Cerebral plasticity after hypoglosso-facial anastomosis in facial palsy: a magnetoencephalography study

Abstract

Background.Hypoglosso-facial anastomosis (HFA) consists in suturing the proximal part of the hypoglossal nerve with the distal part of the facial nerve in patients with facial palsy. Axonal regrowth through the anastomosis makes it possible to restore facial motor skills, which become spontaneous after physiotherapy. This suggests cerebral plasticity. ObjectiveWe used magnetoencephalography (MEG) in a pilot study to test this hypothesis MethodsTwenty-one healthy volunteers (CTRL) and 12 patients after HFA performed 5 motor tasks with MEG and electromyographic recordings: eyelid closure, smile, tongue protraction, mastication and thumb flexion. For each task, we picked the location of the maximum source activity within the precentral gyrus. We calculated the distances between this location and the vertex for each task and a somatotopy index. ResultsThere was an interaction between the participants group and the task (F(4,124)=4.07, p=0.0039). In CTRL, the maximum source location was statistically different between smile and tongue tasks and between eyelid and tongue tasks (p<0.001). No such difference was observed in HFA (p=1.000). 90.5% of CTRL and 41.7% of HFA showed a normal somatotopy (p=0.0046). ConclusionsIn CTRL, the organization of the cortical motor areas was similar to that of Penfields motor Homunculus. In contrast, in HFA, eyelid closure, tongue protraction and smile areas were not significantly distinct. This supports the hypothesis of cerebral plasticity after HFA. The Ethical Committee of Paris Idf VI approved the study (CPP Ouest 6-CPP975-HPS2). Financial Disclosure Statement- This research has received funding from the "Fondation pour la Recherche Medicale" and from the "Fondation des Gueules Cassees". It was performed on a platform of the France Life Imaging network partly funded by the grant "ANR-11-INBS-0006" and by the program "Investissements davenir" ANR-10-IAIHU-06. The funding bodies had no role in the study design, the data collection, analysis or interpretation, or the article writing. - The authors have neither commercial association nor financial disclosure. Generative AI was not used