Supplementary implantation of intracranial electrodes in the evaluation for epilepsy surgery
Received 21 February 2009; received in revised form 6 June 2009; accepted 11 July 2009.
Summary
Purpose
In some patients, resective epilepsy surgery can be planned based on a non-invasive work-up. However, in many cases, invasive monitoring with intracranial electrodes is required prior to recommending a resective procedure. Although the results of intracranial recordings are usually conclusive, a small group of patients may require additional electrodes to better define the seizure onset or propagation.
Methods
One hundred and seventy seven patients who underwent intracranial electrode insertion between January 2000 and June 2005 were reviewed. Twelve of these patients required a supplementary implantation prior to making a recommendation about resective surgery. We report the nature of implantation as well as the outcomes in these 12 patients.
Results
The mean age of these patients was 35 years (7 males). An average of 2.5 additional strip electrodes were required resulting in a mean of 9 strip type electrodes per patient, for a mean total of an additional 20 days. For most patients (9/12) this subsequent procedure identified an area of epileptic cortex other than that originally hypothesized. Seven patients went on to surgery of which three experienced a significant improvement in seizure control.
Conclusions
The addition of supplementary electrodes to an ongoing invasive electrode investigation can be a useful means of clarifying a patient's suitability for a resective surgical procedure. While the surgical outcomes may not be as favorable as in patients in whom the investigations are simpler, a proportion of these patients do benefit from the eventual resective procedure. In cases where the supplementary electrodes lead to the conclusion that surgery is not indicated, these patients can be satisfied that the surgical option has been explored to the fullest extent possible.
ABSTRACT