Multimodality localization of the sensorimotor cortex in pediatric patients undergoing epilepsy surgery
ABSTRACT The gold-standard method for determining cortical functional organization in the context of neurosurgical intervention is electrical cortical stimulation (ECS), which disrupts normal cortical function to evoke movement. This technique is imprecise, however, as motor responses are not limited to the precentral gyrus. Electrical cortical stimulation also can trigger seizures, is not always tolerated, and is often unsuccessful, especially in children. Alternatively, endogenous motor and sensory signals can be mapped by somatosensory evoked potentials (SSEPs), functional MRI (fMRI), and electrocorticography of high gamma (70-150 Hz) signal power, which reflect normal cortical function. The authors evaluated whether these 4 modalities of mapping sensorimotor function in children produce concurrent results.
The authors retrospectively examined the charts of all patients who underwent epilepsy surgery at Seattle Children's Hospital between July 20, 1999, and July 1, 2011, and they included all patients in whom the primary motor or somatosensory cortex was localized via 2 or more of the following tests: ECS, SSEP, fMRI, or high gamma electrocorticography (hgECoG).
Inclusion criteria were met by 50 patients, whose mean age at operation was 10.6 years. The youngest patient who underwent hgECoG mapping was 2 years and 10 months old, which is younger than any patient reported on in the literature. The authors localized the putative sensorimotor cortex most often with hgECoG, followed by SSEP and fMRI; ECS was most likely to fail to localize the sensorimotor cortex.
Electrical cortical stimulation, SSEP, fMRI, and hgECoG generally produced concordant localization of motor and sensory function in children. When attempting to localize the sensorimotor cortex in children, hgECoG was more likely to produce results, was faster, safer, and did not require cooperation. The hgECoG maps in pediatric patients are similar to those in adult patients published in the literature. The sensorimotor cortex can be mapped by hgECoG and fMRI in children younger than 3 years old to localize cortical function.
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ABSTRACT: We investigated the contribution of electrocortical stimulation (ECS), induced high gamma electrocorticography (hgECoG) and functional magnetic resonance imaging (fMRI) for the localization of somatosensory and language cortex.Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 04/2014; DOI:10.1016/j.clinph.2014.04.007 · 2.98 Impact Factor
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ABSTRACT: Accurate language localization expands surgical treatment options for epilepsy patients and reduces the risk of postsurgery language deficits. Electrical cortical stimulation mapping (ESM) is considered to be the clinical gold standard for language localization. While ESM affords clinically valuable results, it can be poorly tolerated by children, requires active participation and compliance, carries a risk of inducing seizures, is highly time consuming, and is labor intensive. Given these limitations, alternative and/or complementary functional localization methods such as analysis of electrocorticographic (ECoG) activity in high gamma frequency band in real time are needed to precisely identify eloquent cortex in children. In this case report, the authors examined 1) the use of real-time functional mapping (RTFM) for language localization in a high gamma frequency band derived from ECoG to guide surgery in an epileptic pediatric patient and 2) the relationship of RTFM mapping results to postsurgical language outcomes. The authors found that RTFM demonstrated relatively high sensitivity (75%) and high specificity (90%) when compared with ESM in a "next-neighbor" analysis. While overlapping with ESM in the superior temporal region, RTFM showed a few other areas of activation related to expressive language function, areas that were eventually resected during the surgery. The authors speculate that this resection may be associated with observed postsurgical expressive language deficits. With additional validation in more subjects, this finding would suggest that surgical planning and associated assessment of the risk/benefit ratio would benefit from information provided by RTFM mapping.Journal of Neurosurgery Pediatrics 07/2014; DOI:10.3171/2014.6.PEDS13477 · 1.37 Impact Factor
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ABSTRACT: The general principle of epilepsy surgery is to achieve seizure freedom without causing any neurological deficit that would outweigh the clinical benefit. To achieve this, the epileptogenic zone, which is the part of the brain responsible for seizure generation, as well as the anatomic location of the eloquent cortex must be precisely identified in order to spare those functions during excision of the epileptogenic tissue. Major technical advances over the last decade have continuously contributed to increase our ability to map the brain and identify these critical areas. These technologies and innovations that can be routinely used today include non--invasive studies such as magnetoencephalography (MEG), functional MRI (fMRI), simultaneous EEG-fMRI, and nuclear medicine based methods like PET and SPECT as well as invasive studies through chronically implanted electrodes. Electrodes can be either placed subdurally via burr holes and craniotomies or via frame--based and frameless stereotactic methods within the brain. Apart from a continuous change in these insertion techniques, the most valuable advances here include recordings on high frequency bandwidth (100-600 Hz EEG) that are capable to delineate high--frequency oscillations (HFOs). These HFOs have been recognized as a biomarker for epileptogenic tissue. All of these technical advances have made epilepsy surgery a truly multidisciplinary field and surgeons have to be able to understand and interpret all of the gathered data. Moreover, this development has influenced surgical approaches and techniques and epilepsy surgery today includes a wide variety of procedures. These can be subdivided into resective, disconnective and neuromodulation procedures and vary from a small, targeted lesionectomy to disconnection/resection of one hemisphere. This review will give an overview of the available surgical techniques today and will focus on how the technical advances enable us to map the brain and delineate the critical areas.Journal of neurosurgical sciences 02/2015; · 0.78 Impact Factor