Secondary prevention of transient ischaemic attack and stroke.(ABC of Arterial and Venous Disease)

Stroke or transient ischaemic attack is common and likely to be fatal or cause serious disability. A second stroke will not necessarily be of the same type as the initial event, although haemorrhages tend to recur. Patients with previous stroke commonly succumb to other vascular events, in particular myocardial infarction. Effective secondary prevention depends on giving attention to all modifiable risk factors for stroke as well as treating the causes of the initial stroke. Four questions should be answered:

Is it acute cerebrovascular disease?

The key features of acute cerebrovascular disease are focal neurological deficit, sudden onset, and absence of an alternative explanation. Abrupt onset of a dense hemiparesis before gradual improvement in a conscious patient rarely causes doubt, but conditions which commonly mimic stroke must be considered (see previous article BMJ 2000;320:920-3).

Is it ischaemic or haemorrhagic stroke?

Neither clinical history nor examination can reliably distinguish infarction from primary intracerebral haemorrhage. A small bleed can produce transient symptoms, although these rarely resolve within an hour.

Cerebral imaging is essential, and the choice and timing of the scan is important. Haemorrhage is immediately apparent on computed tomography, but its distinctive appearance becomes indistinguishable from infarction over a few weeks; for major symptoms, a computed tomogram taken within two weeks should still be diagnostic, but a small bleed may be missed after one week.

Magnetic resonance imaging has a greater sensitivity for brain stem, cerebellar, and small ischaemic strokes of the brain than computed tomography. It can also identify haemorrhagic stroke and remains diagnostic long after signs have become undetectable on computed tomography.

Cardioembolic or vascular aetiology?

Up to a quarter of ischaemic strokes are due to embolism from the heart or major vessels. In these patients, full anticoagulation should be considered. Embolic stroke can affect any vascular territory but can rarely be diagnosed conclusively. Certain features should prompt a search for an embolic source. Transthoracic echocardiography is usually adequate, but transoesophageal echocardiography is justified if the results are equivocal or the index of suspicion is high.

Anterior or posterior circulation?

The vertebrobasilar arteries supply the brain stem, cerebellum, and occipital lobes; the cerebral hemispheres are supplied through the carotid arteries. This distinction is important since carotid Doppler ultrasonography with a view…