Article
Invasive presurgical evaluation in 100 epilepsy patients using a total of 342 subdural interhemispheric electrodes (IHE): risk and benefits
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Authors
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Daniel Delev
- Department of Neurosurgery, University of Bonn, University Medical Center, Germany
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Knut Send
- Department of Neurosurgery, University of Bonn, University Medical Center, Germany
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Michael Malter
- Department of Epileptology, University of Bonn, University Medical Center, Germany
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Yaroslav Parpaley
- Department of Neurosurgery, University of Bonn, University Medical Center, Germany; Department of Neurosurgery, University Clinic Bochum, Germany
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Johannes Schramm
- Department of Neurosurgery, University of Bonn, University Medical Center, Germany
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Alexander Grote
- Department of Neurosurgery, University of Bonn, University Medical Center, Germany
| Published: | May 13, 2014 |
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Outline
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Objective: Surgery is a well-established and safe treatment option for focal drug resistant epilepsy. Difficulties in the identification of an epileptogenic focus localized in the mesial cortex are often encountered. The aim of the study was to evaluate feasibility, overall complication rate and diagnostic benefits after implantation of a difficult subgroup of subdural electrodes – interhemispheric electrodes (IHE) – as part of an invasive presurgical evaluation in epilepsy patients.
Method: A total of 100 patients, who underwent implantation of subdural IHEs during the period from 1989 until 2011, were included in the study. Data on surgical complications (intra- and postoperative), number of subdural electrodes and contacts, duration of invasive EEG-recording were collected and analyzed. The benefits (focus identification/exclusion and cortical mapping) from the IHEs could be evaluated in 94 patients, where invasive EEG data were available.
Results: A total of 342 stripe subdural electrodes (median 3; range 1–8) with overall 1466 contacts (median 12, range 4–40) were implanted. There were 4 postoperative complications – 2 contusions, which led to a temporary mild hemiparesis and 2 hematomas without clinical relevance. Both neurological impairments resolved completely until discharge, thus no permanent neurological deficits or severe sequalae could be observed. In 47 patients (50%) the epileptogenic focus could be detected by the IHE. Cortical mapping by using the IHEs was achieved in 34 cases (36%). In 44 patients the IHEs were used for excluding a mesial epileptogenic focus. In 65 patients (69%) the subsequent surgical procedure was changed because of the results from the IHEs – in 51 (54%) cases the surgery was accordingly extended or tailored and 14 (15%) cases were outright rejected for surgery. Favorable seizure outcome (ILAE1-ILAE3) could be achieved 65% (n=54) of the cases submitted to surgery.
Conclusions: Implantation of IHE for the preoperative evaluation of epilepsy patients is an accepted surgical procedure. It shows a low complication profile with 4% postoperative complications. Additionally, the evaluation of the invasive EEG data delivered from the IHEs influenced the further surgical procedure in 69% of the cases, thus demonstrating the diagnostic usefulness of this technically demanding subgroup of subdural electrodes for presurgical evaluation.
