Noninvasive imaging techniques to map language areas using BOLD signal fluctuations in pediatric epilepsy: a review

Accurate localization and lateralization of language areas are essential in the preoperative evaluation of children with drug-resistant epilepsy (DRE) to minimize postoperative neurological deficits. Traditional invasive methods such as the Wada test and electrocortical stimulation remain gold standards but present significant limitations, especially in pediatric populations. Noninvasive techniques leveraging blood oxygen level-dependent (BOLD) signal fluctuations, such as functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRS), offer interesting and convenient alternatives, but clinical evidence is limited. This narrative review aims to synthesize current knowledge on noninvasive BOLD-based imaging techniques, specifically task-based and resting-state fMRI and fNIRS, for language mapping in children with epilepsy.

A comprehensive literature search was conducted using PubMed, focusing on studies employing fMRI and fNIRS for language mapping in pediatric epilepsy and cross-referencing. Special consideration was given to higher-impact studies, frequently cited publications, and works by leading experts in the field.

Task-based fMRI remains the clinical standard for language mapping but is frequently compromised by poor task compliance in children. Resting-state fMRI provides a task-free alternative with high sensitivity but often yields broader, bilateral networks that complicate precise lateralization. fNIRS offers a portable and child-friendly option with excellent tolerability but is limited by its spatial resolution and depth penetration. Further standardization of the various data-processing methods used for these modalities is required.

BOLD-based noninvasive imaging techniques represent promising advancements in the preoperative evaluation of pediatric epilepsy surgery candidates. Future multicenter studies and the development of pediatric-specific tools are essential to establish standardized clinical use.