A New Neurorehabilitative Postsurgery Intervention for Facial Palsy Based on Smile Observation and Hand-Mouth Motor Synergies

Abstract

Objective: To perform a preliminary test of a new rehabilitation treatment (FIT-SAT), based on mirror mechanisms, for gracile muscles after smile surgery.

Method: A pre- and postsurgery longitudinal design was adopted to study the efficacy of FIT-SAT. Four patients with bilateral facial nerve paralysis (Moebius syndrome) were included. They underwent two surgeries with free muscle transfers, one year apart from each other. The side of the face first operated on was rehabilitated with the traditional treatment, while the second side was rehabilitated with FIT-SAT. The FIT-SAT treatment includes video clips of an actor performing a unilateral or a bilateral smile to be imitated (FIT condition). In addition to this, while smiling, the participants close their hand in order to exploit the overlapped cortical motor representation of the hand and the mouth, which may facilitate the synergistic activity of the two effectors during the early phases of recruitment of the transplanted muscles (SAT). The treatment was also aimed at avoiding undesired movements such as teeth grinding. Discussion. Results support FIT-SAT as a viable alternative for smile rehabilitation after free muscle transfer. We propose that the treatment potentiates the effect of smile observation by activating the same neural structures responsible for the execution of the smile and therefore by facilitating its production. Closing of the hand induces cortical recruitment of hand motor neurons, recruiting the transplanted muscles, and reducing the risk of associating other unwanted movements such as teeth clenching to the smile movements.

Figure 1

Modified from Ferrari et al. [21]: FIT-SAT theoretical assumptions. (a) FIT combined action observation with the direct effects of action execution suggesting that activation of motor areas by action observation becomes reinforced by the concomitant active execution of the observed actions¹⁹; (b) the synergistic activity of hand closing while smiling should facilitate the activation of the cortical areas connected to the mouth. We hypothesized that hand contraction would facilitate the recruitment of the gracilis muscle as a consequence of the activity of mouth motor neurons in motor cortical areas.

Figure 2

FIT-SAT treatment. (a) The FIT-SAT treatment was performed at home for about 6 months. After the first surgery, the right side of the face was rehabilitated by teeth clenching and mirror feedback. After the second surgery, the FIT-SAT treatment started as soon as the patient began to recruit the muscle. (b) The FIT-SAT treatment was divided into two phases: in the first (unilateral) phase, patients performed unilateral exercises in order to recruit the left transplanted muscle as soon as possible. The second (bilateral) phase started only after the patient was able to perform multiple repetitions of the unilateral left movement maintaining the posture for at least three seconds. From now on, the patient had to learn to coordinate the two sides of the face performing bilateral exercises. (c) Experimental condition: (1) no smile observation and no-hand contraction (baseline condition, BC), (2) no smile observation but hand contraction (HC), (3) smile observation but no-hand contraction (SO), and (4) smile observation and hand contraction (SO-HC).

Figure 3

Kinematic parameters. (a) Example of one trial. The black line represents the excursion of the markers placed on the participant's mouth. The movement began after the participants observed the actress's smile and maintained the posture for about three seconds. The baseline is shown in gray. In this phase, the subject did not perform any movement. (b) Three reflective passive markers were placed on the participant's face (left mouth marker, LMM; right mouth marker, RMM; and reference marker, RM). Bilateral smile amplitude was calculated as the maximum Euclidian distance (MMA) in millimeters between the two lip corner markers (LMM and RMM). This measure was expressed as a percentage of the MMA at baseline (%MMA). Similarly, left/right side parameters were calculated as the Euclidian distances in millimeters between LMM or RMM lip corner marker and the nose marker (RM). Left/right side parameters were expressed as the percentage of side baseline (left or right, respectively, before movement onset).

Figure 4

Results of unilateral task at T1. Left %MMA was the Euclidian distance in millimeters between the two lip corner markers expressed as a percentage of the MMA at baseline. All the experimental conditions are represented: smile observation followed by imitation of the same smile movement and ipsilateral hand contraction (SO-HC), smile observation followed by imitation of the same smile movement but without hand contraction (SO), no smile observation but hand contraction (HC), and no smile observation and no hand contraction (BC). Error bars represent SE (standard errors of the means).

Figure 5

The graphs show the results of the bilateral analysis between the first (T1) and the last acquisition (T2). The parameters considered were (a) %MMA (the maximum Euclidian distance in millimeters between the two lip corner markers), (b) %AI (asymmetry index), (c) % left side (the Euclidian distances in millimeters between the left lip corner marker and the nose marker), and (d) right side (the Euclidian distances in millimeters between the right lip corner marker and the nose marker). Error bars represent SE (standard errors of the means).

Figure 6

The graph shows the results of the bilateral task in both acquisitions considering the FIT-SAT conditions. Specifically, %MMA (the maximum Euclidian distance in millimeters between the two lip corner markers) increased in SO-HC (smile observation and hand contraction) with respect to the baseline (BC). Error bars represent SE (standard errors of the means).

Figure 7

The graph shows the results between the % right side and the % left side (the Euclidian distances in millimeters between the left/right lip corner marker and the nose marker, Figure 3(b)) at the first acquisition (T1, blue) and at the last acquisition (T2, orange), respectively. Error bars represent SE (standard errors of the means).