Intracranial electroencephalography with subdural grid electrodes: techniques, complications, and outcomes.
OBJECTIVE
Intracranial subdural grid monitoring is a useful diagnostic technique for surgical localization in patients with intractable partial epilepsy. The rationale for the present study was to assess the morbidity of intracranial recordings and the surgical outcomes.


METHODS
We retrospectively reviewed the clinical data for 189 unique patients undergoing 198 intracranial subdural grid monitoring sessions between 1996 and 2004 at a tertiary epilepsy center.


RESULTS
The mean age of patients undergoing monitoring was 28 +/- 14 years. An average of 63 +/- 23 electrodes were inserted. The mean duration of monitoring was 8 +/- 4 days. Localization of an epileptogenic zone occurred in 156 sessions (79%) resulting in 136 resections (69%). There were 13 major complications (6.6%), including five infections and six hematomas. Three patients (1.5%) developed permanent deficits related to implantation. Sixty-two (47%) of 136 patients undergoing resection were seizure-free after resection. An additional 38 patients (28%) had a significant reduction in seizures. The mean follow-up was 51 +/- 30 months. The duration of monitoring, bone flap replacement, number of electrodes, and perioperative corticosteroids were not associated with infection or complication.


CONCLUSIONS
Subdural grid monitoring for identification an epileptogenic focus is high yield, revealing a focus in 79% of monitoring sessions. Complications rarely result in permanent morbidity (1.5%). Surgical outcome indicated that 74% of patients experienced a favorable reduction in seizure tendency.
Van Gompel
Jamie J
JJ
Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota 55905, USA.
Worrell
Gregory A
GA
Bell
Michael L
ML
Patrick
Todd A
TA
Cascino
Gregory D
GD
Raffel
Corey
C
Marsh
W Richard
WR
Meyer
Fredric B
FB
D000293:Adolescent; D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004567:Electrodes, Implanted / Q000009:adverse effects*; D004569:Electroencephalography / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000009:adverse effects / Q000379:methods; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D013355:Subdural Space / Q000502:physiology* / Q000601:surgery; D016896:Treatment Outcome; D055815:Young Adult