Transient ischaemic attacks and prevention of strokes

A transient ischaemic attack (TIA) is an acute loss of neurological function or monocular vision caused by ischaemia with symptoms lasting less than 24 h. This occurs in 10% of patients prior to the development of a stroke. The annual incidence is 30 per 100 000.

A TIA is caused by artery-to-artery emboli or cardiac emboli. The pathogenesis is the same as for embolic stroke and is discussed on page 65. The investigation and management of TIAs and small strokes from which a good recovery has been made is the same because both provide a potential opportunity to prevent a more major stroke.

Clinical features

These episodes are transient and therefore the diagnosis is made on the basis of the history. The onset is usually rapid over seconds or minutes. The resolution is more variable, with complete recovery in minutes to the full 24 h. A wide range of different clinical disturbances can occur. In considering them, it is important to distinguish whether they arise from the anterior circulation (the carotids) or the posterior circulation (the vertebral and basilar arteries).

Anterior circulation TIAs include:

amaurosis fugax (fleeting blindness) – loss of vision in one eye, ‘like a shutter coming down’

aphasia, or other language problems such as dyslexia or dysgraphia.

Posterior circulation TIAs include:

homonymous visual field loss

dysarthria

combined brain stem symptoms: vertigo, diplopia, dysphagia; these are rarely TIAs if they occur in isolation

bilateral weakness or sensory loss.

Anterior or posterior circulation TIAs include:

unilateral weakness affecting the face, arm or leg in isolation or combination

unilateral sensory loss affecting the face, arm or leg in isolation or combination.

TIAs rarely lead to blackouts or alteration of consciousness. If this occurs, alternative diagnoses should be considered.

Because TIAs are transient and alarming, it is often difficult for the patient to characterize them exactly. It is therefore common not to be certain whether visual loss was monocular, indicating amaurosis fugax, or hemianopic, indicating a posterior circulation TIA. If in any doubt, the investigations should be directed as for an anterior circulation event.

A history of risk factors for atheroma is important (see Table 1, p. 64). In young women, the type of oral contraceptive is important: the combined oestrogen–progestogen pill increases their risk by two to three times, but there is no increased risk with progesterone only.

Examination of a patient following a TIA usually reveals no neurological abnormalities. Occasionally a cholesterol embolus is seen on fundoscopy (Fig. 1). The cardiovascular system is more likely to reveal relevant abnormalities such as hypertension, hypertensive retinal changes, arrhythmias, heart murmur, signs of cardiac failure suggesting left ventricular dysfunction, loss of peripheral pulses and bruits.