of focal neurological symptoms including unilateral weakness (face, arm, or leg), speech or language disturbance, transient monocular vision loss (amaurosis fugax), or other focal deficits that localize to a specific vascular territory 1, 2
Complete symptom resolution, typically within one hour (though the traditional definition allowed up to 24 hours), with most episodes lasting only minutes 1, 3
No evidence of acute infarction on neuroimaging (the tissue-based definition), though up to one-third of patients with symptoms lasting <24 hours may show infarction on MRI diffusion-weighted imaging 1, 4
Key Clinical Features That Support TIA Diagnosis
Abrupt symptom onset rather than gradual progression—sudden onset strongly favors true TIA over mimics 3, 5
Focal neurological deficit that corresponds to a specific arterial territory (carotid or vertebrobasilar) rather than nonspecific symptoms 3, 5
Presence of vascular risk factors including hypertension, diabetes, hyperlipidemia, atrial fibrillation, or known carotid stenosis 1, 6
Mandatory Urgent Diagnostic Workup
The diagnosis is not complete without urgent evaluation to identify the mechanism and assess stroke risk:
Brain Imaging (Within 24 Hours)
CT or MRI of the brain to exclude hemorrhage, identify acute infarction, and rule out stroke mimics 1, 2, 4
MRI with diffusion-weighted imaging (DWI) is superior to CT and detects silent cerebral infarctions in up to 31% of TIA patients, identifying highest-risk individuals 4
Vascular Imaging (Within 24-48 Hours)
Rapid vascular imaging of cervical carotid arteries is mandatory for patients with carotid territory symptoms who may be candidates for intervention, as there is direct correlation between degree of carotid stenosis and stroke risk 1
CTA or MRA from aortic arch to vertex to evaluate for intracranial atherosclerosis, extracranial vascular disease, and arterial dissection 2, 4
Carotid Doppler ultrasound is useful for initial evaluation, though CTA/MRA provides more comprehensive assessment 4, 7
Cardiac Evaluation
Electrocardiogram without delay to identify atrial fibrillation or other arrhythmias as potential cardioembolic sources 2, 4, 7
Echocardiography as indicated based on clinical suspicion for cardiac source of embolism 4, 7
Laboratory Testing
Basic laboratory workup including CBC, electrolytes, creatinine, glucose, and lipid panel 4
Hypercoagulability workup in young patients without traditional vascular risk factors, including antiphospholipid antibodies, protein C/S, and factor V Leiden 2
Critical Diagnostic Pitfalls to Avoid
Do not discharge based solely on negative CT head—CT is insensitive for acute ischemia and does not exclude TIA; many TIAs show no abnormality on CT 2
Do not assume "too young for stroke"—young patients can have TIA from arterial dissection, hypercoagulable states, cardiac sources, or vasculitis 2
Do not delay vascular imaging beyond 48 hours—carotid territory TIA with significant stenosis has a 90-day ipsilateral stroke risk of 20.1%, and early identification allows for urgent revascularization 1, 2
Recognize that nonspecific symptoms and gradual onset favor mimics rather than true TIA—vertigo alone, isolated dizziness, confusion without focal deficit, or syncope are unlikely to represent TIA 3, 8
Differential Diagnosis Considerations
TIA must be distinguished from mimics that present with transient neurological symptoms:
Migraine with aura commonly presents with transient visual and language disturbances, particularly in young women; presence of headache following neurological symptoms supports migraine, though headache can also occur with TIA 2
Seizures are frequently under-evaluated and represent the most common cause of diagnostic error by excess, particularly in elderly patients 8
Hypoglycemia, syncope, or other metabolic disturbances typically cause global rather than focal symptoms 9, 8
Risk Stratification After Diagnosis
Once TIA is diagnosed, immediate stroke risk must be assessed:
The 90-day stroke risk is 11.6%, with 8.8% occurring within 7 days and the greatest risk in the first 48 hours 1
In the setting of symptomatic carotid disease, the 90-day risk of ipsilateral stroke is 20.1% 1
ABCD² score (age, blood pressure, clinical presentation, diabetes, duration of symptoms) helps stratify immediate risk, with scores ≥4 indicating high risk requiring inpatient management 4, 3