A transient ischaemic attack (TIA) is defined as a rapid onset of focal neurological deficit lasting less than 24 hours, with no apparent cause other than disruption of blood supply to the brain.
The majority of TIAs resolve within one hour and episodes of transient monocular blindness (amaurosis fugax) commonly last less than five minutes.
History and examination
A number of TIA mimics exist, including migraine, focal epilepsy and metabolic disturbances, such as hypoglycaemia, transient global amnesia and multiple sclerosis. Therefore a careful history needs to be taken. The history must focus on four key questions about the presentation:
- Were the neurological symptoms focal rather than non-focal?
- Were the symptoms negative rather than positive?
- Was the onset of the symptoms sudden?
- Were the symptoms maximal at onset rather than progressing over a period?
If the answer to each of the four questions is 'yes', then the symptoms were almost certainly caused by a vascular pathology and if the symptoms have fully resolved then the diagnosis is TIA.
The symptoms are anatomically determined by the insult to the neurological structures that are supplied by the vasculature affected. In the case of transient cerebral ischaemia, the symptoms may be weakness, numbness, incoordination, vertigo and disturbance of speech and/or vision.
Temporary reduction in retinal blood flow causes amaurosis fugax with the symptoms classically described as 'a curtain coming down vertically' into the field of vision of one eye.
Risk factors
Risk factors for TIA include hypertension, diabetes mellitus, dyslipidaemia, cardiac disease, obesity, smoking and recreational drug and alcohol use.
A patient who has suffered a TIA will have no residual neurological deficit but physical examination needs to focus on assessing pulse, particularly for AF, BP and auscultating for any cardiac murmurs or carotid bruits.
Risk stratification
Overall, patients who have had a TIA have a two-day stroke risk of approximately 4 per cent, a seven-day stroke risk of around 5.5 per cent, a 30-day stroke risk of around 7.5 per cent and a 90-day stroke risk of approximately 9 per cent. This risk may be stratified using the ABCD2 scoring system (see box).1
| ABCD scoring system | ||
|---|---|---|
| Age | >60 years | 1 point |
| <60 years | 0 points | |
| Blood pressure | >140/90mm Hg | 1 point |
| <140/90mm Hg | 0 points | |
| Clinical features | Speech impairment without weakness | 1 point |
| Unilateral weakness | 2 points | |
| Duration | 10-59 mins | 1 point |
| >60 mins | 2 points | |
| Diabetes mellitus | Yes | 1 point |
The two-day stroke risk is 1 per cent for ABCD2 score 0-3, 4 per cent for ABCD2 score 4-5 and 8 per cent for ABCD2 score 6-7.
TIAs with an ABCD2 score >4 are classified as high-risk and guidelines advise urgent referral for specialist assessment and investigation within 24 hours. TIAs with an ABCD2 score <4 are classified as low-risk and should have specialist assessment and investigation within one week.
Investigation
Patients who have suffered a TIA require blood tests to check their FBC, glucose and lipid profile. Other investigations include ECG and echocardiography to assess for arrhythmia or structural causes of cardioembolism, and carotid arterial imaging in the case of anterior circulation TIAs.
In patients seen acutely after TIA in whom there is uncertainty about the diagnosis, vascular territory or underlying cause MRI brain scanning is advised.
Often specialist TIA clinics will offer a 'one-stop' service with clinical assessment and investigation being undertaken on the same day and current evidence supports early initiation of secondary preventive strategies to minimise the risk of subsequent stroke.
Treatment
TIA management incorporates optimising vascular risk reduction and lifestyle advice focusing on improvements in diet, weight and physical activity, cessation of smoking and recreational drug use, as well as reduction of alcohol intake to fewer than three units per day for men and fewer than two units per day for women.
In addition, the patient must be advised not to drive for one month. BP should be lowered to <130/80mmHg (or <150/80mmHg if >70 per cent carotid stenosis bilaterally). Serum cholesterol should be lowered to <3.5mmol/l and HbA1c should be <7.5 per cent.
Specific treatments involve providing aspirin 300mg immediately and a combination of aspirin 75mg daily in combination with dipyridamole 200mg modified release twice daily subsequently.
Dose titration of dipyridamole may help to reduce the incidence of headache and clopidogrel monotherapy can be considered as an alternative, particularly in aspirin-intolerant patients.
If the TIA is found to be cardioembolic then the patient should be anticoagulated, in the absence of contraindications. Carotid endarterectomy should be offered within two weeks of symptoms (although ideally within two days) to those patients with TIA who have significant symptomatic carotid stenosis (50-99 per cent according to the North American symptomatic carotid endarterectomy trial criteria or 70-99 per cent according to the European carotid surgery trialists' collaborative group criteria).
- Dr Birns is a consultant in stroke medicine, geriatrics and general medicine at Guy's & St Thomas' NHS Foundation Trust and honorary senior lecturer at King's College London
Reference
1. Clairborne Johnston S, Rothwell PM, Nguyen-Huynh MN et al. Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack. Lancet 2007; 369: 283-92.
