CLINICAL ARTICLE J Neurosurg 126:1181–1190, 2017 D iffuse low-grade gliomas (DLGGs) are slow- growing primitive brain tumors that occur pre- dominantly in so-called functional regions. Be- cause of their slow growth, they induce modifcations of the local activity and connectivity, representing a well- studied model of brain plasticity. Indeed, this plasticity is observed at different scales. 1) Some infltrated regions continue to keep their functionality. 2) Functional regions migrate to the periphery of the tumor. 3) Finally, there might be a contralateral functional compensation. These plasticity phenomena are observable before, during, and after surgery, and are the topic of this study in the spe- ABBREVIATIONS BOLD = blood-oxygen-level dependent; DLGG = diffuse low-grade glioma; fMRI = functional MRI; GRE-EPI = gradient echo–echo planar imaging; MNI = Montreal Neurological Institute; MP-RAGE = magnetization-prepared, rapid-acquisition gradient echo; SMA = supplementary motor area. SUBMITTED October 28, 2015. ACCEPTED April 12, 2016. INCLUDE WHEN CITING Published online June 17, 2016; DOI: 10.3171/2016.4.JNS152484. * Drs. Vassal and Charroud contributed equally to this work. Recovery of functional connectivity of the sensorimotor network after surgery for diffuse low-grade gliomas involving the supplementary motor area *Matthieu Vassal, MD, MSc, 1–4 Céline Charroud, PhD, 2,4 Jérémy Deverdun, PhD, 2–6 Emmanuelle Le Bars, PhD, 2,4,6 François Molino, PhD, 5,6 Francois Bonnetblanc, PhD, 7 Anthony Boyer, MSc, 7 Anirban Dutta, PhD, 7 Guillaume Herbet, PhD, 1,3 Sylvie Moritz-Gasser, PhD, 1,3 Alain Bonafé, MD, PhD, 2–4 Hugues Duffau, MD, PhD, 1,3 and Nicolas Menjot de Champfeur, MD, PhD 2–4,6 Departments of 1 Neurosurgery and 4 Neuroradiology, 2 Institut d’Imagerie Fonctionnelle Humaine, and 3 Institut des Neurosciences de Montpellier, INSERM U1051, Centre Hospitalier Régional Universitaire de Montpellier; and 5 Institut de Génomique Fonctionnelle, UMR 5203–INSERM U661, 6 Laboratoire Charles Coulomb, CNRS UMR 5221, and 7 Laboratoire d’Informatique, de Robotique et de Microélectronique de Montpellier, CNRS UMR5506, Université de Montpellier, Montpellier, France OBJECTIVE The supplementary motor area (SMA) syndrome is a well-studied lesional model of brain plasticity in- volving the sensorimotor network. Patients with diffuse low-grade gliomas in the SMA may exhibit this syndrome after resective surgery. They experience a temporary loss of motor function, which completely resolves within 3 months. The authors used functional MRI (fMRI) resting state analysis of the sensorimotor network to investigate large-scale brain plasticity between the immediate postoperative period and 3 months’ follow-up. METHODS Resting state fMRI was performed preoperatively, during the immediate postoperative period, and 3 months postoperatively in 6 patients with diffuse low-grade gliomas who underwent partial surgical excision of the SMA. Cor- relation analysis within the sensorimotor network was carried out on those 3 time points to study modifcations of its functional connectivity. RESULTS The results showed a large-scale reorganization of the sensorimotor network. Interhemispheric connectivity was decreased in the postoperative period, and increased again during the recovery process. Connectivity between the lesion side motor area and the contralateral SMA rose to higher values than in the preoperative period. Intrahemispheric connectivity was decreased during the immediate postoperative period and had returned to preoperative values at 3 months after surgery. CONCLUSIONS These results confrm the fndings reported in the existing literature on the plasticity of the SMA, show- ing large-scale modifcations of the sensorimotor network, at both inter- and intrahemispheric levels. They suggest that interhemispheric connectivity might be a correlate of SMA syndrome recovery. https://thejns.org/doi/abs/10.3171/2016.4.JNS152484 KEY WORDS magnetic resonance imaging; glioma; neuronal plasticity; paralysis; brain mapping; functional neuroimaging; oncology ©AANS, 2017 J Neurosurg Volume 126 • April 2017 1181