Tools and techniquesIntraoperative definition of bottom-of-sulcus dysplasia using intraoperative ultrasound and single depth electrode recording – A technical note
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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Advanced intraoperative ultrasound (ioUS) techniques in focal cortical dysplasia (FCD) surgery: A preliminary experience on a case series
2020, Clinical Neurology and NeurosurgeryCitation 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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