Background

The background EEG may be normal, or may show focal slowing or attenuation over the region of the arteriovenous malformation.

Interictal

Focal interictal spikes or sharp waves may be seen, at the location of the arteriovenous malformation.

Activation

EEG abnormality is enhanced by sleep deprivation, in drowsiness and in sleep.

CAUTION hyperventilation causes cerebral vasoconstriction, which may, in certain circumstances, impair critical cerebral perfusion and cause neurological symptoms. Hyperventilation is best avoided in the presence of intracranial vascular malformations.

Ictal

Focal rhythmic epileptiform discharges occur during focal seizures, with spatial correlation with the arteriovenous malformation.