EEG monitoring during endovascular embolization of cerebral arteriovenous malformations

Arteriovenous malformations (AVMs) may have a bad prognosis. Endovascular embolization with cyanocrylate represents nowadays an important initial step in a staged treatment, that later may include surgery or radiotherapy. Embolization may induce significant changes in the dynamics of the cerebral circulation, some of which may provoke neurological sequelae. Therefore assessment of potential complications is usually done by using a superselective amytal test, during which small doses of amytal are injected directly in the pedicle that is going to be embolized. In spite of an extensive use of the EEG during endovascular embolization its evaluation in terms of benefits and limitations is not available. Such evaluation is therefore the aim of this work. EEG monitoring was performed during endovascular embolization of 19 patients; a large majority of patients presented large AVMs, with Spetzler indexes around IV or V. The main results were as follows: (1) EEG changes at baseline were significantly correlated with the AVM size and the Spetzler index but were unable to predict the difficulties in the embolization; (2) during amytal tests EEG positivity reached 35% and consisted mainly in ipsilateral slow focal activity; (3) in some cases embolization was performed in spite of transient EEG changes. It was found that focal or diffuse abnormalities in the lower frequency range, even when slight, could be followed by clinical hazards (3 out of 11 cases); (4) EEG monitoring was important in the prediction, evaluation and prognosis of clinical complications.