How can I diagnose a Transient Ischemic Attack (TIA)?

Diagnosing Transient Ischemic Attack (TIA)

TIA diagnosis requires urgent brain imaging (CT or MRI), vascular imaging, and cardiac evaluation to rule out stroke and identify underlying causes, as TIAs carry an 8.8% risk of stroke within 7 days and 11.6% within 90 days. 1, 2

Definition and Risk Assessment

A TIA is defined as a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction 3. The traditional time-based definition set the maximum duration at 24 hours, but the newer tissue-based definition emphasizes the absence of permanent tissue damage on imaging 1.

Risk stratification is essential using the ABCD2 score:

• A: Age ≥60 years (1 point)
• B: Blood pressure ≥140/90 mmHg (1 point)
• C: Clinical features (unilateral weakness = 2 points; speech disturbance without weakness = 1 point)
• D: Duration of symptoms (≥60 minutes = 2 points; 10-59 minutes = 1 point)
• D: Diabetes (1 point)

Risk interpretation:

• High risk (6-7 points): ~8.1% stroke risk at 2 days
• Moderate risk (4-5 points): ~4.1% stroke risk at 2 days
• Low risk (0-3 points): ~1.0% stroke risk at 2 days 2

Essential Diagnostic Workup

Immediate Evaluation (Within 24 Hours)

1. Brain Imaging

   • Non-contrast CT or MRI of the head as soon as possible 2, 4
   • CT rules out hemorrhage and alternative diagnoses
   • MRI with diffusion-weighted imaging is more sensitive for detecting acute ischemia 3

2. Vascular Imaging

   • CTA from aortic arch to vertex (preferred) 1, 2
   • Alternatives: MRA or carotid ultrasound (for extracranial vessels) 1
   • Evaluate for carotid stenosis, intracranial atherosclerosis, and other vascular abnormalities

3. Cardiac Evaluation

   • 12-lead ECG immediately to detect atrial fibrillation and other cardiac conditions 1, 2, 4
   • Consider prolonged cardiac monitoring if no etiology identified 3
   • Echocardiography if cardiac source suspected 3

4. Laboratory Tests

   • Complete blood count with platelet count
   • Coagulation studies (aPTT, INR)
   • Electrolytes and renal function
   • Blood glucose level
   • Additional tests based on suspected etiology 1, 2, 5

Clinical Features to Assess

Carefully evaluate for:

1. Focal neurological symptoms:

   • Unilateral weakness (face, arm, and/or leg)
   • Speech disturbance
   • Hemibody sensory loss
   • Acute monocular visual loss
   • Binocular diplopia
   • Hemivisual loss
   • Dysmetria 1

2. Timing and duration of symptoms:

   • Typically resolve within 1 hour
   • Document precise onset and resolution times 1

3. Risk factors:

   • Hypertension
   • Diabetes
   • Smoking
   • Family history of stroke/TIA
   • Atrial fibrillation
   • Hyperlipidemia 6

Differential Diagnosis

Rule out TIA mimics:

• Migraine aura (especially in elderly)
• Todd's paralysis (post-seizure)
• Space-occupying lesions
• Peripheral nerve disorders
• Anxiety 4, 5

Triage Decision-Making

1. High-risk patients (should be hospitalized):

   • Presentation within 72 hours and ABCD2 score ≥3
   • Symptoms of transient, fluctuating, or persistent unilateral weakness or speech disturbance
   • Symptoms resolved but occurred within past 48 hours 1, 3

2. Moderate-risk patients:

   • Symptoms without motor weakness or speech disturbance occurring between 48 hours and 2 weeks
   • Should be evaluated within 24 hours 1

3. Lower-risk patients:

   • Presentation more than 2 weeks after symptom resolution
   • Atypical sensory symptoms (patchy numbness/tingling)
   • Can be seen within one month 1

Pitfalls to Avoid

• Delay in evaluation: Never dismiss TIA symptoms as benign; they require urgent assessment due to high early stroke risk 3
• Incomplete vascular imaging: Ensure both extracranial and intracranial vessels are evaluated 1
• Missing cardiac sources: Atrial fibrillation may be paroxysmal and require prolonged monitoring 3
• Overlooking mimics: Carefully differentiate TIA from conditions with similar presentations 4, 5
• Inadequate risk stratification: Use ABCD2 score to guide management decisions 2

By following this structured approach to TIA diagnosis, you can identify patients at risk, determine the underlying etiology, and implement appropriate preventive measures to reduce the risk of subsequent stroke.