Abstracts

Intracranial EEG recording is necessary in a subset of patients undergoing epilepsy surgery. This study evaluates the risk factors associated with morbidity and mortality during video-EEG monitoring with subdural electrodes in patients with intractable partial epilepsy. Retrospective audit of all patients undergoing monitoring with intracranial electrodes at Westmead Hospital and The Children[apos]s Hospital at Westmead between 1988-2004. The following variables were recorded: epilepsy syndrome, anticonvulsant medication, duration of implantation surgery and intracranial monitoring, side and site of grid implantation, number of grids and electrodes, size of grids, frequency of clinical seizures, previous craniotomy, other medical conditions and length of hospital stay. 296 patients with refractory epilepsy underwent epilepsy surgery during this period. 79 intracranial monitoring sessions were performed in 71 patients (49 males; median age: 24 years; IQR 17;35, range 6-54 years) to further localize the ictal onset. 69% had extratemporal epilepsy and 44% were non-lesional. Median monitoring duration 11 days (IQR 7;14). 82% of the monitored patients underwent epilepsy resection. 75% had seizure outcome of Engel 1 or 2 with a median follow up period of 31 months. Overall complication rate was 31.6%. 26.6% were directly related to subdural electrode implantation; 13.9% transient complications requiring no treatment, 8.9% transient complications requiring treatment, 1.3% permanent and there were 2 deaths (2.5%). Specific complications included osteomyelitis (2.5 %), haemorrhage (7.6%), cerebral infarction (3.8%), transient neurological deficit (5.1%) and pulmonary emboli or deep venous thrombosis (3.8%). The 2 deaths were both related to raised intracranial pressure (1 venous infarction, 1 unexplained) and occurred within 48 hrs of implantation. Complications were associated with greater number of electrodes (p[lt]0.001), greater number of strip/grid arrays (0.039), 8x8 grids (0.001) and longer duration of monitoring (0.029). Only the total number of electrodes was found to be statistically significant (p[lt]0.001) when fitted into a multiple logistic regression. No significant correlation existed between complications and seizure frequency, interhemispheric site, repositioning of electrodes or age. The transient complication rate in this series is comparable to previously reported series¹. We found increased morbidity and mortality were associated with a greater number of electrodes. The results of this audit are being used to modify our implantation and monitoring protocols.
1. Hamer HM, Morris HH, Mascha EJ et al. Complications of invasive video-EEG monitoring with subdural grid electrodes. [italic]Neurology [/italic]2002:58;97-103 (Supported by Sanofi Aventis Australia.)