Abstracts

Rationale: There is a paucity of data pertaining to complications and long-term seizure outcome in patients with invasive intracranial electrode monitoring and subsequent surgical resection.Methods: We retrospectively reviewed the clinical data for 92 adult patients who were monitored with intracranial subdural electrode monitoring sessions between 1991 and 2006. Results: The mean age at onset of epilepsy was 14 10 years. The mean age at surgery was 33 10 years, with a mean duration of epilepsy of 19 11 years. The mean duration of monitoring was 10 4 days. Seventy-two patients (78%) had discrete lesions identified on magnetic resonance imaging, 55 (60%) of which were temporal. Resections included a) lesionectomy (n=38; 41.3%), b) lesionectomy and resection of additional epileptogenic zone (n=15; 16.3%), c) limited resection of lesion (n=13; 14.1%), and d) resection of epileptogenic zone in nonlesional patients (n=15; 16.3%). Eleven patients (12%) did not have a surgical resection, six of whom seizure onset was not localizable. There were no deaths and seven (8%) major complications: three hematomas, three infections, and one infarction. The mean duration of follow up was 67 54 months. Thirty eight patients (47%) were seizure-free (Engel Class I) after surgical resection: 33 (50%) lesional and five (31%) nonlesional (p=0.615). Conclusions: Patients who have intracranial electroencephalography monitoring represent a distinct group of intractable epilepsy patients. The epileptogenic focus can be identified in the majority (93%) of patients. Although surgical resection may be limited by eloquent cortex, many patients experience a significant reduction in seizure frequency. Although lesional patients had a higher rate of seizure freedom, this difference was not statistically significant.