CLINICAL ARTICLE J Neurosurg Pediatr 22:270–275, 2018 F unctional connectivity MRI (fcMRI)—a method of analyzing blood oxygen level–dependent (BOLD) signal in a task-free, resting-state paradigm—can provide insight into regional connectivity in both the in- tact and diseased brain. In healthy controls, fcMRI reveals compartmentalization of neuronal networks into specifc functional systems, such as sensorimotor, visual, audito- ry, dorsal attention, and default mode network (DMN). 1,7 While task-based fMRI is routinely used as part of the clinical presurgical evaluation of pediatric epilepsy pa- tients, fcMRI is an emerging addition to the imaging ar- mamentarium. Several studies have addressed the question of fcMRI connectivity in epilepsy, 5 including in temporal lobe epilepsy (TLE) cases. 10 These studies, summarized in Mankinen et al., 10 compared connectivity in patients ver- sus healthy controls, thus using a between-subjects design. Although these studies found connectivity abnormalities in a number of networks at a population level, they did not address lateralizing changes in resting-state fcMRI in the individual patient. Constable et al. recently reviewed the potential use and challenges of functional connectivity mapping in intrac- table epilepsy. 6 The most common method used in fcMRI processing is seed-based analysis. Seed-based analysis es- ABBREVIATIONS BOLD = blood oxygen level–dependent; DMN = default mode network; fcMRI = functional connectivity MRI; MNI = Montreal Neurological Institute; MTS = mesial temporal sclerosis; ROI = region of interest; TLE = temporal lobe epilepsy. SUBMITTED December 11, 2017. ACCEPTED March 29, 2018. INCLUDE WHEN CITING Published online June 22, 2018; DOI: 10.3171/2018.3.PEDS17701. Changes in resting-state connectivity in pediatric temporal lobe epilepsy Fabio Grassia, MD, 1 Andrew V. Poliakov, PhD, 2,4 Sandra L. Poliachik, PhD, 2,4 Kaitlyn Casimo, 2 Seth D. Friedman, PhD, 2 Hillary Shurtleff, PhD, ABPP, 3 Carlo Giussani, MD, PhD, 1 Edward J. Novotny Jr., MD, 3 Jeffrey G. Ojemann, MD, 4,5 and Jason S. Hauptman, MD, PhD 4,5 1 Department of Neurological Surgery, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy; Departments of 2 Radiology and 3 Neurology, Seattle Children’s Hospital; 4 Department of Neurological Surgery, University of Washington; and 5 Department of Neurosurgery, Seattle Children’s Hospital, Seattle, Washington OBJECTIVE Functional connectivity magnetic resonance imaging (fcMRI) is a form of fMRI that allows for analysis of blood oxygen level–dependent signal changes within a task-free, resting paradigm. This technique has been shown to have ef fcacy in evaluating network connectivity changes with epilepsy. Presurgical data from patients with unilateral temporal lobe epilepsy were evaluated using the fcMRI technique to defne connectivity changes within and between the diseased and healthy temporal lobes using a within-subjects design. METHODS Using presurgical fcMRI data from pediatric patients with unilateral temporal lobe epilepsy, the authors per- formed seed-based analyses within the diseased and healthy temporal lobes. Connectivity within and between temporal lobe seeds was measured and compared. RESULTS In the cohort studied, local ipsilateral temporal lobe connectivity was signifcantly increased on the diseased side compared to the healthy temporal lobe. Connectivity of the diseased side to the healthy side, on the other hand, was signifcantly reduced when compared to connectivity of the healthy side to the diseased temporal lobe. A statistically signifcant regression was observed when comparing the changes in local ipsilateral temporal lobe connectivity to the changes in inter–temporal lobe connectivity. A statistically signifcant difference was also noted in ipsilateral connectivity changes between patients with and those without mesial temporal sclerosis. CONCLUSIONS Using fcMRI, signifcant changes in ipsilateral temporal lobe and inter–temporal lobe connectivity can be appreciated in unilateral temporal lobe epilepsy. Furthermore, fcMRI may have a role in the presurgical evaluation of patients with intractable temporal lobe epilepsy. https://thejns.org/doi/abs/10.3171/2018.3.PEDS17701 KEYWORDS temporal lobe epilepsy; functional connectivity MRI; surgical technique J Neurosurg Pediatr Volume 22 • September 2018 270 ©AANS 2018, except where prohibited by US copyright law