Neuromotor Speech Recovery Across Different Behavioral Speech Modifications in Individuals Following Facial Transplantation.

Marziye Eshghi,Brian Richburg,Jordan R Green,Bohdan Pomahac,Hayden M Ventresca,Bridget J Perry

doi:10.3389/fneur.2020.593153

Abstract

Despite signs of facial nerve recovery within a few months following face transplantation, speech deficits persist for years. Behavioral speech modifications (e.g., slower-than-normal speaking rate and increased loudness) have shown promising potential to enhance speech intelligibility in populations with dysarthric speech. However, such evidence-based practice approach is lacking in clinical management of speech in individuals with facial transplantation. Because facial transplantation involves complex craniofacial reconstruction and facial nerve coaptation, it is unknown to what extent individuals with face transplant are capable of adapting their motor system to task-specific articulatory demands. The purpose of this study was to identify the underlying articulatory mechanisms employed by individuals with face transplantation in response to speech modification cues at early and late stages of neuromotor recovery. In addition, we aimed to identify speech modifications that conferred improved speech clarity. Participants were seven individuals who underwent full or partial facial vascularized composite allografts that included lips and muscles of facial animation and were in early (~2 months) or late (~42 months) stages of recovery. Participants produced repetitions of the sentence “Buy Bobby a puppy” in normal, fast, loud, and slow speech modifications. Articulatory movement traces were recorded using a 3D optical motion capture system. Kinematic measures of average speed (mm/s) and range of movement (mm3) were extracted from the lower lip (± jaw) marker. Two speech language pathologists rated speech clarity for each speaker using a visual analog scale (VAS) approach. Results demonstrated that facial motor capacity increased from early to late stages of recovery. While individuals in the early group exhibited restricted capabilities to adjust their motor system based on the articulatory demands of each speech modification, individuals in the late group demonstrated faster speed and larger-than-normal range of movement for loud speech, and slower speed and larger-than-normal range of movement for slow speech. In addition, subjects in both groups showed overreliance on jaw rather than lip articulatory function across all speech modifications, perhaps as a compensatory strategy to optimize articulatory stability and maximize speech function. Finally, improved speech clarity was associated with loud speech in both stages of recovery.

Highlights

With over 40 facial transplantation surgeries completed worldwide, this procedure is considered an effective reconstructive option for restoring a patient’s facial appearance and oromotor functions after a traumatic injury
Results from our study suggest that [1] motor adaptation to articulatory demands of speech modifications increased from 2 to 42 months post-surgery as an indication of neural recovery; [2] across the four speech modifications, loud speech modification most consistently improved speech clarity during early and late stages of neuromotor recovery; and [3] individuals in early and late stages of neuromotor recovery over-rely on jaw for the lip articulatory function across all speech modifications
Our findings suggest that the articulatory kinematic adaptations to speech modifications are significantly restricted in individuals at the early stage of neuromotor recovery post facial transplant surgery but improve over time

Summary

Introduction

With over 40 facial transplantation surgeries completed worldwide, this procedure is considered an effective reconstructive option for restoring a patient’s facial appearance and oromotor functions after a traumatic injury. De Letter and colleges [2] reported that facial motor function improved over 38 months post-surgery as indicated by gains in lip motor function scores and increased muscle activation levels based on electromyography (EMG) during a speech task (i.e., a sentence completion task). In addition to these longitudinal studies, a case study conducted by Grigos et al [7] reported increases in vertical jaw and lip movements during speech and non-speech (e.g., lip opening, closure, retraction, and protrusion) tasks over 13 months post-transplant. The same study reported several negative findings such that the same gains were not seen for lip spreading, and jaw and lip movement variability were greater than the controls, which may in part explain continued mild functional speech impairments in this population

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