Elsevier

Journal of Clinical Neuroscience

Volume 48, February 2018, Pages 191-195
Journal of Clinical Neuroscience

Tools and techniques
Intraoperative definition of bottom-of-sulcus dysplasia using intraoperative ultrasound and single depth electrode recording – A technical note

https://doi.org/10.1016/j.jocn.2017.10.045Get rights and content

Highlights

  • IUS is beneficial in localizing and delineating small BOSDs intra-operatively.

  • Visualization of depth electrode positioning by iUS ensures optimal EEG sampling.

  • Correlation between pre- and post-resection iUS helps in assessing completeness of resection.

  • Using a multimodal approach including iUS and ECoG in surgery for BOSD may improve seizure outcome.

  • Compared to iMRI, iUS is cheaper, widely available and allows imaging in real-time.

Abstract

Bottom of sulcus dysplasias (BOSDs) are localized focal cortical dysplasias (FCDs) centred on the bottom of a sulcus that can be highly epileptogenic, but difficult to delineate intraoperatively. We report on a patient with refractory epilepsy due to a BOSD, successfully resected with the aid of a multimodal surgical approach using neuronavigation based on MRI and PET, intraoperative ultrasound (iUS) and electrocorticography (ECoG) using depth electrodes. The lesion could be visualized on iUS showing an increase in echogenicity at the grey-white matter junction. IUS demonstrated the position of the depth electrode in relation to the lesion. Depth electrode recording showed almost continuous spiking. Thus, intraoperative imaging and electrophysiology helped confirm the exact location of the lesion. Post-resection ultrasound demonstrated the extent of the resection and depth electrode recording did not show any epileptiform activity. Thus, both techniques helped assess completeness of resection. The patient has been seizure free since surgery. Using a multimodal approach including iUS and ECoG is a helpful adjunct in surgery for BOSD and may improve seizure outcome.

Introduction

Bottom of sulcus dysplasias (BOSD) are a recently recognised cause of medication resistant epilepsy. These small focal cortical dysplasias can be difficult to visualize on standard magnetic resonance imaging (MRI), with many patient’s previously considered ‘lesion-negative’. Locating the lesion and its boundaries intraoperatively can be challenging. In this technical note, we present a multimodal surgical approach using neuronavigation based on MRI and PET, intraoperative ultrasound and electrocorticography (ECoG) using depth electrodes during resection of the lesion.

Section snippets

Illustrative case and description of technique

A 25 year-old right-handed man presented to our comprehensive epilepsy programme with a 20-year history of drug resistant epilepsy. Routine electroencephalogram (EEG) showed focal epileptiform discharges arising from the right medial centro-parietal region. Previous MRI had been reported as normal.

Discussion

Our patient showed the typical clinical [5] and imaging features [1], [6] of a BOSD. Harvey et al. [5] reported a considerably higher rate of seizure freedom after resection of BOSD compared to a recent meta-analysis [11] on surgical management of focal cortical dysplasia (FCD). Hence it may be that patients with BOSD have a particularly favourable prognosis with resections limited to the small MRI visible lesion. However, the accurate localization and delineation of these subtle lesions can be

Conclusion

In this patient with BOSD, a multimodal approach including iUS and ECoG was helpful. IUS was beneficial in localizing and delineating a small BOSD intra-operatively. Visualization of depth electrode positioning by iUS ensured optimal EEG sampling. Furthermore, iUS helped by assessing the adequacy of resection. Compared to iMRI, iUS is cheaper, widely available and allows imaging in real-time.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest

None.

Ethical approval and informed consent

No experimental procedure was used in this retrospective case study. Ethical approval was not required. The patient has consented to submission of this Technical Report to the journal.

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Cited by (4)

  • Advanced intraoperative ultrasound (ioUS) techniques in focal cortical dysplasia (FCD) surgery: A preliminary experience on a case series

    2020, Clinical Neurology and Neurosurgery
    Citation Excerpt :

    This subtle pattern may be erroneously underestimated during the preoperative MRI. Therefore it is mandatory to obtain high quality intraoperative images [27] and to register intracranial epileptic activity to reach complete FCD resection. Strain SE is relatively insensitive to parenchymal anisotropy, allowing a better definition of different FCD’s components.

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