What are the diagnostic criteria and steps for diagnosing a Transient Ischemic Attack (TIA)?

Diagnostic Approach to Transient Ischemic Attack (TIA)

TIA is a clinical diagnosis requiring immediate risk stratification and comprehensive diagnostic workup within 24 hours for high-risk patients, with brain imaging, vascular imaging, and ECG as mandatory components. 1

Clinical Diagnosis and Initial Assessment

TIA remains fundamentally a clinical diagnosis based on sudden-onset focal neurological symptoms that resolve, typically within minutes to hours. 2 However, diagnostic accuracy among emergency medical staff is approximately 90%, with 20-30% of cases incorrectly labeled, necessitating close collaboration between emergency department staff and stroke specialists. 2

Key Diagnostic Features to Identify:

• High-risk symptoms requiring immediate evaluation within 24 hours: unilateral motor weakness, facial weakness, or language/speech disturbance presenting within 48 hours 1
• Moderate-risk symptoms requiring evaluation within 2 weeks: hemibody sensory changes, monocular vision loss, binocular diplopia, dysarthria, dysphagia, or ataxia without motor/speech involvement 1
• Patients with residual symptoms at presentation should be considered as potentially having a stroke and evaluated for thrombolysis eligibility 3

Mandatory Diagnostic Workup

Brain Imaging (First Priority)

• MRI with diffusion-weighted imaging is preferred over CT for superior sensitivity in detecting ischemic changes, though CT is acceptable if MRI is unavailable 1, 4
• Brain imaging is essential to differentiate cerebral ischemia from intracerebral hemorrhage and exclude stroke mimics (space-occupying lesions, arteriovenous malformations, seizure-related Todd's paralysis) 2, 5
• Timing: Immediate for high-risk patients, within 48-72 hours for low-risk patients 2

Vascular Imaging (Second Priority)

• CT angiography from aortic arch to vertex should be performed immediately, ideally at the time of initial brain CT, to assess both extracranial and intracranial circulation 1
• For anterior circulation symptoms specifically: noninvasive carotid imaging (carotid duplex ultrasonography) within 48 hours is mandatory to identify surgically remediable carotid stenosis 1, 4, 5
• Alternative acceptable modalities: carotid ultrasound with transcranial Doppler or MR angiography based on availability 1
• For posterior circulation TIAs: MRA or conventional arteriogram to guide antiplatelet or anticoagulation therapy 5

Cardiac Evaluation (Third Priority)

• 12-lead ECG must be completed immediately upon arrival to identify atrial fibrillation or other cardioembolic sources 1, 4
• ECG is a necessary component of initial assessment for all TIA patients 4
• For non-hospitalized patients, cardiac evaluation including ECG should be performed within 24-48 hours 4

Routine Laboratory Investigations

• Full blood count, electrolytes, renal function, cholesterol, and glucose levels should be obtained, though direct evidence for each individual test is lacking 2, 5
• These investigations help identify hematological abnormalities and vascular risk factors 5

Risk Stratification Using ABCD2 Score

The ABCD2 score helps stratify early stroke risk but should supplement, not replace, comprehensive evaluation: 6

• Age ≥60 years: 1 point
• Blood pressure ≥140/90 mmHg: 1 point
• Clinical features: unilateral weakness (2 points), speech disturbance without weakness (1 point)
• Duration: ≥60 minutes (2 points), 10-59 minutes (1 point)
• Diabetes: 1 point

High-risk patients (ABCD2 ≥4) face 8% stroke risk at 2 days versus 1% in low-risk patients (ABCD2 <4). 6 However, the ABCD2 score alone should not determine disposition decisions. 1

Additional High-Risk Indicators Beyond ABCD2

• Acute ischemic lesions on diffusion-weighted imaging 7
• Carotid stenosis >50% (absolute contraindication to outpatient management) 1, 7
• Severe intracranial artery stenosis 7
• Microembolic signals on transcranial Doppler 7
• Atrial fibrillation 7
• Hypercoagulable states 1
• Crescendo TIAs (never discharge under any circumstances) 1

Timing and Disposition Algorithm

High-Risk Patients (ABCD2 ≥4 or any high-risk indicator):

• Immediate hospitalization to stroke unit with complete diagnostic workup within 24 hours 2, 1, 6
• Early stroke risk is as high as 10% within the first week, making this a true medical emergency 1

Low-Risk Patients (ABCD2 <4):

• May be managed in community with CT brain and carotid ultrasound within 48-72 hours 2
• Can be referred to specialist TIA clinic and seen within 7-10 days 2

Critical Pitfalls to Avoid

• Never discharge patients with crescendo TIAs under any circumstances 1
• Do not delay carotid imaging in anterior circulation TIAs, as urgent revascularization may be needed—the benefit of carotid endarterectomy is greatly diminished beyond 2 weeks after symptom onset 1
• Never rely solely on ABCD2 scores for disposition decisions—they supplement but do not replace comprehensive evaluation 1
• Delaying imaging beyond 48 hours increases recurrent stroke risk (8.8% at 7 days, 11.6% at 90 days) 4
• Failing to perform carotid imaging in carotid territory TIA, where 90-day ipsilateral stroke risk can reach 20.1% 4
• Never discharge without confirming outpatient follow-up arrangements 1
• Do not discharge patients within 24 hours if complete diagnostic workup shows embolic source requiring immediate treatment, acute infarction on brain imaging, or significant carotid stenosis 1

Safe Discharge Criteria (After 24 Hours Only)

Patients can be safely discharged only if: 1

• Complete diagnostic workup shows no embolic source requiring immediate treatment
• No acute infarction on brain imaging
• No significant carotid stenosis