Bioenergetic Evaluation of Muscle Fatigue in Murine Tongue.

Muscle fatigue is the diminution of force required for a particular action over time. Fatigue may be particularly pronounced in aging muscles, including those used for swallowing actions. Because risk for swallowing impairment (dysphagia) increases with aging, the contribution of muscle fatigue to age-related dysphagia is an emerging area of interest. The use of animal models, such as mice and rats (murine models) allows experimental paradigms for studying the relationship between muscle fatigue and swallowing function with a high degree of biological precision that is not possible in human studies. The goal of this article is to review basic experimental approaches to the study of murine tongue muscle fatigue related to dysphagia. Traditionally, murine muscle fatigue has been studied in limb muscles through direct muscle stimulation and behavioral exercise paradigms. As such, physiological and bioenergetic markers of muscle fatigue that have been validated in limb muscles may be applicable in studies of cranial muscle fatigue with appropriate modifications to account for differences in muscle architecture, innervation ratio, and skeletal support. Murine exercise paradigms may be used to elicit acute fatigue in tongue muscles, thereby enabling study of putative muscular adaptations. Using these approaches, hypotheses can be developed and tested in mice and rats to allow for future focused studies in human subjects geared toward developing and optimizing treatments for age-related dysphagia.

Time Heals Most Wounds - Perceptions of Thyroidectomy Scars in Patients With Thyroid Cancer.

BACKGROUND: Patients understandably have concerns about thyroidectomy scars. This study aimed to characterize patients' perceptions of their thyroidectomy scar before and up to 1-y after surgery. METHODS: Patients with papillary thyroid cancer (n = 83) completed semi-structured interviews before and at 2-wks, 6-Wk, 6-mo, and 1-y post-thyroidectomy. Interviews probed about scar concerns and appearance. Content analysis was used to identify themes. RESULTS: The majority of participants did not express concerns about scar appearance. When expressed, preoperative concerns often stemmed from previous surgery experiences or unease with neck incisions. Postoperatively, concerns about scar appearance decreased over time throughout the healing period with most patients being satisfied with their scar appearance by 6-mo after surgery. CONCLUSIONS: Patients with papillary thyroid cancer express few concerns about scar thyroidectomy appearance. Surgeons can reassure patients who have preoperative concerns that most patients are satisfied with their scar appearance by 6-mo after surgery.

Dose in Exercise-Based Dysphagia Therapies: A Scoping Review.

BACKGROUND: Optimal exercise doses for exercise-based approaches to dysphagia treatment are unclear. To address this gap in knowledge, we performed a scoping review to provide a record of doses reported in the literature. A larger goal of this work was to promote detailed consideration of dosing parameters in dysphagia exercise treatments in intervention planning and outcome reporting. METHODS: We searched PubMed, Scopus[Embase], CINAHL, and Cochrane databases from inception to July 2019, with search terms relating to dysphagia and exercises to treat swallowing impairments. Of the eligible 1906 peer-reviewed articles, 72 met inclusionary criteria by reporting, at minimum, both the frequency and duration of their exercise-based treatments. RESULTS: Study interventions included tongue exercise (n = 16), Shaker/head lift (n = 13), respiratory muscle strength training (n = 6), combination exercise programs (n = 20), mandibular movement exercises (n = 7), lip muscle training (n = 5), and other programs that did not fit into the categories described above (n = 5). Frequency recommendations varied greatly by exercise type. Duration recommendations ranged from 4 weeks to 1 year. In articles reporting repetitions (n = 66), the range was 1 to 120 reps/day. In articles reporting intensity (n = 59), descriptions included values for force, movement duration, or descriptive verbal cues, such as "as hard as possible." Outcome measures were highly varied across and within specific exercise types. CONCLUSIONS: We recommend inclusion of at least the frequency, duration, repetition, and intensity components of exercise dose to improve reproducibility, interpretation, and comparison across studies. Further research is required to determine optimal dose ranges for the wide variety of exercise-based dysphagia interventions.

Dysphagia Care Across the Continuum: A Multidisciplinary Dysphagia Research Society Taskforce Report of Service-Delivery During the COVID-19 Global Pandemic.

At the time of writing this paper, there are over 11 million reported cases of COVID-19 worldwide. Health professionals involved in dysphagia care are impacted by the COVID-19 pandemic in their day-to-day practices. Otolaryngologists, gastroenterologists, rehabilitation specialists, and speech-language pathologists are subject to virus exposure due to their proximity to the aerodigestive tract and reliance on aerosol-generating procedures in swallow assessments and interventions. Across the globe, professional societies and specialty associations are issuing recommendations about which procedures to use, when to use them, and how to reduce the risk of COVID-19 transmission during their use. Balancing safety for self, patients, and the public while maintaining adequate evidence-based dysphagia practices has become a significant challenge. This paper provides current evidence on COVID-19 transmission during commonly used dysphagia practices and provides recommendations for protection while conducting these procedures. The paper summarizes current understanding of dysphagia in patients with COVID-19 and draws on evidence for dysphagia interventions that can be provided without in-person consults and close proximity procedures including dysphagia screening and telehealth.

A Randomized Controlled Clinical Trial: No Clear Benefit to Prophylactic Central Neck Dissection in Patients With Clinically Node Negative Papillary Thyroid Cancer.

OBJECTIVE: The aim of this prospective randomized-controlled trial was to evaluate the risks/benefits of prophylactic central neck dissection (pCND) in patients with clinically node negative (cN0) papillary thyroid cancer (PTC). BACKGROUND: Microscopic lymph node involvement in patients with PTC is common, but the optimal management is unclear. METHODS: Sixty patients with cN0 PTC were randomized to a total thyroidectomy (TT) or a TT+ pCND. All patients received postoperative laryngoscopies and standardized radioiodine treatment. Thyroglobulin (Tg) levels and/or neck ultrasounds were performed at 6 weeks, 6 months, and 1 year. RESULTS: Tumors averaged 2.2 ±â€Š0.2 cm and 11.9% had extra-thyroidal extension. Thirty patients underwent a pCND and 27.6% had positive nodes (all ≤6 mm). Rates of postoperative PTH < 10 (33.3% vs 24.1%, P = 0.57) and transient nerve dysfunction (13.3% vs 10.3%, P = 1.00) were not significantly different between groups. Six weeks after surgery, both TT and TT + pCND were equally likely to achieve a Tg < 0.2 (54.5% vs 66.7%, P = 0.54) and/or a stimulated Tg (sTg) <1 (59.3% vs 64.0%, P = 0.78). At 1 year, rates of Tg < 0.2 (88.9% vs 90.0%, P = 1.00) and sTg < 1 (93.8% vs 92.3%, P = 1.00) remained similar between groups. Neck ultrasounds at 1 year were equally likely to be read as normal (85.7% in TT vs 85.1% in pCND, P = 1.00). CONCLUSIONS: cN0 PTC patients treated either with TT or TT + pCND had similar complication rates after surgery. Although microscopic nodes were discovered in 27.6% of pCND patients, oncologic outcomes were comparable at 1 year.

Effects of Tongue Exercise Frequency on Tongue Muscle Biology and Swallowing Physiology in a Rat Model.

Age-related changes in muscle composition and function are often treated using exercise, including muscles of the tongue to treat swallowing impairments (dysphagia). Although tongue exercise is commonly prescribed, optimal tongue exercise doses have not been determined. The purpose of this study was to evaluate effects of varying tongue exercise frequency on tongue force, genioglossus muscle fiber size, composition and metabolism, and swallowing in a rat model. We randomized 41 old and 40 young adult Fischer 344/Brown Norway rats into one of four tongue exercise groups: 5 days/week; 3 days/week; 1 day/week; or sham. Tongue force was higher following all exercise conditions (vs sham); the 5 day/week group had the greatest change in tongue force (p < 0.001). There were no exercise effects on genioglossus (GG) fiber size or MyHC composition (p > 0.05). Significant main effects for age showed a greater proportion of Type I fibers in (p < 0.0001) and increased fiber size of IIa fibers (p = 0.026) in old. There were no significant effects of citrate synthase activity or PGC-1α expression. Significant differences were found in bolus speed and area (size), but findings were potentially influenced by variability. Our findings suggest that tongue force is influenced by exercise frequency; however, these changes were not reflected in characteristics of the GG muscle assayed in this study. Informed by findings of this study, future work in tongue dose optimization will be required to provide better scientific premise for clinical treatments in humans.

A Qualitative Analysis of the Preoperative Needs of Patients With Papillary Thyroid Cancer.

BACKGROUND: Thyroid cancer patients report unmet needs after diagnosis. However, little is known about their specific needs. Therefore, we sought to characterize the needs of patients with thyroid cancer before undergoing surgery. MATERIAL AND METHODS: We conducted semistructured interviews with 32 patients with papillary thyroid cancer after their preoperative surgical consultation. Data were analyzed using thematic content analysis. RESULTS: The central need of patients with thyroid cancer was a strong patient-surgeon relationship characterized by informational and emotional support, and respect for the patient as a person. Patients preferred disease- and treatment-related information to be individualized and to take into account aspects of their daily life. They wanted adequate time for asking questions with thoughtful answers tailored to their case. Patients additionally desired emotional support from the surgeon characterized by empathy and validation of their cancer experience. They particularly wanted surgeons to address their fears and anxiety. Patients also highly valued the surgeons' ability to see beyond their disease and acknowledge them as a unique person with respect to their occupation, psychosocial state, and other individual characteristics. When surgeons met patients' needs, they felt reassured, comfortable with their cancer diagnosis, and prepared for treatment. Suboptimal support increased patients' anxiety particularly when they felt the surgeon minimized their concerns. CONCLUSIONS: Preoperatively, patients with thyroid cancer desire a strong patient-surgeon relationship. They rely on the surgeon to provide adequate informational and emotional support and respect them as individuals. In turn, patients feel reassured and prepared for treatment.

Correlates of Early Pharyngeal High-Resolution Manometry Adoption in Expert Speech-Language Pathologists.

Pharyngeal high-resolution manometry (HRM) is at a point of entry into speech-language pathologist (SLP) clinical practice. However, the demographic characteristics of SLPs who are early adopters of HRM are unclear; perspectives of early adopters may shape how the technology is received by the field at large. We hypothesized that younger SLPs, those working in outpatient settings, those with a strong knowledge base in HRM, and those with experience in other types of instrumentation are more likely to have interest in adopting HRM. We surveyed the population of board-certified SLPs (BCS-S; n = 262) with a 33% response rate (n = 78). Firth logistic regression was used to determine differences in those expressing interest in adopting HRM into future practice (n = 28) and those who did not (n = 45) from the analytic sample of 73 respondents. The best fitting model predicted that SLPs: (1) with training in more types of instrumentation; and (2) believing they could explain the HRM procedure to a patient were more likely to plan to adopt pharyngeal HRM into regular clinical practice. Experience with a variety of instrumentation techniques may encourage SLPs to use new forms of technology. Knowledge of early adopter demographics will allow for development of targeted trainings and determination of HRM implementation barriers. Identification of a clinician sub-group more likely to adopt other new technologies in the future may also be possible.

SLP-Perceived Technical and Patient-Centered Factors Associated with Pharyngeal High-Resolution Manometry.

High-resolution manometry (HRM) objectively measures swallowing-related pressures in the pharynx and esophagus. It has been used in many research applications, but it is unclear how HRM is perceived amongst speech-language pathologists (SLP) as it enters into clinical practice. The purpose of this study was to explore SLP perceptions of clinical HRM use. Based on qualitative data collected at four focus groups held at two national conferences and a survey based on open-ended questions, we found broad consensus among those queried regarding how HRM's objective and targeted data could enhance diagnosis and drive treatments. However, we found less consensus among SLPs regarding which patients may and may not benefit, as well as when in the clinical process HRM would best supplement existing technologies, showing a need for further research. These findings highlight how SLPs can be motivated to adopt new clinical technologies if they see a patient-centered benefit and underscore the need for continued SLP education on pharyngeal HRM.

Age-related effect of cell death on fiber morphology and number in tongue muscle.

INTRODUCTION: Multiple pathways may exist for age-related tongue muscle degeneration. Cell death is one mechanism contributing to muscle atrophy and decreased function. We hypothesized with aging, apoptosis, and apoptotic regulators would be increased, and muscle fiber size and number would be reduced in extrinsic tongue muscles. METHODS: Cell death indices, expression of caspase-3 and Bcl-2, and measures of muscle morphology and number were determined in extrinsic tongue muscles of young and old rats. RESULTS: Significant increases in cell death, caspase-3, and Bcl-2 were observed in all extrinsic tongue muscles along with reductions in muscle fiber number in old rats. DISCUSSION: We demonstrated that apoptosis indices increase with age in lingual muscles and that alterations in apoptotic regulators may be associated with age-related degeneration in muscle fiber size and number. These observed apoptotic processes may be detrimental to muscle function, and may contribute to degradation of cranial functions with age. Muscle Nerve 57: E29-E37, 2018.

Effect of neuromuscular electrical stimulation frequency on muscles of the tongue.

INTRODUCTION: Neuromuscular electrical stimulation (NMES) for the treatment of swallowing disorders is delivered at a variety of stimulation frequencies. We examined the effects of stimulation frequency on tongue muscle plasticity in an aging rat model. METHODS: Eighty-six young, middle-aged, and old rats were assigned to either bilateral hypoglossal nerve stimulation at 10 or 100 Hz (5 days/week, 8 weeks), sham, or no-implantation conditions. Muscle contractile properties and myosin heavy chain (MyHC) composition were determined for hyoglossus (HG) and styloglossus (SG) muscles. RESULTS: Eight weeks of 100-Hz stimulation resulted in the greatest changes in muscle contractile function with significantly longer contraction and half-decay times, the greatest reduction in fatigue, and a transition toward slowly contracting, fatigue-resistant MyHC isoforms. DISCUSSION: NMES at 100-Hz induced considerable changes in contractile and phenotypic profiles of HG and SG muscles, suggesting higher frequency NMES may yield a greater therapeutic effect. Muscle Nerve, 2018.

A Pilot Study of Perceived Mouth Dryness, Perceived Swallowing Effort, and Saliva Substitute Effects in Healthy Adults Across the Age Range.

Xerostomia, or perceived mouth dryness, increases with advancing age, but its influence on swallowing effort is unknown. This study: (1) quantified relationships among age, perceived sense of swallowing effort, and ratings of perceived mouth dryness, and (2) examined changes in swallowing effort following application of a gel-based saliva substitute in healthy participants. This was a cross-sectional observational study and data were collected from attendees of a community healthy aging fair. Forty-two healthy participants (mean age = 65 years; 20 female) were enrolled. Each participant rated perceived effort with swallowing and perceived mouth dryness on a 10-cm horizontal, undifferentiated line. After participants applied a gel-based saliva substitute (Biotene® Oral Balance) to their tongue and oral mucosa, they rated perceived effort with swallowing again. Age was associated with greater perceived mouth dryness (r = 0.37, p < 0.03) but not with perceived swallowing effort (r = 0.16, p = 0.32). Perceived mouth dryness was associated with greater perceived swallowing effort (r = 0.62, p < 0.001). Perceived swallowing effort declined following application of the salivary substitute (mean difference = 9.39 mm, p < 0.002). Age was found to be a significant predictor of perceived mouth dryness (p < .02); and perceived mouth dryness was found to significantly predict perceived swallow effort (p < .001). Perceived mouth dryness increased with advancing age, but perceived swallowing effort did not. Regardless of age, participants with higher levels of perceived mouth dryness also reported more perceived effort with swallowing suggesting a role for adequate oral lubrication in this perception. Even in healthy participants, use of a gel-based saliva substitute lowered perceived swallowing effort.

Patient Adherence to Dysphagia Recommendations: A Systematic Review.

Patient adherence to treatment recommendations is an important issue for healthcare providers, in a multitude of specialties, and is critical when assessing the efficacy and effectiveness of a particular treatment approach. Patients who have swallowing impairment often require complex and specific interventions requiring altered daily patterns of behavior. Patients with dysphagia who do not follow recommendations or prescribed exercises may not receive maximum benefit of an intervention. Poor adherence also makes it more difficult to evaluate efficacy of a treatment both clinically and in experimental settings. Further, swallow safety can be compromised if certain recommendations are not followed. Our purpose was to systematically review the literature to understand what is known about adherence within the field of dysphagia treatment. We systematically identified 12 studies that tracked and reported patient-specific adherence. In this review, we found that the average adherence rate from these studies ranges between 21.9 and 51.9%. Adherence to prophylactic treatment recommendations for patients with head and neck cancer was the focus in 9/12 studies. The findings of this review identify a large gap in knowledge regarding adherence to dysphagia treatment. Few studies account for adherence within their study designs. When planning dysphagia treatment studies, it is imperative that investigators include information regarding patient adherence to accurately interpret findings. Given the variable adherence rates found in this review, factors influencing patient adherence with dysphagia treatments should be identified to increase adherence in future trials.

Correction to: Patient Adherence to Dysphagia Recommendations: A Systematic Review.

The original version of this article unfortunately contains mistakes. The second sentence in the section "Results", under the heading "Study Design" was incorrect. It should read as: Two studies [24, 29] used a prospective cohort study design with a JAMA rating of 2. Four studies [17, 25, 27, 34] completed retrospective studies earning a JAMA score of 3. Four studies [26, 28, 30, 33] earned a JAMA quality rating score of 4 and used the following designs: case series [26, 28, 33], and pilot study [30]. In Table 1, "Study Population (n)" and "Design (JAMA quality rating)" values were incorrect for Shinn et al. (2013) [24]. The correct information is given here. HNC (n = 109) Prospective Cohort (2).

Alterations of intrinsic tongue muscle properties with aging.

INTRODUCTION: Age-related decline in the intrinsic lingual musculature could contribute to swallowing disorders, yet the effects of age on these muscles is unknown. We hypothesized there is reduced muscle fiber size and shifts to slower myosin heavy chain (MyHC) fiber types with age. METHODS: Intrinsic lingual muscles were sampled from 8 young adult (9 months) and 8 old (32 months) Fischer 344/Brown Norway rats. Fiber size and MyHC were determined by fluorescent immunohistochemistry. RESULTS: Age was associated with a reduced number of rapidly contracting muscle fibers, and more slowly contracting fibers. Decreased fiber size was found only in the transverse and verticalis muscles. DISCUSSION: Shifts in muscle composition from faster to slower MyHC fiber types may contribute to age-related changes in swallowing duration. Decreasing muscle fiber size in the protrusive transverse and verticalis muscles may contribute to reductions in maximum isometric tongue pressure found with age. Differences among regions and muscles may be associated with different functional demands. Muscle Nerve 56: E119-E125, 2017.

Effects of Change in Tongue Pressure and Salivary Flow Rate on Swallow Efficiency Following Chemoradiation Treatment for Head and Neck Cancer.

Patients treated with chemoradiation for head and neck cancer frequently develop dysphagia. Tissue damage to the oral tongue causing weakness along with decreases in saliva production may contribute to dysphagia. Yet, effects of these variables on swallowing-related measures are unclear. The purpose of this study was (1) to determine effects of chemoradiation on tongue pressures, as a surrogate for strength, and salivary flow rates and (2) to elucidate relationships among tongue pressures, saliva production, and swallowing efficiency by bolus type. Twenty-one patients with head and neck cancer treated with chemoradiation were assessed before and after treatment and matched with 21 healthy control participants who did not receive chemoradiation. Each participant was given a questionnaire to rate dysphagia symptoms. Videofluoroscopic Evaluation of Swallowing (VFES) was used to determine swallowing efficiency; the Saxon test measured salivary flow rate; and the Iowa Oral Performance Instrument (IOPI) was used for oral tongue maximum and endurance measures. Results revealed significantly lower tongue endurance measures for patients post-treatment as compared to controls (p = .012). Salivary flow rates also were lower compared to pre-treatment (p = .000) and controls (p = .000). Simple linear regression analyses showed that change in salivary flow rate was predictive of change in swallow efficiency measures from pre- to post-treatment for 1 mL thin liquid (p = .017), 3 mL nectar-thick liquid (p = .026), and 3 mL standard barium pudding (p = .011) boluses. Based on these findings, it appears that chemoradiation treatment affects tongue endurance and salivary flow rate, and these changes may impact swallow efficiency. These factors should be considered when planning treatment for dysphagia.

Differential impact of unilateral stroke on the bihemispheric motor cortex representation of the jaw and tongue muscles in young and aged rats.

Introduction: Dysphagia commonly occurs after stroke, yet the mechanisms of post-stroke corticobulbar plasticity are not well understood. While cortical activity associated with swallowing actions is bihemispheric, prior research has suggested that plasticity of the intact cortex may drive recovery of swallowing after unilateral stroke. Age may be an important factor as it is an independent predictor of dysphagia after stroke and neuroplasticity may be reduced with age. Based on previous clinical studies, we hypothesized that cranial muscle activating volumes may be expanded in the intact hemisphere and would contribute to swallowing function. We also hypothesized that older age would be associated with limited map expansion and reduced function. As such, our goal was to determine the impact of stroke and age on corticobulbar plasticity by examining the jaw and tongue muscle activating volumes within the bilateral sensorimotor cortices. Methods: Using the middle cerebral artery occlusion rat stroke model, intracortical microstimulation (ICMS) was used to map regions of sensorimotor cortex that activate tongue and jaw muscles in both hemispheres. Young adult (7 months) and aged (30 months) male F344 × BN rats underwent a stroke or sham-control surgery, followed by ICMS mapping 8 weeks later. Videofluoroscopy was used to assess oral-motor functions. Results: Increased activating volume of the sensorimotor cortex within the intact hemisphere was found only for jaw muscles, whereas significant stroke-related differences in tongue activating cortical volume were limited to the infarcted hemisphere. These stroke-related differences were correlated with infarct size, such that larger infarcts were associated with increased jaw representation in the intact hemisphere and decreased tongue representation in the infarcted hemisphere. We found that both age and stroke were independently associated with swallowing differences, weight loss, and increased corticomotor thresholds. Laterality of tongue and jaw representations in the sham-control group revealed variability between individuals and between muscles within individuals. Conclusion: Our findings suggest the role of the intact and infarcted hemispheres in the recovery of oral motor function may differ between the tongue and jaw muscles, which may have important implications for rehabilitation, especially hemisphere-specific neuromodulatory approaches. This study addressed the natural course of recovery after stroke; future work should expand to focus on rehabilitation.

Altered tongue muscle contractile properties coincide with altered swallow function in the adult Ts65Dn mouse model of down syndrome.

Purpose: Down syndrome (DS) is a developmental disability associated with difficulties in deglutition. The adult Ts65Dn mouse model of DS has been previously shown to have differences in measures of swallowing compared with euploid controls. However, the putative mechanisms of these differences in swallowing function are unclear. This study tested the hypothesis that the Ts65Dn genotype is associated with atypical measures of tongue muscle contractile properties, coinciding with atypical swallow function. Methods: Adult (5-month-old) Ts65Dn (n = 15 female, 14 male) and euploid sibling controls (n = 16 female, 14 male) were evaluated through videofluoroscopy swallow studies (VFSS) to quantify measures of swallowing performance including swallow rate and inter-swallow interval (ISI). After VFSS, retrusive tongue muscle contractile properties, including measures of muscle fatigue, were determined using bilateral hypoglossal nerve stimulation. Results: The Ts65Dn group had significantly slower swallow rates, significantly greater ISI times, significantly slower rates of tongue force development, and significantly greater levels of tongue muscle fatigue, with lower retrusive tongue forces than controls in fatigue conditions. Conclusion: Tongue muscle contractile properties are altered in adult Ts65Dn and coincide with altered swallow function.

Tongue and laryngeal exercises improve tongue strength and vocal function outcomes in a Pink1-/- rat model of early Parkinson disease.

Parkinson disease (PD) causes voice and swallow dysfunction even in early stages of the disease. Treatment of this dysfunction is limited, and the neuropathology underlying this dysfunction is poorly defined. Targeted exercise provides the greatest benefit for offsetting voice and swallow dysfunction, and previous data suggest the hypoglossal nucleus and noradrenergic-locus coeruleus (LC) may be involved in its early pathology. To investigate relationships between targeted exercise and neuropathology of voice and swallow dysfunction, we implemented a combined exercise paradigm that included tongue force and vocalization exercises early in the Pink1-/- rat model. We tested the hypotheses that (1) tongue and vocal exercise improves tongue force and timing behaviors and vocalization outcomes, and (2) exercise increases optical density of serotonin (5-HT) in the hypoglossal nucleus, and tyrosine hydroxylase immunoreactive (Th-ir) cell counts in the LC. At two months of age Pink1-/- rats were randomized to exercise or non-exercise treatment. Age-matched wildtype (WT) control rats were assigned to non-exercise treatment. Tongue force and timing behaviors and ultrasonic vocalizations were measured at baseline (two months) and final (four months) timepoints. Optical density of 5-HT in the hypoglossal nucleus and TH-ir cell counts in the LC were obtained. Pink1-/- rats produced greater tongue forces, faster tongue contraction, and higher-intensity vocalization following exercise. There were no differences in LC TH-ir. The non-exercised Pink1-/- group had reduced density of 5-HT in the hypoglossal nucleus compared to the WT control group. The changes to tongue function and vocalization after targeted exercise suggests exercise intervention may be beneficial in early PD.

Tongue muscle plasticity following hypoglossal nerve stimulation in aged rats.

INTRODUCTION: Age-related decreases in tongue muscle mass and strength have been reported. It may be possible to prevent age-related tongue muscle changes using neuromuscular electrical stimulation (NMES). Our hypothesis was that alterations in muscle contractile properties and myosin heavy chain composition would be found after NMES. METHODS: Fifty-four young, middle-aged, and old 344/Brown Norway rats were included in this study. Twenty-four rats underwent bilateral electrical stimulation of the hypoglossal nerves for 8 weeks and were compared with control or sham rats. Muscle contractile properties and myosin heavy chain (MHC) in the genioglossus (GG), styloglossus (SG), and hyoglossus (HG) muscles were examined. RESULTS: Compared with unstimulated control rats, we found reduced muscle fatigue, increased contraction and half-decay times, and increased twitch and tetanic tension. Increased type I MHC was found, except for in GG in old and middle-aged rats. CONCLUSION: Transitions in tongue muscle contractile properties and phenotype were found after NMES.