Data available to date suggests segregation of patients with occlusive carotid disease into two broad categories; those with and those without symptoms. This classification is clinically useful as it ties in with the results of the carotid endarterectomy trials. However, there are limitations to this classification as it is clinically difficult to decide if a patient is truly asymptomatic. First, not all embolic episodes will be detected in the awake patient, it is a matter of `Russian roulette' which part of the brain is damaged. And secondly, most transient ischaemic attacks last a very brief time, so that the patient may not recall them, or they may occur while the patient is asleep, which may be one third of the day. Symptoms may be noted but be wrongly interpreted. We frequently encounter `asymptomatic' patients with evidence of cerebral infarction on computerized tomographic or magnetic resonance scanning.
There is also difficulty in deciding what to advise a patient who has a total occlusion on one side with or without a stroke, who also has an `asymptomatic' stenosis on the contralateral side. How should the contra-lateral stenosis be managed?
Following is a summary of what is known regarding the natural history of symptomatic and asymptomatic carotid stenosis.