Risks and benefits of invasive epilepsy surgery workup with implanted subdural and depth electrodes.
OBJECTIVE
In patients with pharmacoresistant focal-onset seizures, invasive presurgical workup can identify epilepsy surgery options when noninvasive workup has failed. Yet, the potential benefit must be balanced with procedure-related risks. This study examines risks associated with the implantation of subdural strip and grid, and intracerebral depth electrodes. Benefit of invasive monitoring is measured by seizure outcomes. Diagnostic procedures made possible by electrode implantation are described.


METHODS
Retrospective evaluation of invasive workups in 242 epilepsy surgery candidates and additional 18 patients with primary brain tumors implanted for mapping only. Complications are scaled in five grades of severity. A regression analysis identifies risk factors for complications. Outcome is classified according to Engel's classification.


RESULTS
Complications of any type were documented in 23% of patients, and complications requiring surgical revision in 9%. We did not find permanent morbidity or mortality. Major risk factor for complications was the implantation of grids and the implantation of electrode assemblies comprising strip and grid electrodes. Depth electrodes were significantly correlated with a lower risk. Tumors were not correlated with higher complication rates. Chronic invasive monitoring of 3-40 days allowed seizure detection in 99.2% of patients with epilepsy and additional extensive mapping procedures. Patients with epilepsy with follow-up >24 months (n = 165) had an Engel class 1a outcome in 49.7% if epilepsy surgery was performed, but only 6.3% when surgery was rejected.


CONCLUSIONS
The benefit of chronic invasive workup outweighs its risks, but complexity of implantations should be kept to a minimum.
Ruhr-Epileptology, Department of Neurology, University Hospital Knappschaftskrankenhaus, Bochum, Germany. joerg.wellmer@kk-bochum.de
Jörg
J
Wellmer
Ferdinand
F
von der Groeben
Ute
U
Klarmann
Christian
C
Weber
Christian E
CE
Elger
Horst
H
Urbach
Hans
H
Clusmann
Marec
M
von Lehe
D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping / Q000009:adverse effects / Q000379:methods; D002648:Child; D002675:Child, Preschool; D004567:Electrodes, Implanted / Q000009:adverse effects*; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D036542:Tomography, Spiral Computed; D055815:Young Adult