Functional Magnetic Resonance Imaging in Patients undergoing Reanimating Surgery for Unilateral Facial Paralysis : Functional localizer study and pilot data

Introduction: Facial palsy refers to a condition in which the function of the facial nerve or the mimic musculature is partially or completely injured and this may result in enormous functional, psychological, and cosmetic problems for the patient. An often reported complaint is asymmetrical facial expression and lack of ability to smile. Nowadays it is possible to help these patients with reanimating facial surgery and provide them with more symmetry, a new smile and eye closure. For smile reconstruction, one can transplant a muscle into the affected side and connect it to a local nerve. There are two main ways for innervations. The first uses the facial nerve from the healthy face side which is extended with a nerve graft to the affected side. The other way is to use a branch of the trigeminal nerve. The latter group of patients will have to be trained to produces a smile while making a clenching movement because the nerve used is not normally involved in smiling. However for both procedures patients report spontaneously smiling after recovery. The question arises if there is evidence for cortical brain plasticity and which cortical regions are responsible for the spontaneous smiling. This report focused on a functional localizer study and pilot data obtained to get closer to solving this issue. Material and methods: Five healthy volunteers (three males, two females) have been scanned for the localizer study. Their primary motor cortex activity was assessed during a smiling, clenching and tapping task with functional magnetic resonance imaging. The same paradigm was used on 3 female patients suffering from a unilateral left sided facial palsy. Each patient was in a different stage of disease (one pre-operatively, two post-operatively). One of the post-operatively patients underwent a cross facial nerve graft procedure and the other had a lengthening temporalis myoplasty. We performed conjunctional analyses on all functional data. Also we compared the blood oxygenation level dependant (BOLD) signals of the patients with the subjects of the localizer group. Results: In the healthy subjects for the localizer study we found bilateral activation in the motor cortex. We were able to identify 3 significant (p<0.05 Bonferroni corrected) separate brain areas dedicated to the three tasks described above. However the smiling and clenching areas were closely related. In the pre-operatively patient we saw no significant activation on the right hemisphere while smiling. The patient with the CFNG showed significant activation while smiling but had a significant (p