Interictal scalp electroencephalography and intraoperative electrocorticography in magnetic resonance imaging-negative temporal lobe epilepsy surgery.
OBJECTIVE
Scalp electroencephalography (EEG) and intraoperative electrocorticography (ECoG) are routinely used in the evaluation of magnetic resonance imaging-negative temporal lobe epilepsy (TLE) undergoing standard anterior temporal lobectomy with amygdalohippocampectomy (ATL), but the utility of interictal epileptiform discharge (IED) identification and its role in outcome are poorly defined.


OBJECTIVE
To determine whether the following are associated with surgical outcomes in patients with magnetic resonance imaging-negative TLE who underwent standard ATL: (1) unilateral-only IEDs on preoperative scalp EEG; (2) complete resection of tissue generating IEDs on ECoG; (3) complete resection of opioid-induced IEDs recorded on ECoG; and (4) location of IEDs recorded on ECoG.


METHODS
Data were gathered through retrospective medical record review at a tertiary referral center. Adult and pediatric patients with TLE who underwent standard ATL between January 1, 1990, and October 15, 2010, were considered for inclusion. Inclusion criteria were magnetic resonance imaging-negative TLE, standard ECoG performed at the time of surgery, and a minimum follow-up of 12 months. Univariate analysis was performed using log-rank time-to-event analysis. Variables reaching significance with log-rank testing were further analyzed using Cox proportional hazards.


METHODS
Excellent or nonexcellent outcome at time of last follow-up. An excellent outcome was defined as Engel class I and a nonexcellent outcome as Engel classes II through IV.


RESULTS
Eighty-seven patients met inclusion criteria, with 48 (55%) achieving an excellent outcome following ATL. Unilateral IEDs on scalp EEG (P = .001) and complete resection of brain regions generating IEDs on baseline intraoperative ECoG (P = .02) were associated with excellent outcomes in univariate analysis. Both were associated with excellent outcomes when analyzed with Cox proportional hazards (unilateral-only IEDs, relative risk = 0.31 [95% CI, 0.16-0.64]; complete resection of IEDs on baseline ECoG, relative risk = 0.39 [95% CI, 0.20-0.76]). Overall, 25 of 35 patients (71%) with both unilateral-only IEDs and complete resection of baseline ECoG IEDs had an excellent outcome.


CONCLUSIONS
Unilateral-only IEDs on preoperative scalp EEG and complete resection of IEDs on baseline ECoG are associated with better outcomes following standard ATL in magnetic resonance imaging-negative TLE. Prospective evaluation is needed to clarify the use of ECoG in tailoring temporal lobectomy.
Department of Neurology, Mayo Clinic, Rochester, Minnesota.
David B
DB
Burkholder
Department of Neurology, Mayo Clinic, Rochester, Minnesota2International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
Vlastimil
V
Sulc
Department of Neurology, Mayo Clinic, Rochester, Minnesota.
E Matthew
EM
Hoffman
Department of Neurology, Mayo Clinic, Rochester, Minnesota.
Gregory D
GD
Cascino
Department of Neurology, Mayo Clinic, Rochester, Minnesota.
Jeffrey W
JW
Britton
Department of Neurology, Mayo Clinic, Rochester, Minnesota.
Elson L
EL
So
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota.
W Richard
WR
Marsh
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota.
Fredric B
FB
Meyer
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota.
Jamie J
JJ
Van Gompel
Department of Pathology, Mayo Clinic, Rochester, Minnesota.
Caterina
C
Giannini
Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.
C Thomas
CT
Wass
Department of Radiology, Mayo Clinic, Rochester, Minnesota.
Robert E
RE
Watson
Department of Neurology, Mayo Clinic, Rochester, Minnesota7Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.
Gregory A
GA
Worrell
D000293:Adolescent; D000328:Adult; D038481:Anterior Temporal Lobectomy / Q000379:methods; D002648:Child; D004569:Electroencephalography / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011446:Prospective Studies; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult