Transient Ischaemic Attack (TIA)

Introduction

A transient ischaemic attack (TIA) is a sudden onset focal neurologic deficit of vascular origin lasting less than 24 hours.¹

A TIA is an urgent condition, as it may serve as a warning sign for an impending stroke. Without intervention, more than 1 in 12 patients will have a recurrent stroke within one week.²

Aetiology

TIA involves a temporary non-functioning of a focal area of the brain due to disruption of the blood flow.³

This disruption is typically caused by an embolus, a dislodged blood clot that can travel in the bloodstream and block cerebral arteries. The reduced blood flow deprives brain cells of oxygen and nutrients, leading initially to a reversible neurologic deficit. 

If blood flow is restored before permanent brain injury occurs, the TIA resolves. If the flow is not restored, the neurologic deficit will remain as an ischaemic stroke.

Atrial fibrillation and carotid stenosis are the most important causes to identify, as these have a higher rate of early recurrent stroke.  

Risk factors

Risk factors for TIA include:⁴

• Age: TIAs are more common in adults over 55
• Sex: men are at a slightly higher risk than women
• Smoking
• Hypertension
• Atrial fibrillation
• Diabetes
• Family history of stroke or TIA
• Prior TIA or stroke
• Vasculitis

Clinical features

The clinical features of a TIA vary depending on the arterial territory involved.

The most important clinical features to identify are the sudden onset of symptoms and short duration. These two features help differentiate TIA from mimics and other neurological disorders.

The clinical features should appear immediately. The average duration of a TIA is less than 10 minutes. Only 1 in 4 sudden neurological attacks self-resolve as TIA; 3 in 4 will remain as a permanent stroke. 

TIAs can present with a wide range of neurological symptoms, including:⁵

• Weakness: temporary weakness or paralysis, often on one side of the body (hemiparesis)
• Numbness or tingling: brief episodes of numbness or a “pins and needles” sensation, often affecting one side of the body
• Speech problems: slurred speech (dysarthria) or difficulty finding words (aphasia)
• Vision changes: transient vision disturbances, such as loss of vision, double vision (diplopia), or loss of vision in one eye (amaurosis fugax)
• Dizziness or loss of balance: sudden dizziness, loss of balance, or difficulty walking, which may lead to stumbling or coordination problems
• Headache: although less common, some individuals may experience a sudden and severe headache during a TIA

For more information, see the Geeky Medics guide to stroke and TIA history taking.

Differential diagnoses

Possible differential diagnoses in the context of suspected TIA include:²

• Hypoglycaemia
• Migraine aura: differences include evolving sequential symptoms > 5 minutes; or spreading out of the topography of visual change or numbness > 5 minutes (as opposed to sudden, completed at onset in TIA)
• Seizure (much more likely to include loss of awareness)
• Syncope

The clinical features, rather than investigations, are most useful in identifying TIA and distinguishing it from these differential diagnoses. 

Investigations

The most important investigations in TIA are an ECG (to identify atrial fibrillation) and carotid artery imaging (for symptomatic carotid stenosis), as these conditions carry higher recurrent stroke risk and alter management.

Bedside investigations

Relevant bedside investigations include:⁶

• 12-lead ECG: to determine if symptoms are linked to a cardiac source (e.g. atrial fibrillation). 

Laboratory investigations

Relevant laboratory investigations include:⁶

• Full blood count: as a baseline
• Blood glucose levels: to identify diabetes
• Lipid profile
• Coagulation screen
• ESR: to exclude giant cell arteritis in ocular TIA or patients with a headache

Imaging

Relevant imaging investigations include:⁶

• CT brain: to rule out bleeding, tumours, or other structural abnormalities
• MRI brain: to identify acute ischemic changes; the absence of acute ischaemic changes despite an attack lasting more than 3 hours can also be helpful to suggest a non-vascular cause such as migraine aura
• CT angiography and MR angiography: to visualise blood vessels in the brain and neck to identify any blockages or abnormalities
• Carotid ultrasound: to assess blood flow in the carotid arteries and detect the presence of plaque or stenosis
• Echocardiography: to investigate for cardiac source of emboli

Management

Unresolved acute neurological deficits present <24 hours should be treated as acute stroke and referred urgently for acute stroke service assessment.

According to the 2023 British and Irish Association of Stroke Physicians Guidelines, the acute management for fully resolved TIAs involves:

• 300mg aspirin immediately
• Referral for assessment within 24 hours by a stroke specialist clinician
• Screen for atrial fibrillation and carotid stenosis*
• If TIA is confirmed and not at high risk for haemorrhage, dual antiplatelets for 21 days: i.e., continue aspirin at 75mg daily and load additionally with clopidogrel 300mg stat, then 75mg daily
• Initiate secondary prevention: lifestyle advice, statin, smoking cessation, hypertension and diabetes management

*These underlying aetiologies alter the acute management of TIA:

• Atrial fibrillation: commence direct oral anticoagulant after assessment by stroke specialist
• Symptomatic carotid stenosis: consider carotid endarterectomy

Complications

The main complication of a TIA is the increased risk of subsequent strokes with long-term disability and cognitive impairment.¹

As discussed, the recurrence rate is significantly increased if the underlying aetiology is atrial fibrillation or carotid stenosis:

• Atrial fibrillation: the 1-year risk may be as high as 10%
• >70% carotid stenosis: the 1-year risk may be as high as 16%

Many of these recurrences will occur within the first 14 days. 

The annual recurrence risk for non-AF non-carotid TIA is below 2%.

Key points

• A transient ischaemic attack (TIA) is a sudden, temporary neurologic deficit of vascular origin lasting less than 24 hours
• The symptoms are specific to the affected arterial territory, often involving hemiparesis or aphasia
• The most important causes of TIA are atrial fibrillation and carotid stenosis
• Key investigations include ECG, CT/MRI brain and carotid ultrasound
• Medical management of resolved TIA involves 300mg aspirin and then urgent stroke clinician assessment
• 21 days of dual antiplatelet therapy reduces recurrent stroke risk in non-carotid, non-atrial fibrillation stroke
• If identified, atrial fibrillation may require anticoagulation (DOAC), and carotid stenosis may require carotid endarterectomy
• The primary complication of TIA is an early risk of subsequent strokes

Reviewer

Professor Simon Cronin

Consultant Neurologist

Cork University Hospital and School of Medicine, University College Cork

Editor

Dr Chris Jefferies

References

1. National Institute of Neurological Disorders and Stroke. Transient Ischemic Attack (TIA). Published in 2023. Available from: [LINK]
2. Wilkinson, et al. Oxford Handbook of Clinical Medicine. Published in 2017. Oxford University Press
3. Panuganti KK, Tadi P, Lui F. Transient ischemic attack. In: StatPearls [Internet]. Published in 2023. Available from: [LINK]
4. Khare S. Risk factors of transient ischemic attack: An overview. Published in 2016. Available from: [LINK]
5. Lewandowski CA, Rao CPV, Silver B. Transient ischemic attack: definitions and clinical presentations. Published in 2008. Available from: [LINK]
6. Coutts SB. Diagnosis and management of transient ischemic attack. Published in 2017. Available from: [LINK]
7. NICE. Stroke and transient ischaemic attack in over 16s: diagnosis and initial management. Published in 2019. Available from: [LINK]