Patients who still have symptoms when they present to you should be sent into hospital immediately using the stroke pathway, even if less than 24 hours have elapsed since the symptoms began
TIA definition
TIA is a clinical syndrome presenting as acute loss of focal cerebral or monocular function, due to inadequate cerebral or ocular blood supply, and lasting less than 24 hours. Although TIA is often referred to as a ‘mini-stroke’ (i.e. transient ischaemia in the brain), the definition here also includes an attack of ischaemia in the eye, because these also indicate a risk of impending stroke and they are therefore managed in a very similar way.
Clinical Features
Accurate diagnosis of TIA usually depends entirely on the history. In most cases the symptoms and signs have already gone by the time the patient seeks medical help.
| TIA unlikely | TIA likely | |
|---|---|---|
| Types of symptom |
Unilateral weakness or clumsiness Slurring of speech in clear consciousness(particularly if accompanied by a facial droop) Sudden loss of language(dysphasia)in clear consciousness |
Simultaneous bilateral weakness Confusion (but beware: jumbled speech could represent a TIA with dysphasia) Loss of memory Isolated vertigo (illusory sense of spinning or other motion) Faintness |
| Charateristics of these symptoms |
Abrupt focal loss of neurological function Complete recovery within 24 hours Known vascular risk factors |
Gradual onset Evolution of symptoms (e.g. spread from one body part to another or gradual change in the character of the symptoms) Prominent positive features (pain, stiffness, very prominent tingling or other dysaesthesia) |
More detailed information on the diagnosis of TIA can be found on the RCP website www.rcplondon.ac.uk or to download the 2008 National clinical guideline for diagnosis and initial management of acute stroke and transient attack (TIA).
Symptom duration
Typically the symptoms of a TIA will last for between two minutes and thirty minutes, but this is not an entirely reliable way of discriminating cerebrovascular disease from other pathologies.
Attacks lasting for less than two minutes:
Purely sensory symptoms lasting less than two minutes are unlikely to turn out to be TIAs, so other possibilities should at least be considered first. Better imaging modalities are now demonstrating that patients with extremely brief episodes of weakness or clumsiness, of just 30 seconds or so, can turn out to have very small infarcts. Furthermore symptoms of retinal ischaemia may be very short-lived, possibly lasting just a few seconds.
Attacks lasting for more than thirty minutes:
If a patient still has symptoms when they first present themselves to a doctor, and cerebrovascular disease seems a plausible explanation, then it should be assumed that they have had a stroke rather than a TIA, even if 24 hours has not yet elapsed. They should be sent into a hyperacute stroke unit immediately. Attacks that have already lasted for more than an hour are unlikely to recover completely within 24 hours, so this is already a fair assumption. If the correct diagnosis turns out to be a TIA, i.e. the symptoms and signs have all recovered completely within the first 24 hours, it is still likely that this is a high-risk TIA in which case your patient needs assessment and treatment immediately anyway.
Differential diagnosis of TIA
TIA is not an entirely straightforward diagnosis; there are a number of other neurological conditions which can mimic TIA.
Focal neurological disturbances which evolve:
There are two neurological conditions which cause an evolution of symptoms, e.g. spread of symptoms from one body part to another, or a gradual change from one symptom (e.g. tingling) to another (e.g. twitching). These are seizures and migraine. Such evolution would be extremely unusual for a TIA.
Seizures are most typically characterised by positive neurological disturbances such as involuntary twitching, stiffness, or even just very prominent tingling. They may lead to an alteration in the level of consciousness which is extremely unusual for a TIA. There will often be a history of epilepsy, even if it has been quiescent for years, and a positive family for epilepsy could be another useful clue. Epilepsy can occur at any age, whereas TIAs are relatively rare in young patients with no known risk factors.
Migraines can lead to focal neurological disturbances, usually but not always associated with a headache. As with seizures, symptoms will typically evolve. Focal neurological sensory disturbances associated with a unilateral throbbing headache, nausea and photophobia are very likely to be fully explained by migraine. Migraines can also cause some clumsiness but they do not generally cause weakness (other than in familial hemiplegic migraine which is a rare condition). Thus if a patient with known migraine has a new attack with sudden-onset unilateral weakness in the context of a migraine headache, one possibility is that the ischaemia of a TIA has triggered off the migraine, so in this case the patient should be referred urgently.
Transient global amnesia:
Isolated amnesia is probably not caused by TIA. A patient who has in clear consciousness temporarily lost the ability to lay down new memories for an hour or two is likely to have suffered an attack of transient global amnesia. Typically such an attack can be brought on by a change in temperature (e.g. on emerging from a hot shower), by vigorous exercise or by psychological stress. The important feature of this diagnosis is that it constitutes a failure only of storing ‘episodic’ memory (i.e. laying down memories of autobiographical events), with ‘semantic’ memory (factual information about the world) intact. If there is a broader cognitive disturbance then other diagnoses (such as epilepsy) have to be considered. Typically a fully alert individual asks the same questions about where they are or what they are supposed to be doing over and over again, without appearing to register the answers given. Afterwards they will remember nothing about the attack, just that there is a segment of time missing from their memory.
Syncope and presyncope:
TIAs do not tend to cause a feeling of faintness or any alteration in the patient’s level of consciousness. TIA is not a cause of transient loss of consciousness, so this clinical scenario should prompt the search for an alternative diagnosis such as vasovagal syncope, cardiac syncope or epilepsy.
If in doubt, discuss or refer:
Missing a TIA is potentially dangerous error, particularly if the patient goes on to have a stroke which could have been prevented. When in doubt it is always better to contact the relevant stroke service (contact details given on the referral form) and discuss the case rather betting on an alternative diagnosis and losing.