The Feasibility of Home-Based Treatment Using Vibratory Stimulation in Chronic Severe Dysphagia.

PURPOSE: Previously, externally placed vibratory laryngeal stimulation increased rates of swallowing in persons with and without dysphagia. This study examined the feasibility of using a vibratory device on the skin over the thyroid cartilage for home-based swallowing rehabilitation in long-standing dysphagia. METHOD: Only participants with long-standing dysphagia (> 6 months) following cerebrovascular accident or head/neck cancer who had not previously benefited from dysphagia therapy participated. The device had two modes used daily for 90 days. In automatic mode, participants wore the device when awake, which vibrated for 4-8 s every 5 min to trigger a volitional swallow. In manual mode, participants practiced by activating vibration while swallowing rapidly. Study-related adverse events, such as pneumonia, and device-recorded adherence were tracked. Swallowing function on a modified barium swallow study was assessed at baseline and after 3 months of device use. Outcome measures included the Dysphagia Outcome and Severity Scale (DOSS), Penetration-Aspiration Scale (PAS), and swallowing timing measures. Participants' perceptions of the vibratory device and training were obtained. RESULTS: The intent to treat analysis showed seven of 11 participants completed the study, all with severe chronic dysphagia. Of those seven participants completing the study, two developed respiratory complications (possibly due to pneumonia) that cleared after antibiotic intervention. For prescribed practice trials, adherence was 80% or greater in four of seven participants (57%) whereas prescribed automatic stimulations were met in only two of seven participants (29%). Three participants (43%) had a modest benefit on DOSS. The time to vestibule closure after the bolus passed the ramus was reduced in five participants (71%) on the modified barium swallow study. CONCLUSION: Overall, the results have indicated that intensive home-based practice with stimulation may provide limited functional benefits in severe chronic dysphagia. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21498591.

Healthy Volunteers Immediately Adapt to Submental Stimulation During Swallowing.

OBJECTIVES: Transcutaneous stimulation above and below the hyoid is used to assist patients with swallowing disorders (dysphagia) but has shown different effects. Previously, infrahyoid transcutaneous stimulation lowered the hyoid and larynx resisting swallowing movement while suprahyoid stimulation had no effects on hyolaryngeal movement either at rest or during swallowing. More recently, large submental electrodes, covering the submental region, are used for swallowing therapy in combination with resistance therapy. To gain insight into the effects of these electrodes on movement during swallowing, we studied healthy volunteers using videofluoroscopy (VF). We hypothesized that submental electrical stimulation might elevate the hyoid but not the larynx increasing vestibular opening potentially reducing swallowing safety. MATERIALS AND METHODS: While undergoing VF, seven healthy volunteers (mean age 51, 5 males) swallowed 5 mL of liquid barium on at least ten trials randomly ordered across three conditions: stimulation at rest, swallowing without stimulation, and swallowing with stimulation. RESULTS: During stimulation at rest, significant (one tailed p < 0.05) anterior movement occurred in the hyoid and larynx, no superior hyoid and laryngeal movement and an increase in the distance between the hyoid and larynx. When comparing swallowing with and without submental stimulation, during stimulation volunteers significantly reduced anterior hyoid motion (p = 0.028) and increased hyoid elevation (p = 0.043) without changing anterior or superior laryngeal movement or the distance between the hyoid and larynx. CONCLUSIONS: The healthy volunteers immediately corrected for the effects of submental stimulation by reducing hyoid anterior motion and increasing superior hyoid motion without changing laryngeal motion to prevent increased vestibule opening with stimulation. This suggests that healthy volunteers had an internal schema for swallowing movement patterning with feedforward correction for the effects of stimulation.

An Exploration of Lung Volume Effects on Swallowing in Chronic Obstructive Pulmonary Disease.

Purpose Chronic obstructive pulmonary disease (COPD) limits respiration, which may negatively impact airway safety during swallowing. It is unknown how differences in lung volume in COPD may alter swallowing physiology. This exploratory study aimed to determine how changes in lung volume impact swallow duration and coordination in persons with stable state COPD compared with older healthy volunteers (OHVs). Method Volunteers ≥ 45 years with COPD (VwCOPDs; n = 9) and OHVs (n = 10) were prospectively recruited. Group and within-participant differences were examined when swallowing at different respiratory volumes: resting expiratory level (REL), tidal volume (TV), and total lung capacity (TLC). Participants swallowed self-administered 20-ml water boluses by medicine cup. Noncued (NC) water swallows were followed by randomly ordered block swallowing trials at three lung volumes. Estimated lung volume (ELV) and respiratory-swallow patterning were quantified using spirometry and respiratory inductive plethysmography. Manometry measured pharyngeal swallow duration from onset of base of tongue pressure increase to offset of negative pressure in the pharyngoesophageal segment. Results During NC swallows, the VwCOPDs swallowed at lower lung volumes than OHVs (p = .011) and VwCOPDs tended to inspire after swallows more often than OHVs. Pharyngeal swallow duration did not differ between groups; however, swallow duration significantly decreased as the ELV increased in VwCOPDs (p = .003). During ELV manipulation, the COPD group inspired after swallowing more frequently at REL than at TLC (p = .001) and at TV (p = .002). In conclusion, increasing respiratory lung volume in COPD should improve safety by reducing the frequency of inspiration after a swallow.

Acoustic and Aerodynamic Comparisons of Voice Qualities Produced After Voice Training.

Characteristics of true vocal fold vibration such as the proportion of closed phase of vibration to open phase, longitudinal tension, and the amount of medial compression are used to define four conditions during Estill Voice Training. However, it is unknown whether trainees achieve these phonatory differences after training. Acoustic and aerodynamic measures were used to determine differences in Slack, Thick, Thin, and Stiff conditions. Twenty-four female speech-language pathology graduate students received training perceiving and producing these four conditions and volunteered to participate 3-5 months later. After a 20-minute refresher training, participants were recorded using the Phonatory Aerodynamic System with electroglottography and Computerized Speech Lab. Four Estill Voice Training experts independently categorized the voice quality productions. Aerodynamic and acoustic measures of productions classified by at least three of four experts as having the intended quality determined if measures differentiated among voice qualities and supported the hypothesized physiological concepts used in training at Bonferroni corrected P ≤ 0.0063. Results showed that Slack had low fundamental frequency (fo), low sound pressure level (SPL), and high vibratory instability; Thick had high subglottal pressure (Psg), high SPL, and high vibratory stability; Stiff had high airflow while Thin had lower Psg than Thick. Seven measures differentiated the four qualities with 88.1% accuracy while only Psg, airflow, and jitter were required to differentiate Thick, Stiff, and Thin with 88.7% accuracy. As acoustic and aerodynamic measures differentiated among voice qualities and supported the theoretical physiological characteristics used in training, they could be used to track accuracy during training.

Transcranial magnetic stimulation and functional magnet resonance imaging evaluation of adductor spasmodic dysphonia during phonation.

BACKGROUND: Reduced intracortical inhibition is a neurophysiologic finding in focal dystonia that suggests a broader problem of impaired cortical excitability within the brain. A robust understanding of the neurophysiology in dystonia is essential to elucidate the pathophysiology of the disorder and develop new treatments. The cortical silent period (cSP) is a reliable, non-invasive method to measure intracortical inhibition in the primary motor cortex associated with a muscle of interest. In adductor spasmodic dysphonia (AdSD), cSP of the laryngeal motor cortex (LMC) which directly corresponds to the affected musculature, the thyroarytenoid (TA), has not been examined. OBJECTIVE: This work evaluated the cSP of the LMC and the relationship between cSP and functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) activation in people with AdSD (n = 12) compared to healthy controls (CTL, n = 14). RESULTS: Shortened LMC cSP were observed bilaterally in people with AdSD vs CTL (F(1, 99) = 19.5226, p < 0.0001), with a large effect size (η2 = 0.1834). Between-group fMRI analysis revealed greater activation in bilateral LMC in the AdSD > CTL contrast as compared to CTL > AdSD contrast. Correlation analysis showed that people with AdSD have positive correlation of left LMC BOLD activation and the cSP. Further, the right LMC cSP lacks either positive or negative associations with BOLD activation. CTL individuals displayed both positive and negative correlations between cSP and BOLD activation in the left LMC. In CTL, the LMC cSP and BOLD activation showed exclusively negative correlations in both hemispheres. CONCLUSION: In AdSD, the cortical activation during phonation may not be efficiently or effectively associated with inhibitory processes, leading to muscular dysfunction. These findings may give insight into the maladaptive cortical control during phonation in people with AdSD.

Impaired Movement Scaling and Reduced Synchrony with Vestibule Closure Characterize Swallowing in Severe Dysphagia.

The contribution of hyoid and laryngeal movement deficits to penetration or aspiration in dysphagia is unclear, partly due to large variations in normal hyolaryngeal kinematics for swallowing. In healthy volunteers, laryngeal and hyoid kinematics relate to the requirements for laryngeal vestibule closure suggesting a central schematic control of movement magnitude and patterning for airway protection. Our first aim was to determine if patients with severe dysphagia showed evidence of an impaired swallowing schema, by examining if their kinematic measures were related to their hyolaryngeal space before swallow onset, and if hyolaryngeal movement synchrony for vestibule closure was disrupted. Our second aim was to determine the kinematic measures that predicted bolus penetration and aspiration in dysphagia. The methods included two-dimensional measures of the hyoid and laryngeal anterior and superior displacement and velocity, and the change in laryngeal vestibule area made from videofluoroscopic swallow recordings of 21 healthy volunteers and 21 patients with dysphagia on tube feeding secondary to the stroke or head and neck cancer. The results demonstrated that the patients did not adapt their hyolaryngeal movements during swallowing to their initial hyolaryngeal space. Further, none of the patients' measures of hyoid or laryngeal peak velocity timing were synchronized with vestibule closure, demonstrating a disorganized movement patterning. Laryngeal elevation peak velocity independently predicted penetration and aspiration. In conclusion, the central schema for swallowing patterning was disturbed, impairing the integration of kinematic actions for airway protection in severe dysphagia, while laryngeal peak elevation velocity predicted penetration and aspiration on patient swallows.

Laryngeal Vibration Increases Spontaneous Swallowing Rates in Chronic Oropharyngeal Dysphagia: A Proof-of-Principle Pilot Study.

Previously, vibratory stimulation increased spontaneous swallowing rates in healthy volunteers indicating that sensory stimulation excited the neural control of swallowing. Here, we studied patients with severe chronic dysphagia following brain injury or radiation for head and neck cancer to determine if sensory stimulation could excite an impaired swallowing system. We examined (1) if laryngeal vibratory stimulation increased spontaneous swallowing rates over sham (no stimulation); (2) the optimal rate of vibration, device contact pressure, and vibratory mode for increasing swallowing rates; and (3) if vibration altered participants' urge to swallow, neck comfort, and swallow initiation latency. Vibration was applied to the skin overlying the thyroid lamina bilaterally in thirteen participants to compare vibratory rates 30, 70, 110, 150, or 70 + 110 Hz, different devices to neck pressures (2, 4, or 6 kilopascals), and pulsed versus continuous vibration. Swallows were confirmed from recordings of laryngeal accelerometry and respiratory apneas and viewing neck movement. Participants' swallowing rates, urge to swallow, discomfort levels, and swallow initiation latencies were measured. Vibration at 70 Hz and at 110 Hz significantly increased swallowing rates over sham. All vibratory frequencies except 70 + 100 Hz increased participants' urge to swallow, while no pressures or modes were optimal for increasing urge to swallow. No conditions increased discomfort. Vibration did not reduce measures of swallow initiation latency using accelerometry. In conclusion, as non-invasive neck vibration overlying the larynx increased swallowing rates and the urge to swallow without discomfort in patients with chronic dysphagia, the potential for vibratory stimulation facilitating swallowing during dysphagia rehabilitation should be investigated.

Consensus-Based Attributes for Identifying Patients With Spasmodic Dysphonia and Other Voice Disorders.

Importance: A roadblock for research on adductor spasmodic dysphonia (ADSD), abductor SD (ABSD), voice tremor (VT), and muscular tension dysphonia (MTD) is the lack of criteria for selecting patients with these disorders. Objective: To determine the agreement among experts not using standard guidelines to classify patients with ABSD, ADSD, VT, and MTD, and develop expert consensus attributes for classifying patients for research. Design, Setting and Participants: From 2011 to 2016, a multicenter observational study examined agreement among blinded experts when classifying patients with ADSD, ABSD, VT or MTD (first study). Subsequently, a 4-stage Delphi method study used reiterative stages of review by an expert panel and 46 community experts to develop consensus on attributes to be used for classifying patients with the 4 disorders (second study). The study used a convenience sample of 178 patients clinically diagnosed with ADSD, ABSD, VT MTD, vocal fold paresis/paralysis, psychogenic voice disorders, or hypophonia secondary to Parkinson disease. Participants were aged 18 years or older, without laryngeal structural disease or surgery for ADSD and underwent speech and nasolaryngoscopy video recordings following a standard protocol. Exposures: Speech and nasolaryngoscopy video recordings following a standard protocol. Main Outcomes and Measures: Specialists at 4 sites classified 178 patients into 11 categories. Four international experts independently classified 75 patients using the same categories without guidelines after viewing speech and nasolaryngoscopy video recordings. Each member from the 4 sites also classified 50 patients from other sites after viewing video clips of voice/laryngeal tasks. Interrater κ less than 0.40 indicated poor classification agreement among rater pairs and across recruiting sites. Consequently, a Delphi panel of 13 experts identified and ranked speech and laryngeal movement attributes for classifying ADSD, ABSD, VT, and MTD, which were reviewed by 46 community specialists. Based on the median attribute rankings, a final attribute list was created for each disorder. Results: When classifying patients without guidelines, raters differed in their classification distributions (likelihood ratio, χ2 = 107.66), had poor interrater agreement, and poor agreement with site categories. For 11 categories, the highest agreement was 34%, with no κ values greater than 0.26. In external rater pairs, the highest κ was 0.23 and the highest agreement was 38.5%. Using 6 categories, the highest percent agreement was 73.3% and the highest κ was 0.40. The Delphi method yielded 18 attributes for classifying disorders from speech and nasolaryngoscopic examinations. Conclusions and Relevance: Specialists without guidelines had poor agreement when classifying patients for research, leading to a Delphi-based development of the Spasmodic Dysphonia Attributes Inventory for classifying patients with ADSD, ABSD, VT, and MTD for research.

Spasmodic Dysphonia: A Review. Part 2: Characterization of Pathophysiology.

Objective The purpose of this review is to describe the recent advances in characterizing spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. The pathophysiology is poorly understood, and there are diagnostic difficulties. Data Sources PubMed, Google Scholar, and Cochrane Library. Review Methods The data sources were searched using the following search terms: ( spasmodic dysphonia or laryngeal dystonia) and ( etiology, aetiology, diagnosis, pathogenesis, or pathophysiology). Conclusion The diagnosis of spasmodic dysphonia can be difficult due to the lack of a scientific consensus on diagnostic criteria and the fact that other voice disorders may present similarly. Confusion can arise between spasmodic dysphonia and muscle tension dysphonia. Spasmodic dysphonia symptoms are tied to particular speech sounds, whereas muscle tension dysphonia is not. With the advent of more widespread use of high-speed laryngoscopy and videokymography, measures of the disruptions in phonation and delays in the onset of vocal fold vibration after vocal fold closure can be quantified. Recent technological developments have expanded our understanding of the pathophysiology of spasmodic dysphonia. Implications for Practice A 3-tiered approach, involving a questionnaire, followed by speech assessment and nasolaryngoscopy is the most widely accepted method for making the diagnosis in most cases. More experimental and invasive techniques such as electromyography and neuroimaging have been explored to further characterize spasmodic dysphonia and aid in diagnosing difficult cases.

Spasmodic Dysphonia: A Review. Part 1: Pathogenic Factors.

Objective The purpose of this review is to describe the recent advances in identifying possible factors involved in the pathogenesis of spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. Pathogenesis of the disorder is poorly understood. Data Sources PubMed, Google Scholar, and Cochrane Library. Review Methods The data sources were searched using the following search terms: ( spasmodic dysphonia or laryngeal dystonia) and ( etiology, aetiology, diagnosis, pathogenesis, or pathophysiology). Conclusions Several potential etiological factors have been proposed by epidemiological, genetic, and neuropathological studies. Spasmodic dysphonia is a rare disorder primarily affecting females beginning in their 40s. Vocal tremor co-occurs in 30% to 60%. Large cohort studies identified risk factors such as a family history of neurological disorders including dystonia and tremor, recent viral illness, and heavy voice use. As none are rare events, a complex interactive process may contribute to pathogenesis in a small proportion of those at risk. Consequences to pathogenesis are neurological processes found in spasmodic dysphonia: loss of cortical inhibition, sensory processing disturbances, and neuroanatomical and physiological differences in the laryngeal motor control system. Implications for Practice Diagnosis of spasmodic dysphonia usually includes speech and laryngoscopic assessment. However, as diagnosis is sometimes problematic, measurement of neurophysiological abnormalities may contribute useful adjuncts for the diagnosis of spasmodic dysphonia in the future.

Vibration over the larynx increases swallowing and cortical activation for swallowing.

Sensory input can alter swallowing control in both the cortex and brainstem. Electrical stimulation of superior laryngeal nerve afferents increases reflexive swallowing in animals, with different frequencies optimally effective across species. Here we determined 1) if neck vibration overlying the larynx affected the fundamental frequency of the voice demonstrating penetration of vibration into the laryngeal tissues, and 2) if vibration, in comparison with sham, increased spontaneous swallowing and enhanced cortical hemodynamic responses to swallows in the swallowing network. A device with two motors, one over each thyroid lamina, delivered intermittent 10-s epochs of vibration. We recorded swallows and event-related changes in blood oxygenation level to swallows over the motor and sensory swallowing cortexes bilaterally using functional near infrared spectroscopy. Ten healthy participants completed eight 20-min conditions in counterbalanced order with either epochs of continuous vibration at 30, 70, 110, 150, and 70 + 110 Hz combined, 4-Hz pulsed vibration at 70 + 110 Hz, or two sham conditions without stimulation. Stimulation epochs were separated by interstimulus intervals varying between 30 and 45 s in duration. Vibration significantly reduced the fundamental frequency of the voice compared with no stimulation demonstrating that vibration penetrated laryngeal tissues. Vibration at 70 and at 150 Hz increased spontaneous swallowing compared with sham. Hemodynamic responses to swallows in the motor cortex were enhanced during conditions containing stimulation compared with sham. As vibratory stimulation on the neck increased spontaneous swallowing and enhanced cortical activation for swallows in healthy participants, it may be useful for enhancing swallowing in patients with dysphagia.NEW & NOTEWORTHY Vibratory stimulation at 70 and 150 Hz on the neck overlying the larynx increased the frequency of spontaneous swallowing. Simultaneously vibration also enhanced hemodynamic responses in the motor cortex to swallows when recorded with functional near-infrared spectroscopy (fNIRS). As vibrotactile stimulation on the neck enhanced cortical activation for swallowing in healthy participants, it may be useful for enhancing swallowing in patients with dysphagia.

Evaluation of the Cortical Silent Period of the Laryngeal Motor Cortex in Healthy Individuals.

Objective: This work aimed to evaluate the cortical silent period (cSP) of the laryngeal motor cortex (LMC) using the bilateral thyroarytenoid (TA) muscles with transcranial magnetic stimulation (TMS). Methods: In 11 healthy participants, fine-wire electromyography (EMG) was used to record bilateral TA muscle responses to single pulse TMS delivered to the LMC in both hemispheres. Peripheral responses to stimulation over the mastoid, where the vagus nerve exits the skull, were collected to verify the central origin of the cortical stimulation responses by comparing the latencies. Results: The cSP duration ranged from 41.7 to 66.4 ms. The peripherally evoked motor-evoked potential (MEP) peak occurred 5-9 ms earlier than the cortical responses (for both sides of TAs: p < 0.0001) with no silent period. The right TA MEP latencies were earlier than the left TA responses for both peripheral and cortical measures (p ≤ 0.0001). Conclusion: These findings demonstrate the feasibility of measuring cSP of LMC based on intrinsic laryngeal muscles responses during vocalization in healthy volunteers. Significance: The technique could be used to study the pathophysiology of neurological disorders that affect TA muscles, such as spasmodic dysphonia. Further, the methodology has application to other muscles of the head and neck not accessible using surface electrodes.

Evidence that an internal schema adapts swallowing to upper airway requirements.

KEY POINTS: To swallow food and liquid safely, airway protection is essential. Upward and forward movements of the hyoid and larynx in the neck during swallowing vary in magnitude between individuals. In healthy human adults, hyoid and laryngeal movements during swallowing were scaled by differences in initial upper airway area before swallowing. Individuals increased laryngeal elevation during swallowing in response to increased airway opening before swallowing. We show that when upper airway protection requirements change, individuals use an internal sensorimotor scaling system to adapt movements to maintain swallow safety. ABSTRACT: Hyoid and laryngeal movements contribute to laryngeal vestibule closure and upper oesophageal sphincter opening during swallowing. Evidence of an internal sensorimotor scaling system allowing individuals to achieve these functional goals is lacking. In speech, speakers adjust their articulatory movement magnitude according to the movement distance required to reach an articulatory target for intelligible speech. We investigated if swallowing is similar in that movement amplitude may be scaled by the functional goal for airway protection during swallowing, rather than by head and neck size. We hypothesized that healthy individuals adapt to their own anatomy by adjusting hyo-laryngeal movements to achieve closure of the upper airway. We also investigated if individuals would automatically compensate for changes in their initial hyo-laryngeal positions and area when head position was changed prior to swallowing. Videofluoroscopy was performed in 31 healthy adults. Using frame-by-frame motion analysis, anterior and superior hyoid and laryngeal displacement, and hyo-laryngeal area were measured prior to and during swallowing. Kinematic measurements during swallowing were examined for relationships with pharyngeal neck length, and initial hyo-laryngeal positions, length and area before swallowing. During swallowing, individuals altered laryngeal elevation magnitude to exceed hyoid elevation based on hyo-laryngeal length before swallowing. Anterior laryngeal displacement was related to initial larynx distance from the spine, while hyoid elevation was predicted by pharyngeal neck length and initial hyoid distance from the mandible prior to the swallow. In conclusion, individuals automatically adapt hyo-laryngeal movement during swallowing based on targets required for closing the hyo-laryngeal area for safe swallowing.

Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network.

Sour stimuli have been shown to upregulate swallowing in patients and in healthy volunteers. However, such changes may be dependent on taste-induced increases in salivary flow. Other mechanisms include genetic taster status (Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Weiffenbach JM. Physiol Behav 82: 109-114, 2004) and differences between sour and other tastes. We investigated the effects of taste on swallowing frequency and cortical activation in the swallowing network and whether taster status affected responses. Three-milliliter boluses of sour, sour with slow infusion, sweet, water, and water with infusion were compared on swallowing frequency and hemodynamic responses. The sour conditions increased swallowing frequency, whereas sweet and water did not. Changes in cortical oxygenated hemoglobin (hemodynamic responses) measured by functional near-infrared spectroscopy were averaged over 30 trials for each condition per participant in the right and left motor cortex, S1 and supplementary motor area for 30 s following bolus onset. Motion artifact in the hemodynamic response occurred 0-2 s after bolus onset, when the majority of swallows occurred. The peak hemodynamic response 2-7 s after bolus onset did not differ by taste, hemisphere, or cortical location. The mean hemodynamic response 17-22 s after bolus onset was highest in the motor regions of both hemispheres, and greater in the sour and infusion condition than in the water condition. Genetic taster status did not alter changes in swallowing frequency or hemodynamic response. As sour taste significantly increased swallowing and cortical activation equally with and without slow infusion, increases in the cortical swallowing were due to sour taste.

Using devices to upregulate nonnutritive swallowing in typically developing infants.

The role of various sensory stimuli for stimulating swallowing in infants may be of importance for assisting infants to develop oral feeding. We evaluated the swallowing mechanism response to two devices for increasing the rate of nonnutritive swallowing in two typically developing infant age groups, ages 2-4 mo and 7-9 mo. One device was a pacifier familiar to the infant; the other was a small vibrator placed on the skin overlying the thyroid cartilage. The rate of nonnutritive swallowing while infants were awake was compared in three 10-min conditions: at rest without stimulation (spontaneous); during nonnutritive sucking with a pacifier; and over 10 min containing 18 epochs of vibratory stimulation for 10 s each. To assess whether vibration on the throat over the laryngeal area altered respiration, the mean cycle length was compared between 10-min intervals either containing vibratory stimulation or without stimulation at rest. Both the pacifier and laryngeal vibration stimulation doubled the rate of swallowing in the infants with a mean age of 3 mo 16 days and infants with a mean age of 8 mo 8 days. No differences occurred in the mean respiratory cycle length between intervals with and without vibration in either age group. Results suggest that nonnutritive sucking, vibration, or both might be beneficial in enhancing swallowing in young infants. Because vibration on the neck would not interfere with oral transfer of liquid, it might provide additional stimulation for swallowing during oral feeding. Both stimulation types should be evaluated for enhancing swallowing in infants with immature swallowing skills.

Laryngeal Reflexes: Physiology, Technique, and Clinical Use.

This review examines the current level of knowledge and techniques available for the study of laryngeal reflexes. Overall, the larynx is under constant control of several systems (including respiration, swallowing and cough) as well as sensory motor reflex responses involving glossopharyngeal, pharyngeal, laryngeal, and tracheobronchial sensory receptors. Techniques for the clinical assessment of these reflexes are emerging and need to be examined for sensitivity and specificity in identifying laryngeal sensory disorders. Quantitative assessment methods for the diagnosis of sensory reductions and sensory hypersensitivity may account for laryngeal disorders, such as chronic cough, paradoxical vocal fold disorder, and muscular tension dysphonia. The development of accurate assessment techniques could improve our understanding of the mechanisms involved in these disorders.

Central Nervous System Control of Voice and Swallowing.

This review of the central nervous control systems for voice and swallowing has suggested that the traditional concepts of a separation between cortical and limbic and brain stem control should be refined and be more integrative. For voice production, a separation of the nonhuman vocalization system from the human learned voice production system has been posited based primarily on studies of nonhuman primates. However, recent humans studies of emotionally based vocalizations and human volitional voice production have shown more integration between these two systems than previously proposed. Recent human studies have shown that reflexive vocalization as well as learned voice production not involving speech involve a common integrative system. However, recent studies of nonhuman primates have provided evidence that some cortical activity vocalization and cortical changes occur with training during vocal behavior. For swallowing, evidence from the macaque and functional brain imaging in humans indicates that the control for the pharyngeal phase of swallowing is not primarily under brain stem mechanisms as previously proposed. Studies suggest that the initiation and patterning of swallowing for the pharyngeal phase is also under active cortical control for both spontaneous as well as volitional swallowing in awake humans and nonhuman primates.

Activation of upper airway muscles during breathing and swallowing.

The upper airway is a complex muscular tube that is used by the respiratory and digestive systems. The upper airway is invested with several small and anatomically peculiar muscles. The muscle fiber orientations and their nervous innervation are both extremely complex, and how the activity of the muscles is initiated and adjusted during complex behaviors is poorly understood. The bulk of the evidence suggests that the entire assembly of tongue and laryngeal muscles operate together but differently during breathing and swallowing, like a ballet rather than a solo performance. Here we review the functional anatomy of the tongue and laryngeal muscles, and their neural innervation. We also consider how muscular activity is altered as respiratory drive changes, and briefly address upper airway muscle control during swallowing.

The focal dystonias: current views and challenges for future research.

The most common forms of dystonia are those that develop in adults and affect a relatively isolated region of the body. Although these adult-onset focal dystonias are most prevalent, knowledge of their etiologies and pathogenesis has lagged behind some of the rarer generalized dystonias, in which the identification of genetic defects has facilitated both basic and clinical research. This summary provides a brief review of the clinical manifestations of the adult-onset focal dystonias, focusing attention on less well understood clinical manifestations that need further study. It also provides a simple conceptual model for the similarities and differences among the different adult-onset focal dystonias as a rationale for lumping them together as a class of disorders while at the same time splitting them into subtypes. The concluding section outlines some of the most important research questions for the future. Answers to these questions are critical for advancing our understanding of this group of disorders and for developing novel therapeutics.

Relative Efficacy of Swallowing versus Non-swallowing Tasks in Dysphagia Rehabilitation: Current Evidence and Future Directions.

Clinical trials published in 2012 and the first six months of 2013 were reviewed. These involved either traditional dysphagia therapy, indirect methods not involving dysphagia therapy or a combination of direct and indirect methods. Of 27 studies, 7 were RCTs, 5 were controlled clinical trials and the remainder were uncontrolled case series. Sixteen studies combined an indirect treatment with traditional dysphagia therapy; only one study examined one technique for direct swallowing therapy. Effect sizes were computed and contrasted for each trial. Traditional dysphagia therapy had small to moderate effect sizes (between 0.3 and 0.6) while spontaneous recovery in acute stroke had effect sizes of 1.2. Placebo effects on patient ratings of degree of improvement on swallowing were estimated as small to moderate. To improve effect sizes, adaptive research designs are needed to develop the optimal methods and dosages of therapy before future clinical trials.