Pharyngeal Stage Of Swallowing Research Articles

Firing characteristics of swallowing interneurons in the dorsal medulla during physiologically induced swallowing in perfused brainstem preparation in rats

Oropharyngeal swallowing is centrally mediated by a swallowing central pattern generator (Sw-CPG) in the medulla oblongata. The activity of the Sw-CPG depends on the sensory inputs determined by physical and chemical bolus properties. Here we investigate the sensory-motor integration during swallowing arising from different sensory sources. To do so we electrically stimulated the superior laryngeal nerve and we triggered swallowing with oral injections of distilled water or capsaicin solution and extracellularly recorded from swallowing interneurons in arterially perfused brainstem preparations of rats. We recorded the activities of 40 neurons, while monitoring the motor activities of the phrenic, vagal and hypoglossal nerves. Eighteen neurons responded to electrical stimulation of the ipsilateral superior laryngeal nerve, and 6 neurons were excited by oral fluid injection, while 16 non-respiratory neurons did not receive afferent inputs to either electrical or physiological stimuli. The cellular activities displayed by swallowing interneurons during electrical and physiological stimulation of pharyngeal and laryngeal afferent input reveal complex adaptations of the timing of firing patterns and frequencies. The modulation of neuronal activity is likely to contribute to the coordination of efficient bolus transfer during the pharyngeal stage of swallowing.

Videofluoroscopic Study of Swallowing Disorders in Patients with Parkinsonism

Background: Dysphagia in Parkinsonism is often reported, and diagnosed, late. This can be a contributor to morbidity and mortality. Hence, a screening tool is essential as part of routine workup of these patients. The gold standard diagnostic modality for dysphagia is Videofluoroscopic Swallowing Study (VFSS). However, being an interventional imaging procedure, it cannot be made routine for every case. Aim: To study swallowing problems in patients with Parkinsonism using a screening questionnaire and to objectively observe the findings at VFSS in these patients. Materials and Methods: Fifteen patients (nine males and six females) attending the Parkinsonism clinic over a period of 1 year, and meeting the inclusion criteria, were included in the study. After standard neurological evaluation, they were administered our screening tool, the Amrita Dysphagia Screening Questionnaire (ADSQ). Next, they underwent VFSS. The scores and findings from these were documented, and the results were tabulated. Results: The average Hoehn and Yahr scale and ADSQ scores were 0.488 and 0.799, respectively. Mean age was 68.9 years. In VFSS, all the patients showed features of oropharyngeal swallowing disorders characteristic of Parkinsonism. These included features of bradykinesia such as tongue pumping, smaller tongue movements and piecemeal deglutition in the oral preparatory stage of swallowing, and reduced pharyngeal constriction, premature spillage, vallecular and pyriform sinuses residue, reduced hyoid movement, prolonged transit time, delayed laryngeal closure, aspiration/penetration, and repetitive or multiple swallow in the pharyngeal stage of swallowing. Conclusion: The present study has documented the objective findings of swallowing disorders, especially of the oral phase, in patients with Parkinsonism. This, along with our screening tool, must be considered essential in the management protocol for this debilitating neurological condition.

Surgical treatment of enterovirus D68 brainstem encephalitis-induced dysphagia

Cluster of acute flaccid paralysis and cranial nerve dysfunction was associated with a 2014 outbreak of enterovirus D68 (EV-D68) respiratory illness in US. We describe a 33 year-old male patient of refractory dysphagia due to EV-D68-induced brainstem encephalitis successfully treated by surgery. Following acute upper respiratory tract infection, he developed dysphagia and bilateral facial paralysis. A coughing reflex was readily produced when the laryngopharyngeal fiberscope touched the epiglottis, however, water infusion induced only very weak and slow swallowing reflex, suggesting that only motor component was impaired but sensory function was preserved during swallowing. Despite eight months-conservative rehabilitations, Food Intake Level Scale (FILS) remained level 4. Therefore, corrective surgeries including cricopharyngeal myotomy, laryngeal suspension, and pharyngeal flap were performed. Thirty-six days after surgery, FILS rapidly and dramatically improved to level 8. This is the first report describing a successful surgical intervention for EV-D68-induced refractory dysphagia. Surgical treatment was suitable for EV-D68-induced dysphagia, perhaps because sensory function was preserved and only motor disturbance was present during the pharyngeal stage of swallowing.

Flow properties of oral contrast medium formulations depend on the temperature

During the therapeutic videofluoroscopic examination of swallowing, gradation of bolus volume, texture, and viscosity can be implemented to determine the optimal bolus characteristics in that particular patient. When a thickened liquid is given to a dysphagic patient it is served at room temperature. However, in these patients with a delayed oral and/or pharyngeal stage of swallow, the bolus is held for a long time in the oral cavity. The temperature of the thickened liquid thereby increases. To study the rheological exploration (variation of viscosity with temperature) of thickened food used for radiologic swallowing examinations in patients with oral and pharyngeal dysfunction, in particular in mixtures of barium sulfate suspensions and in iodine solutions. Deep-frozen mango purée was thawed at room temperature. It was then mixed with barium sulfate contrast medium to a density of 25% w/w. Resorce Thicken Up was mixed at room temperature at two concentrations: 4.3% w/w (4.5 g thickener + 100 g distilled water) and 6.0% w/w (4.5 g thickener + 70 g distilled water). The thickener consisted of modified corn starch. Resorce Thicken Up was also mixed at room temperature with two concentrations of an iodine contrast material, iohexol (Omnipaque, 350 mg I/ml). The two concentrations were: 4.3% w/w (4.5 g thickener + 100 g iohexol) and 6% w/w (6 g thickener + 100 g iohexol). Measurements were carried out from 20 degrees C to 37 degrees C using a Stresstech HR rheometer. The rheometer was equipped with a concentric cylinder measuring system (inner cylinder 15 mm). The samples containing thickener in water as well as in iohexol showed a dependence on thickener concentration and temperature. The mango purée with barium sulfate displayed very small temperature dependence. The thickener solutions in iohexol had significantly higher viscosity compared with the other thickener solutions and the mango purée. The relative decrease shows that mango purée, the 6% thickener solution in water, and solutions with iohexol exhibited similar relative viscosity change at different temperatures. Our conclusion is therefore that it is important always to make the solution with high precision. It is also of importance to observe how long the patient keeps the bolus in the mouth. This might vary and actually it may not be possible to influence this factor. When different types of thickeners are compared, it is important to take into account the temperature at which the thickener is observed.

Identification of swallowing cortex by means of magnetoencephalography in the normal human

Problem: Swallowing is a complex motor sequence; it is initiated voluntarily by the act of assumed cerebral cortex, and is subsequently evoked by peripheral inputs to the brainstem essentially in the pharyngeal stage. Little is known about the mechanism of transition from cortical initiation to pharyngeal reflexogenic stage of swallowing, and about the swallowing representation of the cerebral cortex and its functional role in pharyngeal swallowing. Methods: Studies were performed in 6 healthy adult volunteers. Electromyographic (EMG) activity of the thyrohyoid (TH) muscle was recorded with platinum bipolar hooked wire electrodes as an indicator for pharyngeal swallowing. Magnetoencephalographic (MEG) were measured by means of 37 channel SQUID and averaged 32 to 128 times that of swallowing in each subject with the reference of the TH EMG onset. The origin of the current dipole related to the pharyngeal swallowing was calculated and localized in the cerebral surface. Results: Calculated equivalent current dipoles related to the oropharyngeal swallowing were observed 50 to 100 msec prior to the TH EMG onset, which lasted until the pharyngeal stage of swallowing. These dipoles were located around the opercum adjacent to the insula on the superimposed MR images. After the surface application of 1 to 2 mL of 4% lidocaine to pharyngo-laryngeal mucosa, those current dipoles could not be identified anymore. Conclusion: Swallowing-related cortex located in and around the opercum not only initiates oral stage of swallowing, but significantly affects the triggering of pharyngeal swallowing. Significance: The results of this study give us a unique understanding of oropharyngeal dysphagia caused by lesion of the swallowing-related cortex and its descending pathway to the brainstem. Applying MEG study to clinical cases may provide a new aspect of pathophysiology in dysphagia. Support: None reported.

Videofluorography of the Pharynx in Patients, Sutffcring from Aspiration Pneumonia

We evaluated videofluorographic recordings of the pharynx (VF) in patients suffering from aspiration pneumonia. The patients consisted of 55 men and 6 women who consulted the ENT Department at Kumamoto University Hospital between May 1994 and February 2002. Surgery for an upper alimentary tract malignancy (16 patients) was the most frequent background feature. The number of patients with cerebrovasucular disease and neuronal/neuromuscular diseases were 11 and 12, respectively. VF enabled the misswallowing of barium into the trachea to be visualized in 38 patients. Of these 38 patients, 20 exhibited misswallowing during or after the pharyngeal stage of swallowing. Among the 23 patients in whom misswallowing was not detected, 13 had upper alimentary tract diseases. The VF findings suggested the presence of gastroesophageal clearance after swallowing. Gastro-esophageal regurgitation may be a significant factor, in addition to the silent aspiration of oral and pharyngeal secretions during the night as a trigger of recurrent aspiration pneumonia.

Coordination of Laryngeal Movements and Orofacial Muscle Activities in Swallowing.

The purpose of the present study was to investigate the coordination between the muscle activities of the masticatory, facial and suprahyoid muscles, and the action of the oral, pharyngeal and laryngeal organs in healthy subjects during chewing and swallowing barium bread. Videofluorography (VF) and electromyography (EMG) were recorded while subjects took in, masticated and swallowed the barium bread.The following results were obtained: in the pharyngeal stage of swallowing, a monophasic wave was observed during laryngeal movement. The reproducibility was confirmed in the relationship between the laryngeal movement wave and bolus position when swallowing. The duration of muscle activity in the masticatory muscles, orbicular oris muscle and suprahyoid muscle during swallowing was significantly longer than in chewing. In the temporal relationship between laryngeal movement and muscle activities, the temporal and masseter muscles began the activities before the onset of the monophasic laryngeal movement, whereas the digastric and mylohyoid muscles were activat-ed almost simultaneously or slightly after onset.

FEESST: a new bedside endoscopic test of the motor and sensory components of swallowing.

We here introduce an office or bedside method of evaluating both the motor and sensory components of swallowing, called fiberoptic endoscopic evaluation of swallowing with sensory testing (FEESST). FEESST combines the established endoscopic evaluation of swallowing with a technique that determines laryngopharyngeal (LP) sensory discrimination thresholds by endoscopically delivering air pulse stimuli to the mucosa innervated by the superior laryngeal nerve. Endoscopic assessment of LP sensory capacity followed by endoscopic visualization of deglutition was prospectively performed 148 times on 133 patients with dysphagia over an 8-month period. The patients had a variety of underlying diagnoses, with stroke and chronic neurologic disease predominating (n = 94). Subsequent to LP sensory testing, a complete dysphagia evaluation was conducted. Various food and liquid consistencies were dyed green, and attention was paid to their management throughout the pharyngeal stage of swallowing. Evidence of latent swallow initiation, pharyngeal pooling and/or residue, laryngeal penetration, laryngeal aspiration, and/or reflux was noted. Recommendations for therapeutic intervention were based on information obtained during the FEESST and often involved the employment of compensatory swallowing strategies, modification of the diet or its presentation, placement on non-oral feeding status, and/or referral to other related specialists. All patients successfully completed the examination. In 111 of the evaluations (75%), severe (>6.0 mm Hg air pulse pressure [APP]) unilateral or bilateral LP sensory deficits were found. With puree consistencies, 31% of evaluations with severe deficits, compared to 5% of evaluations with either normal sensitivity or moderate (4.0 to 6.0 mm Hg APP) LP sensory deficits, displayed aspiration (p < .001, chi2 test). With puree consistencies, 69% of evaluations with severe deficits, compared to 24% with normal or moderate deficits, displayed laryngeal penetration (p < .001, chi2 test). FEESST allows the clinician to obtain a comprehensive bedside assessment of swallowing that is performed as the initial swallowing evaluation for the patient with dysphagia.

Physiology of oropharyngeal swallow in the cat: a videofluoroscopic and electromyographic study.

The majority of animal studies of deglutition have examined electrically stimulated swallows in sedated animals. This present investigation examined oropharyngeal and cervical esophageal swallow physiology in three awake normal domestic cats using concurrent electromyography (EMG) and videofluorography (VFG). Hooked wire electrodes were surgically implanted into six oropharyngeal muscles in each cat. During collection of VFG and EMG data, each cat ate barium-impregnated cat food while the fluorography tube focused on a lateral view of the oral cavity, pharynx, and cervical esophagus. A number of significant differences in the physiology of swallowing were found between the cat and human adult. The oral stage of swallow is much longer in the cat with bolus accumulation in the valleculae. Duration and components of the pharyngeal stage of swallow are much faster, and the pharyngeal stage occurs earlier in relation to bolus passage through the cricopharyngeus. In addition, the cat exhibits a marked superior constrictor bulge at the onset of the pharyngeal contractile wave and summation of the peristaltic waves in the esophagus, whereas the human adult does not. Feline swallow physiology is more similar to that of the human infant than that of human adults.

Swallowing disorders after traumatic brain injury

This article briefly reviews normal swallowing physiology and the nature of dysphagia in the traumatically brain-injured population. Traumatically brain-injured Individuals may demonstrate oral and pharyngeal stage dysphagia. Typically, more than one abnormality in swallowing is observed. Aspiration can occur before, during, and after the pharyngeal swallow as a result of these swallowing problems. Tongue control for speech and swallowing, and the oral and pharyngeal effects of the tongue during swallowing are compared. Effects of head injury on lingual control for swallowing and speech are different. Oral tongue functioning appears to be a poor predictor of tongue base retraction during the pharyngeal stage of swallowing.

Motions of the posterior pharyngeal wall in swallowing.

The motions of the posterior pharyngeal wall during swallowing were studied in four asymptomatic males using a new method for videoradiography. Radiopaque markers of 4 mm diameter were affixed to the pharyngeal wall by suction. Ventrodorsal and axial components of motion were measured frame by frame. Large axial motions occurred during the pharyngeal stage of swallowing. Cephalad displacement of each marker occurred early and was followed by caudad motion. Within the pharyngoesophageal segment, there were cephalocaudal motions measuring as much as 25 mm. A late caudad motion beyond the reference position was observed in this segment in two participants. This late motion may play a role in passing the bolus through the pharyngoesophageal segment. The findings support the concept of an "engulfment" mechanism in pharyngeal kinesiology.

Swallowing and speech production in Parkinson's disease.

Videofluoroscopy was used to examine movement patterns during swallowing and speech production in 6 parkinsonian subjects and 6 age-matched controls. Motility patterns for liquid and semisolid swallows were documented. We performed temporospatial analyses of oropharyngeal structures, particularly the velum, which is prominently involved in both motor speech production and swallowing. Differences were found between groups and conditions. All of the parkinsonian subjects exhibited abnormal oropharyngeal movement patterns and timing during the volitional oral as well as the pharyngeal stage of swallowing; only 50% of these subjects admitted to any swallowing difficulty upon questioning. Two of the subjects with Parkinson's disease aspirated liquids. Duration of velar movement during speech production significantly differentiated the groups (p less than 0.01), reflecting reduced range of velar motion. Our findings suggest that rigidity and bradykinesia underlie the volitional speech abnormality as well as the disordered oral and pharyngeal stages of swallowing. Findings indicate that parkinsonian patients may be "silent aspirators" with decreased cough reflexes and lack of awareness of aspiration. The clinical value of videofluoroscopic monitoring of swallowing is that aspiration may be detected and managed early.

Pharyngeal Stage of Swallowing

This paper describes dynamics of the pharyngeal, or the second stage of volitional swallowing in normal and pathological conditions. The description is based upon our current investigations as well as upon available literature. In our investigations, simultaneous recordings of EMG of selected swallowing muscles and X-ray video images were adopted.In normal swallowing, a series of events take place consistently with respect to timing during the pharyngeal stage. There is no clear-cut distinction between the oral and the pharyngeal stages in the activities of the pertinent muscles as well as in the movements of the food channel. It seems, however, to be practical to assume that the pharyngeal stage begins roughly with the first appearance of bolus in the pharynx and ends with complete disappearance of bolus from the pharynx in normal swallowing. From the neurological point of view, it turned out that this period corresponds to the period of relaxation of the cricopharyngeal muscle, lasting approximately 0.5sec.Swallowing begins with an elevation of the larynx. Then, the velum and the tongue base begin to rise, the epiglottis to bend backwards, and the supraglottic region to close. Bolus first enters the pharynx when the velopharyngeal closure is about completed. Almost simultaneously with this, the cricopharyngeal muscle relaxes whereas the vocal fold adductors and the thyrohyoid muscle contract. Shortly after, peristaltic movements of the pharynx occur. When bolus is completely transported into the esophagus, the velum and the tongue base begin to fall, the larynx starts opening, and the cricopharyngeal muscle contracts to close the pharyngo-esophageal junction. The entire procedure ends up with a complete fall of the larynx.Even in some pathological conditions, such as amyotrophic lateral sclerosis, oculopharyngeal muscular dystrophy and “cricopharyngeal achalasia, ” the muscles act in the similar fashion as in normal with respect to timing. This causes an incoordination of muscular activities and the passage of bolus. No feedback mechanism or volitional adaptation seems to be able to modify the timing of muscular exertion during the pharyngeal stage.

Topical Anesthesia and Intubation

To the Editor.— Cohen and Levinsky (236:562, 1976) warned that care should be exercised... when food is ingested within 60 minutes following the use of topical anesthetics in the pharynx. They pointed out that orally administered topical anesthetic agents may interfere with the pharyngeal stage of swallowing and lead to aspiration. A similar admonition applies to the use of topical anesthesia before performing an awake orotracheal intubation in an individual with a full stomach. I have witnessed aspiration in a patient whose pharynx and glottis were sprayed with a topical anesthetic prior to intubation with the patient awake. Topical anesthesia should be applied only to the lower lip and the outer half of the tongue prior to performing such orotracheal intubation. Spraying the base of the tongue may inadvertently anesthetize the pharynx and the glottis, particularly if the patient inhales during the spraying.