Presurgical brain mapping of the language network in pediatric patients with epilepsy using resting-state fMRI

Abstract

OBJECTIVEEpilepsy affects neural processing and often causes intra- or interhemispheric language reorganization, rendering localization solely based on anatomical landmarks (e.g., Broca’s area) unreliable. Preoperative brain mapping is necessary to weigh the risk of resection with the risk of postoperative deficit. However, the use of conventional mapping methods (e.g., somatosensory stimulation, task-based functional MRI [fMRI]) in pediatric patients is technically difficult due to low compliance and their unique neurophysiology. Resting-state fMRI (rs-fMRI), a “task-free” technique based on the neural activity of the brain at rest, has the potential to overcome these limitations. The authors hypothesized that language networks can be identified from rs-fMRI by applying functional connectivity analyses.METHODSCases in which both task-based fMRI and rs-fMRI were acquired as part of the preoperative clinical protocol for epilepsy surgery were reviewed. Task-based fMRI consisted of 2 language tasks and 1 motor task. Resting-state fMRI data were acquired while the patients watched an animated movie and were analyzed using independent component analysis (i.e., data-driven method). The authors extracted language networks from rs-fMRI data by performing a similarity analysis with functionally defined language network templates via a template-matching procedure. The Dice coefficient was used to quantify the overlap.RESULTSThirteen children underwent conventional task-based fMRI (e.g., verb generation, object naming), rs-fMRI, and structural imaging at 1.5T. The language components with the highest overlap with the language templates were identified for each patient. Language lateralization results from task-based fMRI and rs-fMRI mapping were comparable, with good concordance in most cases. Resting-state fMRI–derived language maps indicated that language was on the left in 4 patients (31%), on the right in 5 patients (38%), and bilateral in 4 patients (31%). In some cases, rs-fMRI indicated a more extensive language representation.CONCLUSIONSResting-state fMRI–derived language network data were identified at the patient level using a template-matching method. More than half of the patients in this study presented with atypical language lateralization, emphasizing the need for mapping. Overall, these data suggest that this technique may be used to preoperatively identify language networks in pediatric patients. It may also optimize presurgical planning of electrode placement and thereby guide the surgeon’s approach to the epileptogenic zone.

Resting State fMRI for Motor Cortex Mapping in Children with Epilepsy

“…One study using ICA analysis of rsfMRI to delineate sensorimotor cortex in healthy adults and in four brain tumor patients showed the feasibility of the approach (16). Other studies have used ICA analysis for language mapping and compared it to task data, showing modest concordance (13, 15). We generated the IC and further processed them in native space.…”

Resting‐state functional MRI for motor cortex mapping in childhood‐onset focal epilepsy

“…14 Other studies have used ICA analysis for language mapping and compared it to task data, showing modest concordance. 12,30 One of the clinically relevant aspects of our approach is that we gen- ual centers. 20 Lu et al 13 validated the DICI method for identifying language network in 10 adult controls and 7 patients with brain tumors.…”

“…One study using ICA analysis of rsfMRI to delineate sensorimotor cortex in healthy adults and in four brain tumor patients showed the feasibility of the approach 14 . Other studies have used ICA analysis for language mapping and compared it to task data, showing modest concordance 12,30 …”

Advanced neuroimaging techniques in epilepsy

“…Contrary to task-based fMRI, resting-state fMRI (rs-fMRI) may also be acquired in very young patients, or in people who are cognitively impaired. Hemispheric dominance derived from rs-fMRI shows good concordance with task-based fMRI in both adult and paediatric epilepsy patients [30 ▪ ,31 ▪ ]. An important extension of these studies would be to explore whether rs-fMRI can be used to accurately predict language outcome following epilepsy surgery.…”