Utility of depth electrode placement in the neurosurgical management of bottom-of-sulcus lesions: technical note

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OBJECTIVE

Small lesions at the depth of the sulcus, such as with bottom-of-sulcus focal cortical dysplasia, are not visible from the surface of the brain and can therefore be technically challenging to resect. In this technical note, the authors describe their method of using depth electrodes as landmarks for the subsequent resection of these exacting lesions.

METHODS

A retrospective review was performed on pediatric patients who had undergone invasive electroencephalography with depth electrodes that were subsequently used as guides for resection in the period between July 2015 and June 2017.

RESULTS

Ten patients (3–15 years old) met the criteria for this study. At the same time as invasive subdural grid and/or strip insertion, between 2 and 4 depth electrodes were placed using a hand-held frameless neuronavigation technique. Of the total 28 depth electrodes inserted, all were found within the targeted locations on postoperative imaging. There was 1 patient in whom an asymptomatic subarachnoid hemorrhage was demonstrated on postprocedural imaging. Depth electrodes aided in target identification in all 10 cases.

CONCLUSIONS

Depth electrodes placed at the time of invasive intracranial electrode implantation can be used to help localize, target, and resect primary zones of epileptogenesis caused by bottom-of-sulcus lesions.

ABBREVIATIONS BOSD = bottom-of-sulcus FCD; FCD = focal cortical dysplasia; IP = inferior-posterior; MRC = Medical Research Council; PET = positron emission tomography; SEEG = stereo electroencephalography.

Article Information

Correspondence James T. Rutka: The Hospital for Sick Children, University of Toronto, ON, Canada. james.rutka@sickkids.ca.

INCLUDE WHEN CITING Published online June 28, 2019; DOI: 10.3171/2019.4.PEDS18639.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Long biopsy guide tube (120 mm) from the BrainLAB frameless stereotactic set used for the insertion of depth electrodes. Figure is available in color online only.

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    Case 1. MR images showing a lesion with high FLAIR signal in the cortex and subcortical white matter (pink) in the left midcingulate gyrus and adjacent corticospinal tract (yellow). Figure is available in color online only.

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    Case 1. Intraoperative image of 2 depth electrodes and 1 interhemispheric strip electrode (IHI). ALD = anterior lesion depth; PLD = posterior lesion depth. Figure is available in color online only.

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    Case 1. Postoperative MR image with 2 depth electrodes and an interhemispheric strip electrode. Figure is available in color online only.

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    Case 2. MR images showing a subtle lesion with high T1 signal and blurring of the gray-white junction in the right frontal paracentral lobule (pink) suspicious for FCD. Corticospinal tract (yellow) and cerebral veins (purple). Figure is available in color online only.

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    Case 2. Intraoperative image of 64-contact grid, 1 strip electrode, and 2 depth electrodes. Figure is available in color online only.

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    Case 2. Postoperative MRI with 2 depth electrodes. ILD = inferior lesion depth; SLD = superior lesion depth. Figure is available in color online only.

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    Case 2. Intraoperative image of depth electrode–guided lesionectomy. Figure is available in color online only.

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    Case 3. MR image showing high T1-weighted signal in the cortex associated with blurring of the gray-white matter junction in the left postcentral gyrus and left superior parietal lobule (pink) suspicious for FCD. The lesion abuts the posterior aspect of the left corticospinal tract (yellow). Figure is available in color online only.

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    Case 3. Postoperative MR reconstructions of the lesion with depth electrodes in place. IA = inferior-anterior; IP = inferior-posterior; SA = superior-anterior; SP = superior-posterior. Figure is available in color online only.

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