Introduction: Differently from limb muscles, facial muscles motoneurons can be recruited by two descending motor pathways, one arising from the primary motor cortex and the second arising from the midcingulate area (1). Lesions involving the former pathway are associated to voluntary facial paresis, while lesions involving the latter are associated to emotional paresis (2). Patients suffering a voluntary facial paresis cannot voluntary smile, but for example they smile normally in response to jokes. On the contrary, patients suffering an emotional paresis can voluntarily mimic facial expressions, but are unable to produce spontaneous emotional expressions. During rehabilitation after facial nerve lesion, patients are commonly trained to produce symmetric and isolated voluntary movements [e.g. neuromuscular retraining (3)]. In this work we used emotional activation to train facial muscles after peripheral facial nerve palsy, according to the hypothesis that midcingulate area in addition to the primary motor cortex can participate to the motor recovery after facial nerve lesion.
Materials: Tue House-Brackmann scale (HBS) was used to evaluate facial symmetry and synkinesis, both before and after the rehabilitation program.
Methods: Ten patients (36-76 years) suffering a facial nerve lesion (6 Bell's palsy, 2 Ramsay Hunt syndrome, 2 post-surgery palsy) underwent up to 20 physiotherapy sessions. Each session ( 45 minutes long) was led by a physiotherapist. Consecutive sessions were kept at least 3 days apart. The emotional activation of the paretic facial muscles was obtained by asking patients to recall pleasant memories. Patients were guided by the therapist in increasing their awareness of the emotion-evoked movement by concentrating on kinesthesis.
Results: On average, patients started the rehabilitation 80 days after the nerve lesion. At the beginning of the rehabilitation program, patients suffered a moderate facial asymmetry according to the HBS (median HBS score: 3.5; IQR: 3). At the end of the rehabilitation program, HBS score median was reduced to 1 (IQR: 1), indicating a more symmetric face and less severe synkinesis (Wilcoxon test, p = 0.002). Ali patients improved their HBS score.
Discussion: Emotional training, a form of repetitive task-specific training, seems beneficial for people receiving rehabilitation following facial nerve lesion. Tue neural network mediating the emotional training effects could include structures of the limbic system such as the amygdala which are known to project to the facial muscle motoneurons via the midcingulate area (1).
Conclusion: Emotional training of facial muscles led by a physiotherapist is a promising tool for rehabilitation after facial nerve lesions.
References:
1. Morecraft RJ, Louie JL, Herrick JL, Stilwell-Morecraft KS. Cortical
innervation of the facial nucleus in the non-human primate: a new interpretation of the effects of stroke and related subtotal brain trauma on the muscles of facial expression. Brain (2001);124:176-208
2. Gothard KM. Tue amygdalo-motor pathways and the control of facial expressions. Front Neurosci. (2014); 19(8):43
3. Nicastri M, Mancini P, De Seta D, Bertoli G, Prosperini L, Toni D, lnghilleri M, Filipo R. Efficacy of early physical therapy in severe Bell's palsy: a randomized controlled trial. Neurorehabil Neural Repair. (2013);27(6):542-5
