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The value of additional electrodes when stereo-electroencephalography is inconclusive
Adeel Ilyas1,2,3, Laura Vilella3,4, Carlos E Restrepo1,2,3
1Department of Neurological Surgery, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Epilepsia
|January 24, 2024
Summary
Two-step intracranial EEG (iEEG) is beneficial for refining seizure-onset zone localization when the initial hypothesis is plausible. However, it offers minimal benefit for erroneous hypotheses, suggesting two-step SEEG should be used cautiously.
Area of Science:
- Neurosurgery
- Epileptology
- Neurophysiology
Background:
- Stereo-electroencephalography (SEEG) is crucial for localizing the seizure-onset zone (SOZ) in drug-resistant focal epilepsy.
- Occasionally, SEEG fails to confirm the pre-implantation hypothesis, necessitating further evaluation.
- The utility of unplanned two-step intracranial EEG (iEEG) in such scenarios remains under-characterized.
Purpose of the Study:
- To characterize outcomes following unplanned two-step iEEG procedures.
- To evaluate the benefits of adding SEEG electrodes (2sSEEG) or placing subdural electrodes (SDEs) after an initial SEEG (SEEG2SDE).
- To analyze the relationship between two-step iEEG benefits and clinical outcomes.
Main Methods:
- A retrospective review of 225 adult SEEG cases over 8 years.
- Independent quantification of benefits from additional intracranial electrodes by three raters.
- Analysis of the relationship between two-step iEEG benefits and clinical outcomes.
Main Results:
- Fourteen patients underwent 2sSEEG, and nine underwent SEEG2SDE.
- 2sSEEG was beneficial in 64% of cases, particularly for precise SOZ localization (100% benefit) versus non-localizable onsets (17% benefit).
- SEEG2SDE successfully identified the SOZ and delineated eloquent cortex margins in all cases.
Conclusions:
- Two-step iEEG is valuable for clarifying SOZ or surgical margins when the initial hypothesis is broadly concordant.
- Two-step SEEG offers minimal benefit for erroneous hypotheses and should be used cautiously.
- SEEG2SDE effectively delineates surgical boundaries relative to SOZ and eloquent cortex, minimizing the need for SDEs.
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