A wide variety of treatments have been developed to improve respiratory function and quality of life in patients with bilateral vocal fold paresis (BVFP). One experimental method is the electrical activation of the posterior cricoarytenoid (PCA) muscle with a laryngeal pacemaker (LP) to open the vocal folds. We used an ovine (sheep) model of unilateral VFP to study the long-term effects of functional electrical stimulation on the PCA muscles. The left recurrent laryngeal nerve was cryo-damaged in all animals and an LP was implanted except for the controls. After a reinnervation phase of six months, animals were pooled into groups that received either no treatment, implantation of an LP only, or implantation of an LP and six months of stimulation with different duty cycles. Automated image analysis of fluorescently stained PCA cross-sections was performed to assess relevant muscle characteristics. We observed a fast-to-slow fibre type shift in response to nerve damage and stimulation, but no complete conversion to a slow-twitch-muscle. Fibre size, proportion of hybrid fibres, and intramuscular collagen content were not substantially altered by the stimulation. These results demonstrate that 30 Hz burst stimulation with duty cycles of 40% and 70% did not induce PCA atrophy or fibrosis. Thus, long-term stimulation with an LP is a promising approach for treating BVFP in humans without compromising muscle conditions.

Functional Electrical Stimulation (FES) is an established intervention for a range of muscular and neurological disorders that has already been studied in numerous publications. However, its application to Peripheral Facial nerve Paralysis (PFP) still needs to be sufficiently investigated. As the first approach known to the authors, this study examines the effect of FES on the facial muscles in complete PFP using ultrasonography as a means of observation. In a prospective single-center observational pilot study, ten patients with complete PFP, confirmed by needle-electromyography (EMG), performed FES of the affected lateral mouth region at home twice daily for 20 minutes. The facial muscles’ Cross-Sectional Area (CSA) was regularly assessed using sonographic quantification. While the CSA of most non-stimulated muscles decreased considerably during ongoing paralysis, a significant CSA increase of the Zygomaticus Muscle (ZYG), which was regularly subjected to FES, could be demonstrated. FES can halt the atrophy of denervated ZYG and potentially other facial muscles. Further investigations with a more significant patient collective are recommended. From now on, FES could be established as an additive method in the non-invasive treatment of PFP.

Surface Functional Electrical Stimulation (FES) is a well-studied intervention for multiple muscular disorders. However, it is still controversially discussed as a complementary therapy for complete facial paralysis. The aim of this intervention is to test a daily home-based ES concept as a pilot study regarding safety, feasibility, and effects on facial functionality and symmetry. In a prospective single-centre pilot study, 10 patients (median 61 years, denervation 130 d) with complete peripheral facial paralysis performed home-based FES of the affected lateral mouth region Stimulation parameters, facial paralysis scores and standardised photographs were assessed in monthly follow-ups. No serious adverse events appeared. Stimulation parameters could be constantly increased indicating effective muscle training while subjectively perceived functionality of the face improved. Thus, smile angle of the paralysed side improved as well. FES is a safe therapy model for application in facial nerve paralysis patients. A feasible stimulation protocol could be applied, which improved the functionality and symmetry of the stimulated facial region. A future controlled, randomised and double-blind follow-up study is needed to investigate these initial results in a further evolved replicable setting.

Quantitative imaging in life sciences has evolved into a powerful approach combining advanced microscopy acquisition and automated analysis of image data. The focus of the present study is on the imaging-based evaluation of the posterior cricoarytenoid muscle (PCA) influenced by long-term functional electrical stimulation (FES), which may assist the inspiration of patients with bilateral vocal fold paresis. To this end, muscle cross-sections of the PCA of sheep were examined by quantitative image analysis. Previous investigations of the muscle fibers and the collagen amount have not revealed signs of atrophy and fibrosis due to FES by a laryngeal pacemaker. It was therefore hypothesized that regardless of the stimulation parameters the fat in the muscle cross-sections would not be significantly altered. We here extending our previous investigations using quantitative imaging of intramuscular fat in cross-sections. In order to perform this analysis both reliably and faster than a qualitative evaluation and time-consuming manual annotation, the selection of the automated method was of crucial importance. To this end, our recently established deep neural network IMFSegNet, which provides more accurate results compared to standard machine learning approaches, was applied to more than 300 H&E stained muscle cross-sections from 22 sheep. It was found that there were no significant differences in the amount of intramuscular fat between the PCA with and without long-term FES, nor were any significant differences found between the low and high duty cycle stimulated groups. This study on a human-like animal model not only confirms the hypothesis that FES with the selected parameters has no negative impact on the PCA, but also demonstrates that objective and automated deep learning-based quantitative imaging is a powerful tool for such a challenging analysis.

Objective fitting measures offer a means to circumvent the subjectivity of cochlear implant programming, with the stapedius reflex representing one robust predictor of the maximum comfortable loudness level. With the present study, it was investigated whether long-term electromyographic measurements of the stapedius muscle using implanted electrodes are feasible. In nine sheep, myoelectrical activities were recorded intraoperatively and synchronized with middle ear admittance as a reference signal. For acoustic stimulation pure tones with different frequencies were used. The electrodes were placed at the stapedius muscle surface after exposing it via the retrofacial approach. EMG-based detection of the stapedius reflex was achievable over six months when electrode integrity and placement were preserved. The treated muscles were subsequently excised, cut and examined histologically. No signs of atrophy were found in the muscles examined. However, the histological section series showed a clear division of the muscle from proximal to distal, the ratio between tendon and muscle fibers being most pronounced in favor of the muscle fibers in the proximal section. The integration of an electromyography-based measurement method for the objective determination of the stapedius reflex threshold and thus, for the long-term adjustment of cochlear implants, appears possible and could potentially enable autonomous fitting of implants.

To understand how small animals cope with complex, unstructured, and unpredictable substrates, we analyzed the kinetics of rats (n = 10) moving at a fast and at a moderate trot over an unperturbed substrate and a substrate subjected to active horizontal perturbations. Perturbations were active single forwards or backwards displacements of an instrumented platform by amplitudes of 5mm or 10mm in 0.05s. Single leg ground reaction forces (SLGRF) were collected for unperturbed and perturbed locomotion (hindlimbs: 50/102, forelimbs: 45/130, respectively). When negotiating horizontal perturbations, rats displayed gait resetting (braking, accelerating) and non-resetting behaviors. Feedforward strategies differed between the fore- and hindlimbs. In circa 60% of the perturbed trials, forelimbs started the step in acceleration mode, while hindlimbs began the stance mostly in non-resetting mode (∼45%). In about 50% of all perturbed steps, the impulse provided by the SLGRF displayed a change in behavior according to the expected response to the perturbation. The remaining 50% retained the feedforward strategy. Still, most perturbed trials displayed changes in SLGRF patterns that indicated passive and active reactions to platform shifts. Our results indicate that rats’ sensorimotor control system tunes fore- and hindlimbs differently in expectation of a perturbation. In addition, the tendon-muscle systems of the limbs are recruited to prevent leg collapse at the beginning and end of the stance. At lower speeds, spinal and/or higher center commands have enough time to re-adapt limb behavior. At higher speeds of locomotion, rats rely more on their limbs’ intrinsic stability and on feedforward control.