Pharyngeal Phase Of Swallowing Research Articles

Videofluoroscopic evaluation of HIV/AIDS patients with swallowing dysfunction.

We investigated the association of abnormalities of the swallowing mechanism in the oral and pharyngeal phases of swallowing with symptoms of dysphagia and painful swallowing in patients with human immunodeficiency virus (HIV). Seventeen patients, two with HIV and 15 with acquired immunodeficiency syndrome (AIDS), with symptoms of dysphagia or pain on swallowing for routine barium esophagograms were studied prospectively by videofluoroscopic examination of the oropharynx in addition to a routine biphasic esophagogram. The videofluoroscopic studies were performed in conjunction with a speech pathologist. All 17 patients demonstrated abnormalities in the oral, pharyngeal, or esophageal phase of swallowing. Eight patients aspirated, six of whom did not exhibit a cough reflex and were classified as silent aspirators. Seven of the eight patients who aspirated had chest radiographs consistent with aspiration pneumonia. A significant number of HIV-positive and AIDS patients with dysphagia or pain on swallowing have dysfunction of the swallowing mechanism and are at risk for aspiration.

Activity of neurons in ventrolateral respiratory groups during swallowing in decerebrate rats

To elucidate the neuronal basis of the coordination between swallowing and respiration, we examined the swallowing-related activity of respiratory neurons in the ventrolateral respiratory groups of the medulla oblongata of decerebrate, paralyzed and artificially ventilated rats ( n=14). Extracellular recording was made during fictive swallowing evoked by the electrical stimulation of the superior laryngeal nerve from a total of 141 neurons with respiratory rhythm (99 expiratory and 42 inspiratory neurons). The burst of discharge by the hypoglossal nerve was used to monitor the pharyngeal phase of swallowing. The decrementing-expiratory (E-DEC) neurons ( n=62) were activated during ( n=46) or after ( n=10) the hypoglossal bursts, or showed no swallowing-related activity ( n=6). All of the augmenting-expiratory (E-AUG) neurons ( n=37) were silent during the hypoglossal bursts but were activated after each swallow. Inspiratory neurons showed either no swallowing-related bursts ( n=27), or were activated after the hypoglossal bursts ( n=15). Activation of the majority of E-DEC neurons may be related to the arrest of respiration during swallowing, and the post-swallow activation of E-AUG neurons may correspond to the expiratory phase that follows swallowing. We suggest that these behaviors of expiratory neurons are essential in the phase resetting of the respiratory cycle in association with the swallowing.

Motor dysfunction of the upper digestive tract in Pierre Robin sequence as assessed by sucking-swallowing electromyography and esophageal manometry

Objectives: To evaluate motor dysfunction in infants with Pierre Robin sequence (PRS) who manifest upper airway obstruction and congenital dysphagia. Study design: Term infants (n = 28) with nonsyndromic PRS were studied between days 15 and 45. Sucking-swallowing electromyography was used to evaluate suction and coordination between the oral and pharyngeal phases of swallowing. Esophageal manometry was used to study the lower esophageal sphincter, esophageal body, and upper esophageal sphincter functions. Manometry results were compared with those of 16 infants with gastroesophageal reflux disease (GERD). Results: Electromyography showed incoordination of sucking and swallowing in 24 of 28 patients. The disorder was mild in 6, moderate in 6, and severe in 12 patients. All patients showed manometry disturbances: incomplete or asynchronous lower sphincter relaxation (15), multipeaked esophageal body waves (17), very high amplitude waves (14), and asynchronous upper sphincter relaxation (19). The frequency of disturbances and mean resting pressures of both lower and upper sphincters were significantly higher than GERD patients. Conclusion: In Pierre Robin sequence, sucking-swallowing electromyography and esophageal manometry reveal dysfunction in the motor organization of the tongue, the pharynx, and the esophagus. (J Pediatr 2002;140:719-23)

Central integration of swallow and airway- protective reflexes

The relationship between the timing of respiration and swallowing has been proven not to be random. Using pseudorabies virus (PRV) as a transsynaptic neural tracer, a basis for the central integration of swallowing and airway-protective reflexes can be located in the neural circuits projecting to swallowing-related muscles. The premotor neurons (PMNs) that constitute the swallowing central pattern generators, interneuronal networks able to initiate repetitive rhythmic muscle activity independent of sensory feedback, connect with multiple areas of the brainstem and other areas of the central nervous system. Those PMNs that project to muscles used in swallowing have been localized within the nucleus of the solitary tract (NTS) and its adjacent reticular formation, and they are synaptically linked both to peripheral afferents and to cortical swallowing areas. Bartha PRV, an attenuated vaccine strain of swine α-herpesvirus with a long postinjection survival rate and the ability to produce controlled infections that spread in a hierarchical manner within synaptically linked neurons, can specifically label neurons projecting to PMNs of a given circuit. Thus, it has been used to isolate two neuroanatomically distinct subnetworks of PMNs involved in the buccopharyngeal and esophageal phases of swallowing. Use of PRV as a neural tracer shows that during the buccopharyngeal phase of swallowing, vagal afferents from the pharynx and larynx and from the superior laryngeal nerve terminate in the intermediate and interstitial subnuclei of the NTS. Motoneurons projecting to the pharynx and larynx are located in the semicompact and loose formations of the nucleus ambiguus (NA). Neural tracing with PRV also shows that esophageal PMNs have direct synaptic contact with esophageal motoneurons in the compact formation of the NA. Moreover, esophageal PMNs are localized exclusively to the central subnucleus of the NTS, a site that also is the sole point of termination of esophageal vagal afferents. Using PRV, one can identify third-order (neurons projecting to PMNs) esophageal neurons in sites where pharyngeal PMNs have been noted. Injection of PRV into the esophagus and subsequent detection using immunofluorescence found a subpopulation of neurons in the intermediate and interstitial subnuclei of the NTS. This subpopulation projects to pharyngeal motoneurons and buccopharyngeal PMNs, and it is synaptically linked to esophageal PMNs. The synaptic link between buccopharyngeal and esophageal PMNs provides a potential anatomic substrate within the NTS for the central integration of esophageal peristalsis with the pharyngeal phase of swallowing and airway-protective reflexes. Human studies and animal models investigating esophagoglottal closure and pharyngo–upper esophageal sphincter (pharyngo-UES) contractile reflexes have located the neural pathways that mediate airway-protective reflexes. Similar studies and models using two PRV strains injected simultaneously into different swallowing and respiration-related muscle groups may identify synaptic connectivity between laryngeal, esophageal, and pharyngeal PMNs and, thus, may help to demonstrate the central integration of swallowing and airway-protective reflexes.

Swallowing Dysfunction Related to Snoring: A Videoradiographic Study

Biopsy studies of the soft palatal and oropharyngeal tissues in habitual snorers and patients suffering from obstructive sleep apnoea have shown signs of neurogenic lesions. These lesions might affect the pharyngeal swallowing function, which is dependent on adequate sensitivity. The objective of the present study was to test the hypothesis that snoring is associated with aberrant pharyngeal swallowing function. Forty-one consecutive patients without dysphagia, seeking medical attention because of heavy snoring and various degrees of daytime sleepiness, were prospectively selected. Fifteen non-snoring volunteers without dysphagia served as controls. Patients and volunteers were videoradiographically examined in lateral and posteroanterior views during the oral and pharyngeal phases of swallowing. The hypothesis was verified. Snoring patients demonstrated deviant pharyngeal swallowing function seven times more frequently than did the non-snoring volunteers. Deviant pharyngeal swallowing function was observed in 22 (54%) of the snorers compared with 1 (7%) of the non-snoring volunteers. Impaired bolus control with premature leakage of bolus into the pharynx and a delayed evocation of the swallowing reflex was the most common finding, followed by bolus residual in the pharynx and laryngeal penetration. The conclusion was that snoring is associated with subclinical pharyngeal swallowing dysfunction.

Laryngeal penetration: a predictor of aspiration in infants?

We routinely observed "isolated" laryngeal penetration (ILP) on upper GI studies in infants with no risk for aspiration. To determine whether "isolated" LP (LP during the pharyngeal phase of swallowing) is a benign process in infants and therefore not a predictor of aspiration as it is known to be in adults. Two radiologists retrospectively reviewed videotaped upper GI studies done over a 2-year period on patients less than 2 years of age. A total of 110 studies was reviewed, which produced a study group of 34 patients who had no history or clinical suspicion for swallowing dysfunction. Of the 34 patients in the group, 33 demonstrated ILP without radiographic or clinical evidence of aspiration. ILP is a benign, normal process in infants likely due to immaturity of the swallowing mechanism. It is not a reliable predictor of aspiration as it is in adults.

Fundamentals of neurogastroenterology

Current concepts and basic principles of neurogastroenterology in relation to functional gastrointestinal disorders are reviewed. Neurogastroenterology is emphasized as a new and advancing subspecialty of clinical gastroenterology and digestive science....

Muscular compliance of the auditory tube

The simultaneous electromyographical assessment of innervation patterns of the mylohyoid and the tensor veli palatini muscle is introduced as a new technique for the examination of the auditory tube function. Clinical studies were performed on 30 healthy volunteers and 50 patients suffering from chronic tubotympanic mucositis and cholesteatoma. Concentric needle electrodes were advanced into the tensor veli palatini muscle through the palate. The mylohyoid muscle was examined using surface electrodes. Innervation patterns of the tensor veli palatini muscle in volunteers were limited to the time interval of the mylohyoid innervation pattern only, i.e., the oral and pharyngeal phases of swallowing. In 14 of the chronic otitis patients these tensor muscle innervation patterns were found outside this interval. This observation provides a new pathophysiological explanation for the clinical concept of a relative closing failure of the auditory tube. These results emphasize the significance of coordination in muscular compliance of the tube.

Swallowing is a precarious business

See article on page537 The upper oesophageal sphincter (UOS) remains closed at rest as a result of a combination of intrinsic muscle tone and passive pressure from the anterior mass...

Solitarial premotor neuron projections to the rat esophagus and pharynx: Implications for control of swallowing

Background & Aims: The buccopharyngeal and esophageal phases of swallowing are controlled by distinct networks of premotor neurons localized in the nucleus tractus solitarius. The neuronal circuitry coordinating the two phases was investigated using a combination of central and peripheral tracing techniques. Methods: Using pseudorabies virus, a transsynaptic tracer, in anesthetized rats, third-order esophageal neurons (neurons projecting to premotor neurons) were identified. In a separate protocol that combined transsynaptic and retrograde fluorescent tracing, third-order esophageal neurons projecting to pharyngeal motoneurons (buccopharyngeal premotor neurons) were then identified. Results: Third-order esophageal neurons were identified in the interstitial and intermediate subnuclei of the nucleus tractus solitarius and in other medullary, pontine, midbrain, and forebrain nuclei. A subpopulation of these neurons (double labeled) in the interstitial and intermediate subnuclei were found to project to pharyngeal motoneurons (buccopharyngeal premotor neurons) and to be linked synaptically to esophageal premotor neurons. Conclusions: The synaptic link between buccopharyngeal and esophageal premotor neurons provides an anatomic pathway for the central initiation of esophageal peristalsis and its coordination with the pharyngeal phase of swallowing. This neural circuitry within the nucleus tractus solitarius is consistent with a complex central control mechanism for the swallowing motor sequence that can function independently of afferent feedback. GASTROENTEROLOGY 1998;114:1268-1275

Comments on selected recent dysphagia literature

Hamdy et al. note, ‘‘Oropharyngeal dysphagia occurs in up to a third of patients presenting with a unilateral hemiplegic stroke, yet its neurophysiological basis remains unknown.’’ They continue, ‘‘Animal data indicate that stimulation of either cortical hemisphere can initiate swallowing, which suggests that dysphagia after a stroke is due to damage either to both hemispheres or to the brainstem swallowing centre. However, neuropathological examination of dysphagic stroke patients either at necropsy or with magnetic resonance imaging has shown that, in many cases, the lesion is discrete and unilateral.’’ The authors previously reported on the use of transcranial magneto-electric stimulation (TCMS) to identify the corticofugal projections to the muscles of swallowing [1]. They found ‘‘that oral muscles, such as the mylohyoids are represented symmetrically between the two hemispheres, whereas muscles of the pharynx and oesophagus are represented very asymmetrically, with most individuals having a dominant swallowing hemisphere, independent of handedness.’’ Based on these earlier findings, Hamdy et al. generated ‘‘two hypotheses to explain why a unilateral hemispheric stroke might cause oropharyngeal dysphagia.’’ They state, ‘‘First, innervation of the brainstem by both hemispheric centres might be required to initiate swallowing, so destruction of either would leave inadequate cortical function to evoke normal swallowing. . . . Alternatively, since there is functional asymmetry between the two hemispheres for pharyngeal function, oropharyngeal dysphagia would result from damage to the hemisphere where the dominant pharyngeal centre was located. This second hypothesis would also predict that swallowing should remain normal if the dominant centre for pharyngeal function was present on the unaffected hemisphere.’’ The authors recruited 20 patients with unilateral hemiplegic stroke within the previous 6 weeks. Patients underwent the following evaluations: (1) clinical examination by a speech and language therapist using a standardized bedside assessment, (2) standardized neurological assessment, (3) submental electromyography (EMG) of mylohyoid muscles, (4) pharyngeal EMG via an intraluminal catheter positioned with manometric guidance, (5) EMG of muscles of the thenar eminence (muscles that have contralateral but symmetrical hemispheric representation), and (6) an experimental protocol using TCMS to determine excitability thresholds and motor-evoked response amplitudes and latencies. Eight of the 20 patients had oropharyngeal dysphagia, and the other 12 patients swallowed normally. Computed tomography of the brain revealed that 4 of the dysphagic patients had right hemisphere infarcts and 4 had left hemisphere infarcts. Six of the nondysphagic patients had right hemisphere infarcts, and 6 had left hemisphere infarcts. Hamdy et al. report, ‘‘Our study has shown that patients dysphagic after unilateral hemisphere stroke have smaller pharyngeal responses from the unaffected hemisphere than do non-dysphagic patients, irrespective of the side and level (cortical or subcortical) of the lesion. . . . One possible explanation for this difference is that the smaller responses are a reflection of the asymmetrical motor representation of pharyngeal function on the cerebral cortex. In other words, with damage to the hemisphere containing the predominant pharyngeal centre, swallowing cannot be maintained by the smaller pharyngeal centre in the unaffected hemisphere.’’ The authors continue, ‘‘The similarity in mylohyoid responses between dysphagic and non-dysphagic stroke patients is consistent both with our observation that the dysphagic patients had predominantly pharyngeal swallowing problems, and the fact that the pharyngeal phase of swallowing is the most important clinical determinant of aspiration in stroke populations. Furthermore, . . . our findings suggest that the cortical control of Dysphagia 13:116–120 (1998)

Laryngeal electromyography for the diagnosis and management of swallowing disorders.

Laryngeal electromyography has proved useful for the evaluation of neurologic disorders of the larynx. The techniques for this procedure are also well suited to investigate disorders of the pharyngeal phase of swallowing. The responses from the thyroarytenoid muscles, the cricothyroid muscles, and the cricopharyngeus muscle can offer information to aid in the diagnosis, prognosis, and in some cases, treatment of dysphagia. A general review of electromyographic responses with sample tracings from the larynx are included in this article.

Laryngeal electromyography for the diagnosis and management of swallowing disorders

Laryngeal electromyography has proved useful for the evaluation of neurologic disorders of the larynx. The techniques for this procedure are also well suited to investigate disorders of the pharyngeal phase of swallowing. The responses from the thyroarytenoid muscles, the cricothyroid muscles, and the cricopharyngeus muscle can offer information to aid in the diagnosis, prognosis, and in some cases, treatment of dysphagia. A general review of electromyographic responses with sample tracings from the larynx are included in this article. (Otolaryngol Head Neck Surg 1997;116:344-8.)

Videofluoroscopic evaluation of dysphagia in motor neurone disease with modified barium swallow.

The role of videofluoroscopy with the modified barium swallow in the assessment and management of motor neurone disease (MND) is discussed. Nine patients (age range 40-82) with dysphagia secondary to MND were assessed over a four-year period. The examinations were carried out by a multiprofessional team of radiologist, speech and language therapist and dietitian assessing the preoral, oral and pharyngeal phases of swallowing. Preoral feeding abnormalities were present in four out of nine patients, oral phase abnormalities in eight out of nine patients, while 33% of patients demonstrated abnormality in all three phases. Where aspiration occurred (four out of nine cases), no cough reflex was noted. On the basis of these examinations management changes were introduced in all patients. Nonoral feeding was continued or introduced in three patients. Videofluoroscopic examination with the modified barium swallow may be helpful in planning suitable feeding regimes for dysphagia in MND.

Kinematic and Dynamic Characteristics of Solid Pellet Movement during the Pharyngeal Phase of Swallowing

Information on solid particle movement through the pharynx, in addition to its physiologic importance, has relevance to the swallowing of medications in pill form. The purpose of this study was to determine the kinematics of a solid particle during the oral-pharyngeal phase of swallowing. We used a concurrent manometric-videofluoroscopic technique and identified two distinct zones of increasing bolus velocity, one at the tongue base and the other at the pharyngo-upper esophageal sphincter (UES) region. Velocity decreased significantly (p < .05), to 9.0 +/- 1.0 cm/s, while the bolus traversed the area located between the tip of the horizontal epiglottis and the pharyngeal wall. The velocity of the liquid barium bolus head was similar to that of the solid barium pellet. The average bolus tail velocity was relatively constant. The acceleration of the barium pellet was temporally associated with development of an incrementally decreasing pressure distal to the location of the pellet in the hypopharynx and across the UES. In conclusion, the kinematics of a solid particle are similar to those of the head of a liquid bolus, but both are different from bolus tail kinematics. During the pharyngeal phase of swallowing, the area located ahead of the bolus exhibits an incrementally decreasing pressure, caudally. This may facilitate bolus transport and contribute to airway protection.

Age Effects on Lingual Pressure Generation as a Risk Factor for Dysphagia

Tongue activity plays a crucial role in both oral and pharyngeal phases of swallowing. In this study, maximum lingual isometric and swallowing pressures were quantified in two groups of healthy men to investigate possible age effects on performance. Magnetic resonance images of the brain were also obtained to examine the relationship between age-related anatomical changes and swallowing function. Pressures were recorded at three lingual sites (tip, blade, and dorsum) during a maximal isometric task and during saliva swallows. Task order was randomized, and subjects performed three trails per placement site. Additionally, t2-weighted MRIs were obtained on 9 of the 10 young subjects (mean age = 25 years) and all 15 older subjects (mean age = 75 years). Maximal isometric pressures were significantly greater for younger subjects at the tongue blade site (p = .002), whereas peak swallowing pressures remained similar across both age groups. Within-subject comparisons of maximum isometric to swallowing pressures, a measure of reserve capacity, revealed reduced difference scores at the tongue blade in the older group (p = .02). Older subjects exhibited significantly more cerebral atrophy (p = .001) and greater incidence of periventricular white matter lesions (p = .0001) than did younger subjects. While swallowing pressures remain similar across the life span, overall pressure reserve declines with age. The implications are: (a) older people may be working harder to produce adequate swallowing pressures, and (b) age-related illness may put geriatric patients at higher risk for dysphagia, thus further complicating recovery.

Influence of aging on oral-pharyngeal bolus transit and clearance during swallowing: scintigraphic study

The aim of the study was to determine the influence of normal aging on regional transit and the efficiency of bolus clearance during the oral and pharyngeal phases of swallowing. We compared scintigraphically derived oral-pharyngeal transit times and isotope clearance during swallowing in 21 healthy aged volunteers (mean age 68 +/- 8 yr) and 9 young controls (mean age 28 +/- 7.5 yr). Subjects swallowed 5- and 10-ml water boluses mixed with 30 MBq 99mtechnetium tin colloid. Oral and pharyngeal transit times, pharyngeal clearance time, and postswallow residual counts in each region were derived from time-activity curves. Pharyngeal residual counts were significantly greater in the aged than in controls (P = 0.0008), but age did not influence oral residual. Aging significantly prolonged oral transit time (P = 0.02), pharyngeal transit time (P = 0.0004), and pharyngeal clearance time (P = 0.0001). We conclude that normal impairs the efficiency of pharyngeal clearance during swallowing, prolongs scintigraphic measures of oral-pharyngeal transit, and increases the exposure time of the glottis to the swallowed bolus.

Secondary microvascular tongue reconstruction: functional results.

Between 1978 and 1991, 56 microvascular composite flaps were used for oromandibular reconstructions: 15 for primary total and subtotal tongue reconstruction and five for secondary major tongue reconstruction. The delayed reconstructions were performed to improve the oral and pharyngeal phases of swallowing. Using a floor of the mouth composite bone grafting technique to reposition the tongue and obliterate the oral dead space intraoral food transport was improved (three of five patients), but aspiration persisted (three of four patients). When compared with 10 patients evaluated for primary total and subtotal tongue reconstruction the primary reconstruction group showed superior swallowing (eight dynamic oral transport, no aspiration) and speech results. The poor results of secondary reconstruction are attributed to scarring and irreversible damage to remaining functional muscles involved in protecting the laryngeal aditus.

Videofluoroscopy in the assessment of feeding disorders of children with neurological problems.

A multidisciplinary assessment, including videofluoroscopy, was carried out on 14 children with feeding difficulties associated with neurological problems. Recommendations were made on all aspects of feeding and the trunk position was changed for half of the patients. A later interview with the parents confirmed that the recommendations had been helpful. The optimum trunk position for feeding was determined during videofluoroscopy by positioning the patient in the erect or reclined position, and also by analysis of relative difficulties during the oral and pharyngeal phases of swallowing. Those with difficulties mainly in the oral phase fed best in the reclined position; those with difficulties mainly in the pharyngeal phase fed best in the erect position, particularly if they had upper-oesophageal sphincter spasm in association with a tonic labyrinthine reflex.

Evaluation, treatment, and follow‐up results of post polio patients with dysphagia

Twenty consecutive patients were evaluated for reports of dysphagia from post-polio clinics. Only half the patients reported a history of swallowing problems at the time of their acute poliomyelitis. Each patient received a videofluorographic evaluation of the oral and pharyngeal phases of swallowing, and then was provided with recommendations to improve swallowing skills. A follow-up questionnaire was sent to all patients. The respondents had an average interval of 12 months since the initial evaluation. Of the 18 patients responding to the questionnaire, 14 (77%) reported regular use of the swallowing suggestions. Comparison of pre-evaluation results to followup of the 18 respondents yielded a statistically significant decline in the frequency of choking (p = 0.0156) and food sticking in the throat (p = 0.0195). We conclude that a dysphagia program can result in significant improvement of the swallowing symptoms reported with the post-polio population.