Transient Ischaemic Attack

A transient ischaemic attack is a brief episode of focal neurological or retinal dysfunction caused by temporary ischaemia, with full recovery and no acute infarct on diffusion weighted MRI. Most episodes resolve within 1 hour, and it is a medical emergency because it predicts early stroke.

Incidence rises steeply with age and is similar in men and women until the seventh decade. Older cohorts reported about 10% stroke risk at 90 days with half of events in the first 2 days; with rapid assessment and treatment, contemporary 90 day risk is about 2 to 5%.

Causes. Large artery atherosclerosis (carotid, vertebral, intracranial), cardioembolism (atrial fibrillation, recent myocardial infarction, valve disease), small vessel disease, arterial dissection, and less often vasculitis, hyperviscosity and paradoxical embolism.

Risk stratification. The ABCD2 score gives 1 point for age 60 or over, 1 for blood pressure 140/90 mmHg or over, 2 for unilateral weakness or 1 for speech disturbance without weakness, 2 for duration of 60 minutes or more or 1 for 10 to 59 minutes, and 1 for diabetes. A score of 4 or more is high risk, but a low score does not exclude carotid stenosis or atrial fibrillation, so every patient needs full assessment.

Pathophysiology.

A transient embolus or haemodynamic reduction in flow causes reversible neuronal dysfunction. Rapid lysis of the embolus or collateral recruitment restores flow before infarction.

Unstable plaque, with ulceration and thrombus, drives recurrent embolism and explains the clustering of strokes in the first days.

• Sudden onset of unilateral weakness, facial droop, sensory loss, dysphasia or dysarthria, lasting minutes.
• Monocular visual loss (amaurosis fugax), described as a curtain, from retinal ischaemia.
• Vertigo with diplopia, dysarthria, ataxia or crossed sensory loss suggests a posterior circulation event; isolated brief vertigo is rarely a TIA.
• Limb shaking on standing suggests critical carotid occlusion.
• Examination is often normal at assessment; check pulse rhythm, blood pressure in both arms, carotid bruits and fundi.

Red flags.

• Two or more events within 7 days, or increasing frequency (crescendo).
• Event while taking an anticoagulant, or known atrial fibrillation.
• Residual deficit, a new neurological sign, or severe headache.
• Known carotid stenosis of 50% or more, or ABCD2 score of 4 or more.

• Specialist assessment within 24 hours of symptom onset for every suspected TIA; emergency assessment for crescendo events.
• Brain imaging: MRI with diffusion weighted sequences is preferred; non-contrast CT excludes haemorrhage when MRI is unavailable.
• Vascular imaging of the head and neck by CT angiography, MR angiography or carotid duplex ultrasound, done at the same visit when possible.
• 12 lead ECG for all, then ambulatory monitoring for at least 24 hours, extended to 14 to 30 days in cryptogenic cases; echocardiography when a cardiac source is suspected.
• Blood tests: glucose, HbA1c, lipids, full blood count, creatinine and eGFR, ESR or CRP; further tests in young adults (thrombophilia, autoimmune screen, vasculitis, syphilis serology).

Differential diagnosis. Migraine aura, focal seizure with Todd paresis, hypoglycaemia, syncope, peripheral vestibular disease, transient global amnesia, multiple sclerosis, subdural haematoma, brain tumour, functional neurological disorder, and retinal causes of visual loss.

• Same day antithrombotic treatment once haemorrhage is excluded.
• Aspirin 300 mg orally once as a loading dose (300 mg rectally if swallowing is impaired), then 75 mg orally once daily with food. Maximum 300 mg daily. Continue with clopidogrel for 21 days for high risk events, then use a single agent long term. Monitor for bleeding and dyspepsia, and check full blood count. Avoid in active peptic ulcer, bleeding disorders, aspirin sensitive asthma and in children under 16 years; use caution when eGFR is under 10; low dose use is acceptable in pregnancy when needed.
• High risk TIA (ABCD2 score of 4 or more) or minor stroke without a cardioembolic source: clopidogrel 300 mg orally once as a loading dose, then 75 mg orally once daily, with aspirin for the first 21 days, then clopidogrel alone long term. Maximum 75 mg daily after loading. Monitor bleeding and full blood count. Avoid in active bleeding; use caution in severe hepatic impairment; reduced effect in CYP2C19 poor metabolisers; avoid omeprazole and esomeprazole; avoid in pregnancy unless clearly needed.
• Atorvastatin 80 mg orally once daily, long term. Maximum 80 mg daily. Monitor lipids at 4 to 12 weeks and ALT at baseline and if symptoms occur; check creatine kinase for myalgia. No dose change in renal impairment; avoid in active liver disease; limit to 20 mg daily with clarithromycin and avoid with ciclosporin; contraindicated in pregnancy and breastfeeding. Aim for LDL cholesterol under 1.8 mmol/L.
• Blood pressure: start or intensify treatment after the first 24 to 48 hours, aiming for under 130/80 mmHg with an ACE inhibitor, a thiazide like diuretic or a calcium channel blocker as tolerated.
• Atrial fibrillation: oral anticoagulation, started immediately after a TIA once haemorrhage is excluded, instead of antiplatelet therapy.
• Symptomatic carotid stenosis of 70 to 99%, and selected cases of 50 to 69%: carotid endarterectomy as soon as possible, ideally within 7 days and no later than 14 days.
• Lifestyle: stop smoking, reduce alcohol, Mediterranean style diet, regular exercise, weight control, and treat diabetes with a target HbA1c of about 53 mmol/mol (7%).

Monitoring. Review at 1 week for blood pressure and adherence, at 3 months for lipids, and yearly thereafter.

Referral and escalation. Emergency referral if symptoms recur, persist or fluctuate; vascular surgery for symptomatic stenosis; cardiology for atrial fibrillation or structural source; inform patients about driving restrictions, which vary by jurisdiction.

Special groups. Young adults: investigate for dissection, patent foramen ovale, thrombophilia, vasculitis and drug use. Pregnancy: low dose aspirin is acceptable; avoid statins and clopidogrel unless clearly needed.