THE ELECTROENCEPHOLOGRAM AS AN AID IN REVEALING INTRACRANIAL ARTERIOVENOUS MALFORMATIONS

Routine electroencephalography was performed on 58 patients with an intracranial arteriovenous malformation. Local abnormal EEG findings were observed in 23 (40 %) of them, 15 (26 %) had a general abnormality, and in 20 (34 %) the EEG was normal. In two patients with a local abnormality the abnormality was contralateral to the AVM. There was no relation between EEG abnormality and age of patients or duration of the symptoms. The size and radiological density of the AVM were not related with the frequency of EEG abnormality, nor were any differences seen in the distribution of findings between the non-haemorrhagic, subarachnoid haemorrhage and intracerebral haemorrhage groups. In patients with a history of epileptic seizures abnormality of the EEG was more frequent (p < 0.05) than in those with no epileptic seizures. Parietal and temporal AVMs combined had a higher frequency (p < 0.001) of local EEG abnormalities than in those patients in whom the AVM was occipital, central or in the posterior fossa. EEG as a screening method for intracranial AVM is noted to reveal only 62% of those AVMs found by brain scanning. On the other hand, half of the patients in whom scanning failed (due to small size or temporal location of the AVM) the EEG showed a local abnormality.