Exploratory Study of the Central Nervous System Response in Facial Synkinesis after Bell’s Palsy
Natalie Ann Krane, MD; Alexander Stevens, PhD; Matthew Hill, MS; Myriam D Loyo, MD;
Oregon Health & Science University, Portland, OR
INTRODUCTION Facial synkinesis is the coupling of unintentional facial movements with those that are intentional, generally involving the periocular, midface, perioral, chin and neck muscles. Facial synkinesis develops weeks or months after facial nerve injury, and is most commonly seen after idiopathic facial nerve injury, e.g. Bell's palsy (BP). Commonly, patients with synkinesis attempt to close their eyes and experience unintentional lip movement or attempt to smile and experience unintentional eye closure. Synkinesis is thought to occur secondary to both aberrant peripheral nerve regeneration and neuronal reorganization in the facial nucleus following recovery after the original facial nerve injury. Although there are data to support cortical reorganization in patients with BP, there are no such data in synkinesis. We used functional magnetic resonance imaging (fMRI) to characterize changes in the central nervous system (CNS) in synkinesis by studying changes in the motor cortex and sensorimotor integration regions during motor tasks that elicit facial synkinesis.
MATERIALS & METHODS: Fourteen patients with a history of BP (7 fully recovered, 7 with synkinesis) underwent clinical assessment of their facial function and completed the validated Synkinesis Assessment Questionnaire and Edinburgh Inventory forms. They then performed a series of facial motor tasks, alternating between blinking, smiling and a baseline rest condition, while undergoing fMRI scans in a 3 Tesla Siemens Prisma scanner.
RESULTS: As a group, the recovered BP subjects produced extensive activation when smiling and blinking in bilateral basal ganglia, as well as in premotor and motor cortical areas. The synkinesis group showed similar patterns in basal ganglia, premotor and motor cortical areas, but activation was generally weaker as compared to the fully recovered participants. Additionally, the synkinesis group had little differential activity when producing smiles versus blinks when compared to the BP group, which again had robust activation in precentral motor areas. Additional results will be presented.
DISCUSSION: Preliminary results suggest that facial synkinesis is associated with alteration in cortical areas involved in motor preparation and execution. fMRI can provide substantial insight into CNS changes as a consequence of synkinesis. Given the abnormal CNS activity in synkinesis observed in this study, fMRI may be a useful tool to further understand the therapeutic utility associated with therapies that enhance motor control and sensorimotor integration, such as proprioceptive-based training and mirror facial exercises.
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