Abstracts

Rationale: Introduction It has been our observation that in most cases admitted to the epilepsy monitoring unit (EMU), seizure frequency reduces when patients undergo intracranial placement of electrodes for epilepsy surgery evaluation. Methods: Methods Patients with medically-intractable epilepsy admitted to the EMU, between April 2008 and March 2010, were included in the study. Their seizure frequency during scalp video-EEG evaluation was compared with that seen during video-EEG with intracranially-placed electrodes. Patients with status epilepticus were excluded. Demographic and clinical variables, location of epileptogenic focus, number of electrodes, length of stay, number of lobes recorded, and presence of complications, were taken into account. Results: Results 50 patients (25 female), with a mean age of 35.8 (range: 17-59), were included. Most were non-lesional (41 had normal MRI). All patients had subdurally-implanted strips, 2 had additional grid, and one patient additional depth electrodes. Mean number of electrodes was 96 ( /- 43). Seventeen had unilateral coverage and 33 bilateral, with an average of 3 lobes covered. 61% had an epileptogenic focus in the temporal lobe(s) (25% right, 29% left, 7% bilateral), 25& frontal, 5% occipital, 5% parietal, and 4% had multifocal epilepsy. Average length of stay was 15 days ( /- 9.4). Seizure frequency was 7% less with intracranial electrodes as compared with scalp video-EEG (p<0.05). Conclusions: Conclusion The benefit of intracranially-placed electrodes in localizing the epileptogenic focus is clear, but the finding that they may decrease seizure frequency, indicates the need of prolonged recordings.