Electronystagmogram is useful in the diagnosis of vertebrobasilar and carotid transient ischaemic attacks.

Electronystagmogram examination of patients with transient ischaemic attacks or infarcts in the carotid and vertebrobasilar system revealed significantly increased number of patients with reduced caloric response, abnormal optokinetic nystagmus, saccadic dysmetria and presence of central nystagmus in patients with ischaemia of the posterior circulation. Using the presence of such abnormality as criterion for confirming posterior circulation ischaemia in suspected cases, we have correctly identified 67% of cases of vertebrobasilar infarct, 44% of the transient ischaemic attacks, 83% of carotid infarct and 96% of the carotid transient ischaemic attacks. Electronystagmogram findings of brainstem/cerebrallar system abnormality were found in 36% of transient ischaemic attacks with vertigo, and 50% of infarcts associated with vertigo. Thus Electronystagmogram studies are useful in localising the site of lesion in patients with suspected vertebrobasilar disease or with ischaemic attacks of undetermined territory, and in differentiation of vertigo due to definite cerebrovascular disease from peripheral causes of vertigo.