INTRODUCTION - TIA V1 with changes

THE TIA SERVICE AT KINGS COLLEGE HOSPITAL.
WHAT IS A TIA?
The classic definition of a Transient Ischaemic Attack (TIA) is a sudden, focal
neurological deficit that lasts for less than 24 hours, presumed to be of vascular origin.
It is caused by temporary disturbance of blood supply to an area of the brain, which
results in sudden, brief impairment of brain function and consequent transient
neurological dysfunction. It was traditionally assumed that resolution of symptoms
implied that no neurologic damage had occurred, but modern imaging techniques
reveal signs of fresh acute infarction in 30 – 50% of such patients. Thus it was felt
that a tissue based definition is more appropriate and the American Heart Association
endorsed a new definition of TIA as ‘a brief episode of neurologic dysfunction caused
by focal brain, spinal cord or retinal ischaemia, without evidence of infarction’1
TIAs are usually warning signs that a person is at risk of an impending more serious
and debilitating stroke. Early recognition of a TIA offers a short window of
opportunity to intervene to help prevent a disabling ischaemic stroke. It is therefore
essential that patients with suspected TIA are seen in a comprehensive rapid access
TIA Service which provides specialist assessment, investigation, treatment and
intervention on an urgent basis
PREDICTION OF STROKE RISK
For several years the incidence of stroke after a TIA was underestimated. More recent
studies have shown that TIAs are not benign and are associated with a significant
early risk of stroke. In a population based study, the risk of stroke after a first TIA
was 8.6% at 7 days and 12% at 30 days2
. In an Emergency Department (ED) based
study in Northern California, the 90 day risk of stroke after a TIA was 10.5% but half
of these strokes occurred very early within the first 2 days of the TIA3
. Even more
recently it has been shown that 42% of the strokes which occur in the 30 days after a
TIA actually occur within the first 24 hours4
highlighting the need to treat TIAs as an
acute medical emergency.
The ABCD2
Score has been shown to be predictive of the risk of stroke at 2 days after
a TIA and it is very useful to triage patients who should be treated as an acute medical
emergency and sent to A&E from those who require urgent referral to the TIA
Service. A score is assigned according to the patient’s Age, Blood pressure, Clinical
features, Duration of symptoms and Diabetes (Table 1)
For patients with an ABCD2
score of 0-3, the 2 day risk of stroke after a TIA was 1%,
for those with a score of 4-5, the 2 day risk was 4.1% and for those with a score of 6-7
the risk was 8.1%5
. Thus patients with a score of 0-3 are deemed to be at low risk
while patients who score 4 or above are deemed to be at intermediate to high risk of
an early stroke within 48 hours of symptom onset and should be sent straight to
casualty for emergency admission and investigation.
There are certain circumstances, however, where the ABCD2
Score does not quite
reflect the patient’s true risk. The National Clinical Guideline for Stroke6
state very
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clearly that people with crescendo TIAs (two or more TIAs in a week) should be
treated as being at high risk of stroke and treated as an emergency even though they
may have an ABCD2
score of 3 or below. Also patients in Atrial fibrillation, those on
anticoagulation or those with symptoms of TIA and significant head and neck pain
suggestive of a dissection are clearly at high risk whatever the ABCD2
Score and
should also be treated as medical emergencies and sent immediately to A&E.
DIFFERENTIAL DIAGNOSIS
Since TIAs represent focal interruption of blood supply to a localised area of the
brain, they usually present with focal symptoms. Thus symptoms of global
neurological dysfunction such as light-headedness, faintness, generalised weakness or
lethargy or loss of consciousness are not usually suggestive of TIAs, in the absence of
any accompanying focal features.
TIAs are not the only causes of transient focal neurological dysfunction and it is
important to distinguish true ischaemic TIAs from non-ischaemic events or ‘TIA
mimics’ (Table 2). Accurate diagnosis of a TIA may be very difficult since it is
entirely dependent on the correct interpretation of the history of a transient event as
remembered and described by the patient. Usually, by the time the patient is seen, the
symptoms have resolved completely, there is little to find on examination and
imaging is frequently normal.
Common TIA Mimics
Migraine Partial seizure
Ocular disorders Hypoglycaemia
Vestibular disorders Brain tumour
Subdural haematoma Arteritis
Hyperventilation Primary cerebral amyloid
Table 2
Migraine with aura is a very common TIA mimic. The focal symptoms tend to spread
gradually from one part of the body to another and may be followed by headache. It
may be particularly difficult to distinguish from TIAs in the older age group where the
2
ABCD2
Score
Pt’s Score
Age >60 y 1
BP >140/90 mm Hg 1
Clinical features Unilateral weakness 2
Speech impairment without weakness 1
Other 0
Duration of symptoms >60 mins 2
10-59 mins 1
<10 mins 0
Diabetes Yes 1
TOTAL
Table 1

focal features of the aura frequently occur without subsequent headache even in
patients with no prior history of migraine with aura.
Recurrent and stereotyped events raise the suspicion of a partial seizure mimicking a
TIA. There may be spread to contiguous parts of the body or amnesia to the event
which support the possibility of seizure. There is a huge list of potential TIA mimics
and an important part of the TIA assessment and investigation is to distinguish an
ischaemic from non-ischaemic aetiology and to establish a diagnosis.
CASE STUDY:
A 64 year man presented to his GP following a 30 minute episode of speech
disturbance and right-sided weakness; by the time he reached the GP’s surgery, he
had returned to normal and no neurological deficits were noted. His blood pressure
was elevated at 170/95 mmHg and he was known to be diabetic. He therefore had an
ABCD2
score of 6 and was deemed to be at high risk. The GP gave the patient a stat
dose of Aspirin 300mg and treated this as an emergency, sending the patient by
ambulance to the emergency department at King’s College Hospital. He was seen in
A&E by the TIA team who felt that this represented a TIA in the distribution of the
Left middle cerebral artery. MRI of the brain, carotid dopplers and ECG were
performed that same day, according to the TIA Protocol. The convential sequences of
the MRI appeared normal, but the Diffusion Weighted Image MRI showed a minute
area of infarction (Figure 1).
Figure 1
ECG showed him to be in AF (not been previously diagnosed) and carotid dopplers
did not reveal any internal carotid artery stenosis.
This TIA was clearly cardioembolic in origin. The treatment options were discussed
with the patient and it was explained that in his case the evidence in the literature
strongly favoured anticoagulation with warfarin for secondary stroke prevention. He
was therefore started immediately on full anticoagulant doses of Enoxaparin and was
given an appointment to return to the anticoagulant clinic on the following day for
3
Very small
area of
infarction in
L MCA
territory

initiation of warfarin. He was to continue on warfarin indefinitely aiming for an INR
of 2-3 and was to continue on cover with Enoxaparin till the INR was within the
therapeutic range.
THE TIA SERVICE AT KINGS
The TIA service at Kings College Hospital is a fast-track service in which all patients
with suspected TIA are seen, investigated and treated within 24 hours of referral, 7
days a week. All suspected High Risk TIA patients are immediately admitted for
observation and work-up. Treatment with antiplatelets is initiated immediately, but
they are kept under hourly neuro observation while in hospital as they would be
potential candidates for thrombolysis if they developed signs of a fresh stroke.
Low Risk patients are seen within 24 hours of receipt of the referral. They are asked
to attend KCH on the following day and after undergoing MRI of the brain, carotid
dopplers, ECG and other relevant investigations they are seen by the specialist team.
The history and results are reviewed and the appropriate treatment initiated. If high
grade carotid stenosis is identified, the patient is seen by the vascular surgeons on the
same day and booked for early carotid endaterectomy, usually within 48 hours.
HOW TO REFER TO THE TIA SERVICE.
High risk patients i.e.
ABCD2 score of 4 or more
Recurrent TIAs
TIAs in AF or on Warfarin
TIAs with prominent head and neck pain suggesting dissection
should be sent to the Emergency Department (A&E) 24 hours a day, 7 days a week,
for same day investigation and admission. If in doubt, the patient may be discussed
with the TIA Nurse specialist or the SpR on call for Stroke (see contact details below)
Low risk suspected TIAs with a score of 0-3 should be referred immediately to the
TIA service: Monday to Friday by contacting the TIA Nurse specialist on
07528977503 or the SpR on call for stroke via KCH switchboard 020 3299 9000, or
by Fax No: 020 3299 8504. On weekends or out of hours, please contact the SpR on
call for stroke via switchboard as the TIA nurse is not available and the Fax is not
manned.
REFERENCES:
1. Easton JD, Saver JL, Albers GW, et al. Definition and evaluation of transient
ischemic attack: A scientific statement for healthcare professionals from the
American Heart Association/American Stroke Association Stroke Council; Council
on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology
and Intervention; Council on Cardiovascular Nursing; and the Interdisciplinary
Council on Peripheral Vascular Disease. Stroke 2009; 40:2276-93.
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2. Lovett JK, Dennis MS, Sandercock PAG, Bamford J, Warlow CP, Rothwell PM.
Very early risk of stroke after a first transient ischaemic attack. Stroke 2003;
34:138-140.
3. Johnston SC, Gress DR, Browner WS, Sidney S. Short term prognosis after
emergency department diagnosis of TIA. JAMA 2000; 284(22): 2901-2906.
4.Chandratheva A, Mehta Z, Geraghty OC, Marquardt L, Rothwell PM On
behalf of the Oxford Vascular Study. Population-based study of risk and
predictors of stroke in the first few hours after a TIA.Neurology 2009; 72: 1941-
1947.
5. Johnston SC, Rothwell PM, Nguyen-Huynh MN, Giles MF,Elkins JS,
Bernstein AL, Sidney S. Validation and refinement of scores to predict very early
stroke risk after transient ischaemic attack. Lancet 2007; 369: 283-292.
6. Royal College of Physicians Intercollegiate Stroke Working Party. National
clinical guidelines for stroke. 3rd
Edition, 2007. P47.
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INTRODUCTION - TIA V1 with changes

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