Multimodality localization of the sensorimotor cortex in pediatric patients undergoing epilepsy surgery: Clinical article

Department of Neurology, University of Washington, Seattle, Washington, USA.
Journal of Neurosurgery Pediatrics (Impact Factor: 1.48). 06/2012; 10(1):1-6. DOI: 10.3171/2012.3.PEDS11554
Source: PubMed


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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    • "One benefit of regression analysis, e.g., would be that partially confounded but orthogonal events/ regressors (such as due to overlapping upper-and lower-extremity movements) could be included in the analysis . Manual coding of multiple continuous, graded regressors, however , would be extremely time-consuming, and automated procedures are hence required (e.g., departing form approaches by Lachaux et al., 2007b; Miller et al., 2007a; Schalk et al., 2004; Wray et al., 2012). Automate procedures for mapping the eloquent cortex based on natural behavior may not only use video and EMG signals, but can benefit from additional motion capture data (Ziegler et al., 2011 "
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    ABSTRACT: Precise delineation of pathological and eloquent cortices is essential in pre-neurosurgical diagnostics of epilepsy. A limitation of existing experimental procedures, however, is that they critically require active cooperation of the patient, which is not always achievable, particularly in infants and in patients with insufficient cognitive abilities. In the present study, we evaluated the potential of electrocorticographic recordings of high gamma activity during natural, non-experimental behavior of epilepsy patients to localize upper- and lower-extremity motor and language functions, and compared the results with those obtained using electrocortical stimulation. The observed effects were highly significant and functionally specific, and agreed well with the somatotopic organization of the motor cortex, both on the lateral convexity and in the supplementary motor area. Our approach showed a similar specificity and sensitivity for extremity movements as previously obtained from experimental data. We were able to quantify, for the first time, sensitivity and specificity of high gamma underlying non-experimental lower-extremity movements in four patients, and observed values in the same range as for upper extremities (analyzed in six patients). Speech-related responses in the three investigated patients, however, exhibited only a very low sensitivity. The present findings indicate that localization of not only upper- but also lower-extremity movements congruent with electrocortical stimulation mapping is possible based on event-related high gamma responses that can be observed during natural behavior. Thus, non-experimental mapping may be usefully applied as adjunct to established clinical procedures for identification of both upper- and lower-extremity motor functions.
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    ABSTRACT: Transcranial magnetic stimulation (TMS) is a neurostimulation and neuromodulation technique that has provided over two decades of data in focal, non-invasive brain stimulation based on the principles of electromagnetic induction. Its minimal risk, excellent tolerability and increasingly sophisticated ability to interrogate neurophysiology and plasticity make it an enviable technology for use in pediatric research with future extension into therapeutic trials. While adult trials show promise in using TMS as a novel, non-invasive, non-pharmacologic diagnostic and therapeutic tool in a variety of nervous system disorders, its use in children is only just emerging. TMS represents an exciting advancement to better understand and improve outcomes from disorders of the developing brain.
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    ABSTRACT: Transcranial magnetic stimulation (TMS) is rapidly gaining interest and momentum in the pediatric research world as a safe and effective method of non-invasive brain stimulation. Its applications span widely from mapping developmental neurophysiology to diagnosing and treating various neurological, psychiatric and medical disorders in children. This chapter will highlight the current and emerging applications of TMS in the pediatric population. Methods of TMS (including single pulse, paired-pulse and repetitive TMS) will be reviewed as well as alterations in techniques as applicable to the comfort and safety of children. Evidence of the minimal risk of TMS use in children, including data regarding energy imparted by TMS, adverse events and safety data from various pediatric TMS studies will be discussed. We will also review studies of developmental neurophysiology including those examining motor pathway maturation in neurologically normal children as well as studies of cortical reorganization following central and peripheral nervous system injury. Following this, we will discuss the various fields with diagnostic and therapeutic applications of TMS in children including perinatal and childhood stroke, epilepsy, attention-deficit/hyperactivity disorder, Tourette syndrome and various other childhood central nervous system diseases. The chapter will conclude with a discussion on emerging TMS applications in children including image-guided neuronavigation, pre-neurosurgical evaluation and pediatric headache.
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