Pediatric Language Mapping: Sensitivity of Neurostimulation and Wada Testing in Epilepsy Surgery

Abstract

Summary:Purpose: Functional mapping of eloquent cortex with electrical neurostimulation is used both intra-and extraoperatively to tailor resections. In pediatric patients, however, functional mapping studies frequently fail to localize language. Wada testing has also been reported to be less sensitive in children.Methods: Thirty children (4.7 -14.9 years) and 18 adult controls (18-59 years) who underwent extraoperative language mapping via implanted subdural electrodes at the NYU Comprehensive Epilepsy Center were included in the study. Ten children and 14 adults underwent preoperative Wada testing. Success of the procedures was defined as the identification of at least one language site by neurostimulation mapping and determination of hemispheric language dominance on the Wada test.Results: In children younger than 10.2 years, cortical stimulation identified language cortex at a lower rate than was seen in children older than 10.2 years and in adults (p < 0.05). This threshold, demonstrated by survival and χ 2 analysis, was sharply defined in our data set. Additionally, Wada testing was more likely to be successful than was extraoperative mapping in this younger age group (p < 0.05).Conclusions: Analysis of our series demonstrates that language cortex is less likely to be identified in children younger than 10 years, suggesting that alternatives to the current methods of cortical electrical stimulation, particularly the use of preoperative language lateralization, may be required in this age group.

Cortical Language Mapping in Epilepsy: A Critical Review

“…Interestingly, results of our adult studies have also suggested a greater number of positive language sites in older adults (Hamberger et al 2007). Schevon et al (2007) reported a significantly lower probability of identifying language cortex via ESM in children than in adults, with age 10 years as a sharply defined threshold. Overall, these results have been considered to reflect the development of new language foci with cortical maturation.…”

Language mapping in children using resting-state functional connectivity: comparison with a task-based approach

“…Furthermore, these invasive procedures require the patient to remain alert for language assessment, which is unfeasible in half of children with intractable epilepsy due to cognitive and behavioral problems. 1,5 Consequently, inconclusive results are reported in most patients younger than age 10 for ESM (up to 81%) and for IAT (50%). 5,6 In the past decade, noninvasive neuroimaging techniques, including functional magnetic resonance imaging (fMRI) [7][8][9][10][11] and magnetoencephalography (MEG), [12][13][14][15][16][17][18] have been widely used for language cerebral lateralization and mapping in adults and children.…”

“…As a result, these methods are often not available to these patients, which may rule out surgical treatment or increase the risk of postoperative deficits. 5,30 Resting-state functional connectivity is an alternative neuroimaging approach that is not subject to the limitations described above. It is a relatively a modern method for evaluating the regional interactions that occur in the brain when a subject is not performing an explicit task.…”

Extraoperative Functional Mapping and Staged Resection of Supratentorial Tumors near Eloquent Cortex in Children

“…Another possibility is diminished sensitivity of neurostimulation mapping in children younger than 10 years of age, due to a higher percentage of small and unmyelinated fibers requiring an increased charge density to elicit a response to stimulation [21]. The charge density is inversely proportional to the area being stimulated and is determined by the distance between electrodes with bipolar stimulation.…”

“…The charge density is inversely proportional to the area being stimulated and is determined by the distance between electrodes with bipolar stimulation. Thus, placing the contacts closer together increases the charge density without increasing the applied current [21]. To address this possibility, we now use custom 64-contact grids with 5 mm between electrodes (Adtech Inc.) for all pediatric patients.…”