Neuroplastic Mechanisms Underlying Facial Symmetry Recovery: Insights from Rich-Club Organization and SC-FC Coupling.

Abstract

Introduction: Unilateral facial paralysis is a condition marked by facial asymmetry. Although reconstructive surgeries, such as masseteric-to-facial nerve transfer combined with static suspension, significantly improve facial symmetry, patient outcomes can vary considerably. This study aims to explore cerebral reorganization, focusing on rich-club (RC) organization and SC-FC coupling as potential biomarkers for facial symmetry recovery.

Methods: We enrolled 40 patients with severe oral commissure drooping due to unilateral facial nerve lesions who underwent masseteric-to-facial nerve transfer combined with static suspension. Using fMRI and DTI, we analyzed rich-club properties, the macroscale structural connectivity (SC), and functional connectivity (FC). Based on postoperative symmetry levels, patients were categorized into symmetry and asymmetry groups for comparison.

Results: Patients with better facial symmetry demonstrated stronger SC-FC coupling and enhanced strength from rich-club nodes. Additionally, greater strength in non- rich-club nodes, along with stronger feeder and local edges, played a compensatory role in improving facial symmetry. In contrast, patients with facial asymmetry exhibited increasing FC in rich- and non-rich-club nodes, possibly as a maladaptive compensatory mechanism.

Conclusion: Our study highlights rich-club organization and SC-FC coupling as potential biomarkers for assessing and monitoring facial symmetry recovery in facial paralysis patients post-surgery. These findings offer valuable insights into the brain's adaptive responses, serving as sensitive indicators of disease symptomatology and functional performance.