Initiation Of Swallow Research Articles

Isolated Dysphagia: An Unusual Presentation of a Lateral Medullary Lesion

Dysphagia is a complex symptom often attributed to mechanical obstruction, dysmotility, or a neurologic origin. Thus, the process of eliciting the etiology may poise a diagnostic challenge in atypical presentations. A 60-year-old male who presented with a sudden onset of dysphagia and feeling of food bolus impaction in the absence of other symptoms. The patient has had trouble swallowing any fluids, pills, or food for five days. He has not had any prior episodes of dysphagia. His past medical history includes transient ischemic attacks, hypertension, hyperlipidemia, diabetes mellitus type 2, and hypothyroidism. On presentation, the patient had elevated blood pressure, severe dysphagia, mild right facial droop, hypernatremia, and elevated serum glucose levels. Initial barium swallow showed narrowing in subglottic esophagus and subsequent Esophagogastroduodenoscopy (EGD) revealed a cricopharyngeal web dilated up to 51 Fr without any resistance. There was no improvement in the patient's symptoms after the procedure. Initial neurological assessment was unremarkable. However, further neurological evaluation was needed after profound pharyngeal muscular weakness and nearly absent swallow initiation was shown on a modified barium swallow. Magnetic resonance imaging (MRI) of the brain was inconclusive, so digital subtraction angiography (DSA) of head and neck was done and suggested subacute infarct of right pontomedullary junction due to terminal segmental right vertebral artery occlusion. Due to the severity of dysphagia, the patient underwent a percutaneous endoscopic feeding gastrostomy (PEG) placement, tolerated tube feeds, and was discharged nine days later. Five weeks after discharge, dysphagia was significantly improved from initial evaluation and overall swallow was safe for oral intake. This case illustrates that subacute lateral medullary lesions can present with dysphagia as the main symptom at the onset. The initial EGD showed a cricopharyngeal web which shifted the thinking towards a gastrointestinal cause for dysphagia. However, having a strong clinical suspicion of a neurogenic origin led us to this diagnosis. The neurogenic etiology of an acute or subacute oropharyngeal dysphagia should be suspected in the practice of gastroenterology or emergency department, especially if the history is not typical for food impaction that occurs during swallowing and when the patient has risk factors conducive to neurovascular disease.1832_A Figure 1. Endoscopic image showing cricopharyngeal web1832_B Figure 2. Modified barium swallow showing pharyngeal dysphagia with essentially absent swallow initiation1832_C Figure 3. CT angiogram of the neck showing focal high-grade narrowing of the dominant right vertebral V3 segment artery

Central Respiration and Mechanical Ventilation in the Gating of Swallow With Breathing.

Swallow-breathing coordination safeguards the lower airways from tracheal aspiration of bolus material as it moves through the pharynx into the esophagus. Impaired movements of the shared muscles or structures of the aerodigestive tract, or disruptions in the interaction of brainstem swallow and respiratory central pattern generators (CPGs) result in dysphagia. To maximize lower airway protection these CPGs integrate respiratory rhythm generation signals and vagal afferent feedback to synchronize swallow with breathing. Despite extensive study, the roles of central respiratory activity and vagal feedback from the lungs as key elements for effective swallow-breathing coordination remain unclear. The effect of altered timing of bronchopulmonary vagal afferent input on swallows triggered during electrical stimulation of the superior laryngeal nerves or by injection of water into the pharyngeal cavity was studied in decerebrate, paralyzed, and artificially ventilated cats. We observed two types of single swallows that produced distinct effects on central respiratory-rhythm across all conditions: post-inspiratory type swallows disrupted central-inspiratory activity without affecting expiration, whereas expiratory type swallows prolonged expiration without affecting central-inspiratory activity. Repetitive swallows observed during apnea reset the E2 phase of central respiration and produced facilitation of swallow motor output nerve burst durations. Moreover, swallow initiation was negatively modulated by vagal feedback and was reset by lung inflation. Collectively, these findings support a novel model of reciprocal inhibition between the swallow CPG and inspiratory or expiratory cells of the respiratory CPG where lung distension and phases of central respiratory activity represent a dual peripheral and central gating mechanism of swallow-breathing coordination.

Impact of recurrent laryngeal nerve lesion on oropharyngeal muscle activity and sensorimotor integration in an infant pig model.

The successful performance of a swallow requires dynamic integration between a wide range of sensory inputs and muscle activities to produce the coordinated kinematics of oropharyngeal structures. Damage to the recurrent laryngeal nerve (RLN) produces dysphagia in infants, with food or liquid entering the airway despite this nerve having minimal direct sensory or motor connections to the act of swallowing, apart from vocal fold closure. Previous results have demonstrated that a complete RLN lesion disrupts both performance and kinematics before initiation of the pharyngeal swallow in infants. We tested the hypothesis that a RLN lesion produces changes in the normal activity of oral floor, tongue, and infrahyoid muscles during a swallow. We recorded swallowing in our validated infant pig model, with synchronous high-speed imaging and fine-wire, chronic electromyography. We found changes in the timing, duration, and amplitude of the motor pattern in an array of muscles that are supplied by several different cranial and cervical nerves. Some of these changes in muscle activity are associated with the preparatory aspects of bolus aggregation or movement and so occur before the pharyngeal swallow. Taken with previous biomechanical results, these patterns suggest an intricate brain stem sensorimotor integration that occurs as part of a swallow. In particular, the execution of oral motor function is changed as a result of this simple lesion. NEW & NOTEWORTHY Damage to the recurrent laryngeal nerve compromises swallowing despite an absent or minimal contribution to either the motor or sensory aspects of this function. This study documents EMG changes, following RLN lesion, to non-RLN innervated muscles that are active during swallowing in an infant model. Some of these muscles fire before the pharyngeal swallow and are associated with the preparatory aspects of bolus aggregation and movement, suggesting important sensorimotor integration at a brain stem level.

New insights into a decerebrate feline model of swallow‐breathing coordination

In the medulla, the swallow and respiratory central pattern generators (CPGs) interact to coordinate swallow initiation and permit swallow execution during the expiratory phase of breathing. Disruption of swallow‐breathing coordination can result in dysphagia, which is a major cause of morbidity and mortality in many neuro‐muscular diseases, especially stroke. Despite extensive study, the precise mechanisms of swallow‐breathing coordination are not known. We tested the hypothesis that both central inspiratory activity and vagal feedback from the lungs are key elements for effective swallow‐breathing coordination. Swallows were triggered by electrical stimulation of the superior laryngeal nerves (SLN) or by injection of water into the pharyngeal cavity in decerebrate, paralyzed and artificially ventilated cats while motor activities were recorded from phrenic, hypoglossal, lumbar and vagal nerves. Mechanical ventilation was either triggered by central inspiratory activity or set independently from the phrenic activity to alter the timing of bronchopulmonary vagal afferent input and allow analysis of its influence on swallow‐breathing coordination. We observed two types of swallows that produced opposite effects on central respiratory‐rhythm resetting across all conditions: post‐Inspiratory type swallows disrupted central I activity without affecting expiration, whereas expiratory type swallows prolonged expiration without affecting central inspiratory activity. Repetitive swallows observed during apnea reset the E2 phase of central respiration and produced facilitation of swallow motor output. Moreover, swallow initiation was negatively modulated by vagal feedback and was reset by lung inflation. Collectively, these findings support a reciprocal inhibition between central inspiration and the swallow CPG and they are consistent with a role for pulmonary stretch receptors in the coordination between brainstem CPGs for breathing and swallowing. They may also prove relevant for healthcare management of dysphagia.Support or Funding InformationOT2OD023854‐01, HL109025This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of hypercapnia on the swallow‐breathing relationship in cats

Swallow‐breathing coordination is critical for maintaining a clear airway during the act of swallowing. Swallows can occur during all phases of breathing, however, they are primarily initiated during expiration. The interaction between central pattern generators for swallowing and breathing contribute to this phase preference. While hypercapnia has known effects on the breathing central pattern generator, the effects of elevated CO2 on swallow‐breathing coordination are unknown. We examined the influence of hypercapnia on swallow‐breathing phase preference in the cat. Swallowing was induced in anesthetized spontaneously breathing cats by injection of water into the oropharynx and experiments were conducted under conditions of room air, 5% CO2, or 10% CO2. Electromyogram activity was measured using bipolar electrodes inserted into laryngeal and pharyngeal muscles (mylohyoid, geniohyoid, thyrohyoid, and thyropharyngeus), parasternal muscles and costal diaphragm. In cats breathing room air, 71% of swallows occurred during expiration (E), 12% during inspiration (I), 10% during the transition from inspiration to expiration (I to E), and 7% during the transition from expiration to inspiration (E to I). Under hypercapnic conditions swallows occurred more frequently during inspiration with 80% (5% CO2) and 68% (10% CO2) occurring during either the I or the E to I phases of breathing, and 16% (5% CO2) and 25% (10% CO2) occurring during expiration. These preliminary results suggest hypercapnia may affect swallow‐breathing coordination by causing the initiation of swallow to occur in more inspiratory phases (I and E to I).Support or Funding InformationSupported by R00‐HL 111215, NIH HL 103415, and 1OT20D001983.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Longitudinal Evaluation of Swallowing with Videofluoroscopy in Patients with Locally Advanced Head and Neck Cancer After Chemoradiation.

The aim of this study was to investigate the prevalence, severity, and pattern of evolution of swallowing impairments encountered in head and neck cancer (HNC) patients before and after chemoradiation (CRT) with videofluoroscopy of swallowing study (VFSS), using the modified barium swallow impairment profile (MBSImP) protocol and scoring system, and to determine the appropriate time points in which these patients should undergo VFSS post-CRT. A prospective cohort of 69 patients with locally advanced HNC underwent VFSS with the MBSImP protocol at 5 evaluation points: pre-CRT, and 1, 3, 6, and 12months post-CRT. VFSS was scored with MBSImP, penetration-aspiration scale (PAS), and swallowing performance status (SPS) scale. Statistical analysis was performed only for the 12-month disease-free subset of patients. MBSImP, PAS, and SPS scale scores reached their peak at 3months post-CRT and improved at 6-12months, but without returning at pre-treatment levels. Base of tongue retraction, initiation of pharyngeal swallow, epiglottic movement, laryngeal vestibule closure, and laryngeal elevation were the most frequently observed impaired MBSImP components. Epiglottic movement significantly improved (p = 0.009) and laryngeal vestibule closure significantly deteriorated (p = 0.042) over time (Friedman test). Severe swallowing deficits and high aspiration rates are observed in HNC patients pre-CRT, which further deteriorate post-CRT, peak at 3months, and despite slight improvement, persist over time. We suggest that these patients, regardless of the presence of subjective dysphagia, should undergo VFSS both before and 3months post-CRT, and also if possible, 1month post-CRT, in order to facilitate implementation of early swallowing rehabilitation.

Effects of pharyngeal electrical stimulation on swallowing performance.

Pharyngeal electrical stimulation (PEStim) has been found to facilitate voluntary swallowing. This study investigated how PEStim contributed to modulation of swallowing function in 15 healthy humans. In the involuntary swallowing test, water was injected onto the pharynx at 0.05 ml/s and the onset latency of the first swallow was measured. In the voluntary swallowing test, subjects swallowed their own saliva as quickly as possible for 30 s and the number of swallows was counted. Voluntary and involuntary swallowing was evaluated before (baseline), immediately after, and every 10 min after 10-min PEStim for 60 min. A voluntary swallowing test with simultaneous 30-s PEStim was also conducted before and 60 min after 10-min PEStim. The number of voluntary swallows with simultaneous PEStim significantly increased over 60 min after 10-min PEStim compared with the baseline. The onset latency of the first swallow in the involuntary swallowing test was not affected by 10-min PEStim. The results suggest that PEStim may have a long-term facilitatory effect on the initiation of voluntary swallowing in healthy humans, but not on peripherally-evoked swallowing. The physiological implications of this modulation are discussed.

Effects of age and viscosity on food transport and breathing-swallowing coordination during eating of two-phase food in nursing home residents.

When eating food that contains both liquid and solid phases, the liquid component frequently enters the hypopharynx before swallowing and can increase the risk of aspiration. Thus, we examined whether the initial viscosity of mixed consistency food could alter pre-swallow food transport and breathing-swallowing coordination in older adults. Fiberoptic endoscopy was recorded while 18 healthy young adults and 19 older adults ate 5 g of steamed rice combined with 3 mL of blue-dye water. Liquid viscosity was set at three levels by the addition of a thickening agent (0 wt%, thin; 2 wt%, thicker; 4 wt%, higher-viscosity, respectively). We measured the timing of swallow initiation and its corresponding respiratory phase for each participant. For thin mixed consistency food, whereas the timing of swallow initiation was comparable between young and older participants, swallowing was initiated during inspiration significantly more often in older participants (31.6 %) than in young participants (5.6 %). In contrast, the timing of swallow initiation was delayed in older participants for thicker and higher-viscosity foods, although swallowing was commonly initiated during expiration in both groups. In older adults, we observed that swallow initiation function was preserved for thin mixed consistency samples, but breathing-swallowing coupling was diminished. For higher-viscosity foods, swallow initiation was delayed in this group, but breathing-swallowing coordination was not disturbed, probably as a result of the slow bolus flow into the hypopharynx. Thus, it appears the initial viscosity of mixed consistency food profoundly affects food transport before swallowing as well as breathing-swallowing coordination in nursing home residents. Geriatr Gerontol Int 2017; 17: 2171-2177.

Central inhibition of initiation of swallowing by systemic administration of diazepam and baclofen in anaesthetized rats.

Dysphagia is caused not only by neurological and/or structural damage but also by medication. We hypothesized memantine, dextromethorphan, diazepam, and baclofen, all commonly used drugs with central sites of action, may regulate swallowing function. Swallows were evoked by upper airway (UA)/pharyngeal distension, punctate mechanical stimulation using a von Frey filament, capsaicin or distilled water (DW) applied topically to the vocal folds, and electrical stimulation of a superior laryngeal nerve (SLN) in anesthetized rats and were documented by recording electromyographic activation of the suprahyoid and thyrohyoid muscles and by visualizing laryngeal elevation. The effects of intraperitoneal or topical administration of each drug on swallowing function were studied. Systemic administration of diazepam and baclofen, but not memantine or dextromethorphan, inhibited swallowing evoked by mechanical, chemical, and electrical stimulation. Both benzodiazepines and GABAA receptor antagonists diminished the inhibitory effects of diazepam, whereas a GABAB receptor antagonist diminished the effects of baclofen. Topically applied diazepam or baclofen had no effect on swallowing. These data indicate that diazepam and baclofen act centrally to inhibit swallowing in anesthetized rats.NEW & NOTEWORTHY Systemic administration of diazepam and baclofen, but not memantine or dextromethorphan, inhibited swallowing evoked by mechanical, chemical, and electrical stimulation. Both benzodiazepines and GABAA receptor antagonists diminished the inhibitory effects of diazepam, whereas a GABAB receptor antagonist diminished the effects of baclofen. Topical applied diazepam or baclofen was without effect on swallowing. Diazepam and baclofen act centrally to inhibit swallowing in anesthetized rats.

Dysphagia in infants with single ventricle anatomy following stage 1 palliation: Physiologic correlates and response to treatment.

Deficits in swallowing physiology are a leading morbidity for infants with functional single ventricles and systemic outflow tract obstruction following stage 1 palliation. Despite the high prevalence of this condition, the underlying deficits that cause this post-operative impairment remain poorly understood. Identify the physiologic correlates of dysphagia in infants with functional single ventricles and systemic outflow tract obstruction following stage 1 palliative surgery. Postoperative fiberoptic laryngoscopies and videofluoroscopic swallow studies (VFSS) were conducted sequentially on infants with functional single ventricles following stage 1 palliative surgery. Infants were dichotomized as having normal or impaired laryngeal function based on laryngoscopy findings. VFSS were evaluated frame-by-frame using a scale that quantifies performance within 11 components of swallowing physiology. Physiologic attributes within each component were categorized as high functioning or low functioning based on their ability to support milk ingestion without bolus airway entry. Thirty-six infants (25 male) were included in the investigation. Twenty-four underwent the Norwood procedure and twelve underwent the Hybrid procedure. Low function physiologic patterns were observed within multiple swallowing components during the ingestion of thin barium as characterized by ≥4 sucks per swallow (36%), initiation of pharyngeal swallow below the level of the valleculae (83%), and incomplete late laryngeal vestibular closure (56%) at the height of the swallow. Swallowing deficits contributed to aspiration in 50% of infants. Although nectar thick liquids reduced the rate of aspiration (P = .006), aspiration rates remained high (27%). No differences in rates of penetration or aspiration were observed between infants with normal and impaired laryngeal function. Deficits in swallowing physiology contribute to penetration and aspiration following stage 1 palliation among infants with normal and impaired laryngeal function. Although thickened liquids may improve airway protection for select infants, they may inhibit their ability to extract the bolus and meet nutritional needs.

Esophageal Dysmotility in a Case of Undifferentiated Connective Tissue Disorder

Connective-tissue diseases (CTDs) are a variegated group of disorders manifesting with a wide range of clinical manifestations and laboratory abnormalities. Some patients present with a significant overlap of symptoms preventing them from being categorized as having a specific CTD. These patients are often diagnosed with undifferentiated connective tissue disorder (UCTD). We here present a very rare case of a relatively young woman with UCTD who presented with worsening dysphagia secondary to both striated and smooth muscle dysfunction. A 50-year-old woman with medical comorbidities of Hashimoto's thyroiditis, dyslipidemia had presented to the rheumatology clinic for diffuse myalgias and generalized weakness. Patient's laboratory testing was significant for elevated creatine phosphokinase (CPK of 281 IU/L), positive thyroid peroxidase antibody (>1000 IU/mL), thyroglobulin antibody (167 IU IU/L) and antinuclear antibody (1: 160) but other CTD specific antibodies (anti-Jo-1, antiribosomal P protein, anti-dsDNA, antihistone, anti-RNP, anti-Sm and anti-Scl-70) were negative. Patient was diagnosed with possible statin induced myopathy. However patient did not symptomatically improve after cessation of statins and was found to have persistently elevated CPK. Patient subsequently developed progressively worsening dysphagia to both solids and liquids over the next four years. Esophagogastroduodenoscopy was unremarkable while a barium esophagogram revealed pooling of contrast in the vallecular region with minimal aspiration. There was narrowing of lower esophagus with proximal dilation as well, suggestive of achalasia (Figure-1a/1b). Barium swallow with video fluoroscopy demonstrated delayed initiation of swallowing. High resolution manometry was consistent with type I achalasia (Figure-2 and 3). This rare case demonstrates dysphagia secondary to dysfunction of both striated and smooth muscles in setting of possible UCTD. UCTD is characterized by presence of positive antinuclear antibodies and symptoms for duration of at least 3 years. Patient also had chronic autoimmune thyroiditis which is commonly seen in patients with UCTD. Another distinct possibility in this case includes HMG-coA reductase antibody associated autoimmune myopathy which can have smooth muscle involvement. This case was remarkable given that initial rheumatological diagnosis of simple statin induced myopathy had to be reconsidered in light of imaging and manometric evidence.Figure 1Figure 2Figure 3

Respiratory-swallowing coordination in normal subjects: Lung volume at swallowing initiation

This study was designed to investigate the significance of bolus types and volumes, delivery methods and swallowing instructions on lung volume at swallowing initiation in normal subjects in a single experiment using a multifactorial approach. Our broad range goal was to determine optimal lung volume range associated with swallowing initiation to provide training targets for dysphagic patients with disordered respiratory-swallow coordination. Our hypothesis was that swallows would be initiated within a limited range of quiet breathing lung volumes regardless of bolus volume, consistency or task. Results confirmed this hypothesis and revealed that swallows were initiated at mean lung volume=244ml. Cued swallows were initiated at lower quiet breathing volumes than un-cued swallows (cued=201ml; un-cued=367ml). Water boluses were initiated at slightly higher quiet breathing volumes than solids. Data suggest that swallows occur within a restricted range of lung volumes with variation due to instructions, bolus type and other experimental variables.

Factors Associated With Gastrostomy Tube Removal in Patients With Dysphagia After Stroke.

Gastrostomy feeding tubes are commonly placed in patients with dysphagia after stroke. The subsequent removal of the tube is a primary goal during rehabilitation. The purpose of our review was to identify predictors and factors associated with gastrostomy tube removal in patients with dysphagia after stroke. We conducted a literature review following the PRISMA statement and included the search databases PubMed, Scopus, Web of Science, and CINAHL. Articles were included in the final analysis per predefined inclusion and exclusion criteria. Our search retrieved a total of 853 results consisting of 416 articles (after eliminating duplicates). Six articles met our final eligibility criteria. The following factors were identified in at least 1 article as being significantly associated with gastrostomy tube removal: reduced age, decreased number of comorbidities, prolonged inpatient rehabilitation stay, absence of bilateral stroke, nonhemorrhagic stroke, reduced dysphagia severity, absence of aspiration, absence of premature bolus loss, and timely initiation of pharyngeal swallow. Aspiration was the only factor that was investigated by 2 studies-both using multiple regression and both showing stable results, with absence of aspiration increasing the chances for tube removal. In conclusion, little is known about factors associated with gastrostomy tube removal in patients with dysphagia after stroke. Most of the identified factors are associated with stroke or disease severity; however, the role of the individual factors remains unclear. The strongest predictor appears to be absence of aspiration on modified barium swallow studies emphasizing the importance of instrumental swallow studies in this patient population.

Chemical Sensing Regulates Mastication/Swallowing.

Mastication and swallowing are the first stage of digestion involving several motor processes such as food intake, intra-oral food transport, bolus formation and chewing and swallowing reflex. These complicated motor functions are accomplished by the well-coordinated activities in the jaw, hyoid, tongue, facial and pharyngeal muscles. Although the basic activity patterns of these movements are controlled by the brainstem pattern generators, these movements generate various peripheral sensory inputs. Among the sensory inputs, it is well-known that somatic sensory inputs play important roles in reflexively modulating the movements so that the final motor outputs fit the environmental demand. However, little is known about the effects of chemical sensory inputs such as taste and olfaction originating from the ingested foods by these movements. A possible reason could be raised that cognition of the chemical sensory inputs at the higher brain also influences the movements, so it is difficult to discuss the neural mechanisms underlying the observed effect. In this review, we focus on the effects of chemical sensory inputs on the masticatory movements and initiation of swallowing. We first summarize chemical sensory inputs occurring during mastication and swallowing, and their receptive mechanisms. In addition, we will introduce the effect of application of monosodium L-glutamate (MSG) solution as an umami taste to the oropharynx on the swallow initiation which is involuntary controlled and the possible neural mechanisms underlying this effect is discussed.

The Use of Neuroplastic Principles Affects the Swallow Motor Plan of a Patient in Severe Cognitive Decline: A Case Study

Dysphagia is common in patients with dementia. Dysphagia occurs as a result of changes in the sensory and motor function of the swallow (Easterling, 2007). It is known that the central nervous system can undergo experience-dependent plasticity, even in those individuals with dementia (Park & Bischof, 2013). The purpose of this study was to explore whether or not the use of neuroplastic principles would improve the swallow motor plan and produce positive outcomes of a patient in severe cognitive decline. The disordered swallow motor plan was manipulated by focusing on a neuroplastic principles of frequency (repetition), velocity of movement (speed of presentation), reversibility (Use it or Lose it), specificity and adaptation, intensity (bolus size), and salience (Crary & Carnaby-Mann, 2008). After five therapeutic sessions, the patient progressed from holding solids in her mouth with decreased swallow initiation to independently consuming a regular diet with full range of liquids with no oral retention and no verbal cues.

A Randomized Trial Comparing Two Tongue-Pressure Resistance Training Protocols for Post-Stroke Dysphagia.

The objective of this study was to compare the outcomes of two tongue resistance training protocols. One protocol ("tongue-pressure profile training") emphasized the pressure-timing patterns that are typically seen in healthy swallows by focusing on gradual pressure release and saliva swallowing tasks. The second protocol ("tongue-pressure strength and accuracy training") emphasized strength and accuracy in tongue-palate pressure generation and did not include swallowing tasks. A prospective, randomized, parallel allocation trial was conducted. Of 26 participants who were screened for eligibility, 14 received up to 24 sessions of treatment. Outcome measures of posterior tongue strength, oral bolus control, penetration-aspiration and vallecular residue were made based on videofluoroscopy analysis by blinded raters. Complete data were available for 11 participants. Significant improvements were seen in tongue strength and post-swallow vallecular residue with thin liquids, regardless of treatment condition. Stage transition duration (a measure of the duration of the bolus presence in the pharynx prior to swallow initiation, which had been chosen to capture impairments in oral bolus control) showed no significant differences. Similarly, significant improvements were not seen in median scores on the penetration-aspiration scale. This trial suggests that tongue strength can be improved with resistance training for individuals with tongue weakness following stroke. We conclude that improved penetration-aspiration does not necessarily accompany improvements in tongue strength; however, tongue-pressure resistance training does appear to be effective for reducing thin liquid vallecular residue.

Initiation of Pharyngeal Response during Discrete Swallowing and Chew-swallowing in Healthy Subjects.

The aim of this study was to measure the initiation of pharyngeal swallowing during discrete swallowing and during chew-swallowing in younger and older healthy subjects and to determine the normal range of the stage transition duration (STD) for different food boluses. The correlations between STDs were investigated. Twenty-eight younger subjects (< 60 years old) and 25 older subjects (≥ 60 years old) were enrolled. While in the sitting position, the subjects swallowed 10 ml of thin liquid barium (LQ), 8 g of corned beef hash with barium (CB), 8 g of cookie with barium (CK), and a two-phase mixture of 4 g of corned beef hash with barium and 5 ml of thin liquid barium (MX). A videofluoroscopic examination of swallowing was performed at 30 frames/s in the lateral projection. The delay in pharyngeal swallowing (i.e., STD) was measured. The normal range (mean ± 2SD) of STDs for each bolus type was determined, and correlations were calculated to examine the relationship among STDs. The median STDs for LQ, CB, CK, and MX in all subjects were 0.0, 1.2, 2.4, and 1.9 s, respectively. The STDs were prolonged for CB, CK, and MX compared with LQ. Additionally, the median STD was longer for LQ, CB, and CK in older than in younger subjects. No significant correlations were found between STDs except for those between CB and CK. A delayed pharyngeal response is commonly observed during chew-swallowing. Liquids, solids, and two-phase mixtures exhibit independent timings of pharyngeal swallow initiation.

The interactions between different tastes on initiation of reflex swallow elicited by electrical stimulation in humans.

The act of eating is a source of pleasure for people and is a major factor in maintaining a good quality of life. Several types of products for dysphagia patients are available to decrease aspiration of food that often accompanies daily food intake. The final goal of these products is to improve the ease of forming a food bolus and/or the safety of the swallowing process; however, tastes of products are not a major concern with initiation of swallowing. In the present study, we investigated the effect of bitter taste stimuli (quinine) and the combination of quinine and umami (monosodium glutamate: MSG) applied to the oropharynx on reflex swallows evoked by electrical stimulation to the oropharyngeal mucosa. Each of the distilled water (DW), quinine and quinine-MSG mixture solution (volume of each solutions, 100µl) was applied 1s prior to electrical stimulation. No swallow was evoked when each of the solutions was applied without electrical stimulation. The application of DW and lower concentration of quinine (<100µM) did not affect the latency of reflex swallow, but 100µM quinine application increased the latency of the reflex swallow. In addition, application of quinine-MSG mixture solution counteracted the increase in latency induced by quinine application alone. These findings suggest that MSG enhances the initiation of swallowing along with its well-known increase in appetite stimulation. Adding MSG might be effective when creating food to promote swallowing.

Videofluoroscopic Predictors of Penetration–Aspiration in Parkinson’s Disease Patients

Parkinson's disease (PD) patients show a high prevalence of swallowing disorders and tracheal aspiration of food. The videofluoroscopic study of swallowing (VFSS) allows clinicians to visualize the visuoperceptual and temporal parameters associated with swallowing disorders in an attempt to predict aspiration risk. However, this subject remains understudied in PD populations. Our aim was to identify the predictors of penetration-aspiration in PD patients using the VFSS. Consecutive patients were evaluated using VFSS with different consistencies and volumes of food. A speech-language pathologist measured the type of intra-oral bolus organization, loss of bolus control, bolus location at the initiation of the pharyngeal swallow, the presence of multiple swallows, piecemeal deglutition, bolus residue in the pharyngeal recesses and temporal measures. Scores≥3 on the penetration-aspiration scale (PAS) indicated the occurrence of penetration-aspiration. Using logistic marginal regression, we found that residue in the vallecula, residue in the upper esophageal sphincter and piecemeal deglutition were associated with penetration-aspiration (odds ratio (OR)=4.09, 2.87 and 3.83; P=0.0040, 0.0071 and 0.0009, respectively). Penetration/aspiration occurred only with fluids (both of thin and thick consistency), and no significant differences were observed between fluid types or food volumes. The mechanisms underlying dysphagia and penetration/aspiration in PD patients and indications for further studies are discussed.

Peripheral and central control of swallowing initiation in healthy humans

We investigated (1) how peripheral inputs might assist central inputs in the control of voluntary evoked swallowing, (2) inter-individual variation in involuntary and voluntary swallowing initiation, and (3) whether natural chewing behavior affects the initiation of involuntary swallowing in healthy humans. Eleven participants completed a repetitive saliva swallowing test (RSST), chewing test (CHEW), and rest period (REST). In RSST, participants repetitively swallowed as quickly as possible. In CHEW, subjects chewed gum freely. We delivered pharyngeal electrical stimulation (PEStim) to the laryngopharynx and compared the number of swallows that occurred with and without PEStim. PEStim significantly increased the number of voluntary evoked swallows in RSST, as well as the number of swallows in CHEW and REST trials, although this facilitatory effect was larger in REST trials. We found a positive correlation between the number of swallows at RSST without PEStim and that at REST with PEStim within individuals. Additionally, we found a significant positive correlation between the number of swallows at RSST with PEStim and the sum of that at RSST without PEStim and at REST with PES. Based on the current results, we suggest that (1) peripheral inputs within a certain range appear to facilitate the central inputs that control voluntary swallowing, (2) inter-individual variations in swallowing initiation may arise from differences in the excitability of the common neural network in the lower brainstem, and (3) during chewing, food reduction in the oral cavity is prioritized, such that the neural network associated with chewing may regulate swallowing initiation.