Transient Ischaemic Attack (TIA)
Summary
A Transient Ischaemic Attack (TIA) is defined clinically as an acute loss of focal brain or monocular function with symptoms lasting less than 24 hours (typically less than 1 hour) due to inadequate blood supply. The modern "Tissue-based Definition" classifies any transient event with evidence of infarction on MRI as a Stroke, regardless of symptom resolution. TIA is a medical emergency: it is the "warning shot" preceding a major stroke. The risk of stroke is highest in the first 48 hours (up to 10%). Urgent assessment, antiplatelet therapy, and carotid intervention can reduce this risk by 80%. [1,2]
Key Facts
- The "24 Hour" Rule: A historical definition. Most true TIAs resolve within 60 minutes. If symptoms last >1 hour, MRI often shows permanent injury (Stroke).
- Amaurosis Fugax: A TIA of the retina. Patients describe a painless black curtain descending over one eye. Indicates ipsilateral Carotid Artery stenosis.
- Mimics: Migraine aura (positive symptoms like flashing lights), Seizure (positive symptoms like jerking), Hypoglycaemia, Syncope (global, not focal).
- Driving: In the UK (DVLA), patients must not drive for 1 month following a TIA.
Clinical Pearls
Negative vs Positive Symptoms: TIA causes Negative symptoms (Loss of power, loss of sensation, loss of vision). Positive symptoms (Flashing lights, tingling, shaking) suggest Migraine or Seizure.
Don't ignore the Leg: Carotid TIAs affect Face/Arm > Leg. If the leg is weak, consider Anterior Cerebral Artery (ACA).
The "Shaking" TIA: Rarely, severe carotid stenosis causes "Limb-Shaking TIA" (involuntary movements precipitated by standing up/hypoperfusion). Often misdiagnosed as focal seizures.
ABCD2 Score: Historically used to triage. NICE [1] now recommends Aspirin 300mg immediately and valid specialist review within 24 hours for ALL suspected TIAs, effectively abandoning the score for triage delay purposes.
Incidence
- Rate: ~50 per 100,000.
- Risk of Stroke:
- 48 hours: 5-10%.
- 90 days: 10-20%.
Risk Factors
- Hypertension, Atrial Fibrillation, Smoking, Diabetes, Hyperlipidaemia.
Mechanism
- Embolism (Most common): Clot (from Carotid plaque or Heart) lodges in cerebral vessel -> Ischaemia -> Clot lyses/fragments -> Perfusion restored before cell death.
- Hypoperfusion: Severe stenosis + drop in BP -> Watershed ischaemia.
- Small Vessel Disease: Lacunar TIA.
Symptoms (Focal Deficits)
Non-TIA Symptoms (The Mimics)
- Neurology: Usually normal by the time they are seen. Look for subtle signs (Pronator drift, unequal reflexes).
- Pulse: Irregular? (Atrial Fibrillation).
- BP: Hypertension.
- Carotids: Bruit? (Note: Bruit correlates poorly with degree of stenosis).
- Heart: Murmurs (Valvular embolic source).
Immediate
- Blood Glucose: Exclude hypoglycaemia.
- ECG: Atrial Fibrillation.
- Blood Pressure.
- FBC, U&E, Cholesterol, ESR (Giant Cell Arteritis in elderly).
Imaging (Urgent)
- Carotid Doppler Ultrasound: Mandatory for anterior circulation TIA. To determine need for surgery.
- MRI Brain (DWI seq): To look for acute ischemia (reclassifies as Stroke).
- CT Brain: Less sensitive. Only useful to rule out haemorrhage/tumour if symptoms persist or anticoagulation planned urgently.
Cardiac Work-up
- Holter Monitor: If ECG normal but embolic suspicion high.
- ECHO: To look for thrombus/vegetations/PFO.
Management Algorithm
SUSPECTED TIA
(Focal, less than 24h)
↓
GIVE ASPIRIN 300mg
(Unless on anticoag)
↓
REFER TIA CLINIC
(Seen within 24h)
↓
CLINIC ASSESSMENT
- MRI Brain
- Carotid Doppler
↓
┌───────────┴───────────┐
CAROTID STENOSIS ATRIAL FIB
(>50% Symptomatic) (Cardioembolic)
↓ ↓
ENDARTERECTOMY DOAC / WARFARIN
(less than 2 weeks) (Start immed
if imaging clear)
1. Acute Management
- Aspirin 300mg stat: Give immediately (unless bleeding disorder or already on anticoagulant).
- Referral: Rapid Access TIA Clinic (to be seen less than 24 hours). Do not admit unless crescendo TIA, AF, or high risk.
2. Secondary Prevention (Long Term)
- Antiplatelet:
- Clopidogrel 75mg OD (First line).
- If Clopidogrel intolerant: Aspirin + Dipyridamole (MR).
- Anticoagulation (if AF):
- DOAC (Apixaban/Rivaroxaban) or Warfarin. (Wait for imaging to exclude bleed).
- Statin: Atorvastatin 80mg ("Fire and forget").
- BP Control: Target less than 130/80.
3. Carotid Intervention
- Indication: Symptomatic stenosis 50-99% (NASCET criteria).
- Procedure: Carotid Endarterectomy (CEA).
- Timing: Ideally within 2 weeks of symptoms (Stroke risk is highest early on).
- Total Occlusion (100%): Surgery is NOT indicated (no flow to restore, risk of embolic shower > benefit).
4. Lifestyle
- Stop smoking. Diet. Exercise.
- Driving:
- UK Group 1 (Car): Stop for 1 month. No need to inform DVLA if resolved.
- UK Group 2 (HGV): Stop for 1 year. Must inform DVLA.
- Stroke: Major complication.
- Silent Ischaemia: Cumulative cognitive decline (Vascular Dementia).
- Recurrence: High without treatment.
- With Treatment: Risk reduces significantly (lowered by 80%).
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| NG128 | NICE (2019/22) | Aspirin 300mg immed. Review less than 24h. Clopidogrel long term. CEA for >50% stenosis. |
| Stroke Guidelines | RCP | Avoid "Dual Antiplatelet" (DAPT) in TIA unless high risk minor stroke - usually Clopidogrel monotherapy is standard for simple TIA. |
Landmark Studies
1. NASCET Trial (1991) / ECST
- Topic: Carotid Endarterectomy.
- Result: Surgery highly beneficial for symptomatic stenosis 70-99%. Moderate benefit for 50-69%. No benefit for less than 50%.
- Impact: Defined the thresholds for surgery.
2. CHANCE / POINT Trials
- Topic: Dual Antiplatelet Therapy (DAPT) in Minor Stroke/High Risk TIA.
- Result: Short term DAPT (21-90 days) reduces recurrent stroke.
- Impact: Some guidelines now suggest short course DAPT (Aspirin + Clopidogrel) for high risk TIA (ABCD2 >4).
What is a TIA?
Often called a "Mini-Stroke." A blood clot temporarily blocked a vessel in your brain, causing stroke symptoms (weakness, speech loss). The difference is the clot dissolved on its own before permanent damage occurred.
Is it serious?
Yes. It is a "Warning Shot." It means you have the conditions (clots/narrowing) to cause a major stroke. Without treatment, 1 in 10 people have a major stroke within days.
What is the treatment?
We start "blood thinning" tablets (Clopidogrel) and cholesterol tablets (Statin) potentially for life. We also scan your neck arteries (Carotids). If they are narrowed, we might operate to clean them out.
Can I drive?
You must not drive for 1 month. You do not need to tell the DVLA unless you have residual problems after that month or drive a lorry/bus.
Primary Sources
- NICE Guideline NG128. Stroke and transient ischaemic attack in over 16s: diagnosis and initial management. 2019.
- Royal College of Physicians. National Clinical Guideline for Stroke. 2016.
- Rothwell PM, et al. Analysis of pooled data from the randomised controlled trials of endarterectomy for symptomatic carotid stenosis (NASCET/ECST). Lancet. 2003;361:107-116.
Common Exam Questions
- Neurology: "Patient with left arm weakness for 30 mins. CT normal. Treatment?"
- Answer: Aspirin 300mg + Urgent TIA Clinic. (Do not wait for MRI).
- Vascular Surgery: "Patient with TIA and 100% Carotid Occlusion. Plan?"
- Answer: Best Medical Therapy (No surgery for 100% occlusion).
- Ophthalmology: "Curtain over vision. Diagnosis?"
- Answer: Amaurosis Fugax (Carotid embolus).
- Driver's License: "HGV driver with TIA?"
- Answer: Stop 1 year. Inform DVLA.
Viva Points
- Crescendo TIA: Definition? Two or more TIAs in a week. Mandates hospital admission.
- DWI MRI: What does it show? Restricted diffusion (bright signal) indicates cytotoxic oedema/cell death. If positive, it's clinically a stroke.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.