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PubMed1996

Quantitative assessment of swallowing in healthy adults.

Swallowing has hitherto been evaluated during physical examination, radiologic barium studies, manometry, and cervical auscultation. Radiography principally demonstrates qualitative aspects of oral and pharyngeal function, whereas quantitative aspects have primarily been documented by manometry. To evaluate swallowing quantitatively, without using invasive methods or radiation, we have applied a combined test of water drinking, i.e., the Repetitive Oral Suction Swallow test (ROSS). The test provides reliable measurements of suction pressure, bolus volume, timing of important events in oral and pharyngeal swallow, and respiration. The test is described and results from 292 healthy, non-dysphagic subjects are presented. We found a mean bolus volume of 25.6 +/- 8.5 ml during single swallow and 21.1 +/- 8.2 ml during stress (forced, repetitive swallow). During forced, repetitive swallow, the bolus volume was more strongly associated with suction time (r2 = 0.55) than with peak suction pressure (r2 = 0.04), indicating that suction time is more important than suction pressure in determining the bolus volume. The oral-pharyngeal transit time decreased: single swallow 0.56 +/- 0.36 sec, forced repetitive swallow 0.23 +/- 0.11 sec, as did the coefficient of variation (48% and 64%, respectively) indicating a more automatic neural process for pharyngeal function in forced, repetitive swallow. The postswallow respiration started with inspiration in 10% of studied individuals, but did not correlate with deviations in other variables in the test. Thus, postswallow inspiration must be considered as normal. The ROSS test offers a rapid and easy quantitative assessment of swallowing.

Adolescent↗
PubMed1994

Swallowing in neurological outpatients: use of a timed test.

Swallowing was studied prospectively in a consecutive group of 90 neurology outpatients under 70 years of age. No patient had been referred primarily because of dysphagia. Patients were classified into four groups: those with (1) neurological or (2) non-neurological diagnoses possibly relevant to disordered swallowing, (3) functional disorders, and (4) definite diagnoses not likely to be relevant. They were defined as having abnormal or probably abnormal swallowing if two or more of the following were present: a complaint of swallowing problem, abnormal symptoms or signs, a slow swallowing speed (< 10 ml.s-1). Nineteen patients among the four groups (21%) were found to have abnormal/probably abnormal swallowing. Swallowing speed was significantly slower in patients who perceived a swallowing problem or who had abnormal symptoms or signs compared with those who did not, providing further evidence for the validity of a timed test of swallowing capacity. The study also provides evidence of a significant incidence of disordered swallowing in outpatients who may not have complained spontaneously but who have diagnoses potentially relevant to swallowing.

Adult↗
PubMed1989

Timing of videofluoroscopic, manometric events, and bolus transit during the oral and pharyngeal phases of swallowing.

The aims of this study were to evaluate and quantify the timing of events associated with the oral and pharyngeal phases of liquid swallows. For this purpose, we recorded 0-20 ml barium swallows in three groups of volunteers using videoradiographic, electromyographic, and manometric methods. The study findings indicated that a leading complex of tongue tip and tongue base movement as well as onset of superior hyoid movement and mylohyoid myoelectric activity occurred in a tight temporal relationship at the inception of swallowing. Two distinct general types of normal swallows were observed. The common "incisor-type" swallow began with the bolus positioned on the tongue with the tongue tip pressed against the upper incisors and maxillary alveolar ridge. At the onset of the "dipper-type" swallow the bolus was located beneath the anterior tongue and the tongue tip scooped the bolus to a supralingual location. Beginning with tongue-tip peristaltic movement at the upper incisors, the two swallow types were identical. Swallow events that occurred after lingual peristaltic movement at the maxillary incisors showed a volume-dependent forward migration in time that led to earlier movement of the hyoid and larynx as well as earlier opening of the upper esophageal sphincter in order to receive the large boluses that arrived sooner in the pharynx during the swallow sequence than did smaller boluses. The study findings indicated that timing of swallow events should be considered in reference to both swallow type and bolus volume. The findings also indicated an important distinction between peristaltic transit and bolus clearance.

Adolescent↗
PubMed2003

Morphologic parameters of normal swallowing events using single-shot fast spin echo dynamic MRI.

This study was designed to determine visible and measurable morphological parameters in normal swallowing using dynamic MRI with single-shot fast spin echo (SSFSE), as a preliminary study in view of noninvasive MRI swallowing evaluation in patients with dysphagia. Seven healthy volunteers aged 24-40 underwent dynamic MRI with SSFSE, with a 1.5-T unit, using a head and neck antenna. Patients repeated dry swallow, water swallow, marshmallow swallow, cake swallow, and cookie chewing for a total of five series, with 15 acquisitions per series at a rate of 700 ms per acquisition. A checklist of swallowing events and anatomic landmarks was used to determine which anatomic landmarks are always visible, which phases or swallowing movements are always visible, and which landmarks can be used to measure oral and pharyngeal motion in swallowing. The oral preparatory, oral, and oropharyngeal phases of deglutition were visible in all cases. No aspiration, reflux, or abnormal residue was observed. Spatial resolution allowed for anatomical measurements of laryngeal elevation, oropharyngeal diameter, and tongue base and velum displacement in all cases. SSFSE dynamic MRI is pertinent for evaluation of the anatomical and physiological characteristics of swallow. The temporal parameters, however, cannot be studied using this technique. Motion artifacts preclude its use in the study of mastication. It remains complementary to videofluoroscopy and other techniques in swallow evaluation.

Adult↗
PubMed2004

Modulation of voluntary swallowing by visual inputs in humans.

The purpose of this study was to test the hypothesis that a stimulus which strengthens a central input to a swallowing-related cortical area, given before voluntary swallowing, could facilitate subsequent swallowing movements. The subjects consisted of seven healthy volunteers. We used visual images to strengthen central input. The subjects voluntarily performed either dry swallowing or water swallowing after presentation of the visual images. Under the water-swallowing condition, the latency was significantly shorter and the maximum amplitude of the suprahyoid electromyographic (EMG) activity was significantly smaller in subjects who received drink-related visual input. However, there were no similar differences under the dry-swallowing condition. In addition, there were no significant differences in the mean EMG amplitude or the duration of EMG activity between subjects who did and did not receive drink-related visual input under either swallowing condition. We concluded that drink-related visual inputs prior to voluntary swallowing facilitate the initiation of swallowing and enhance swallowing-related muscle activity in the presence of peripheral inputs.

Adult↗
PubMed2004

Movement-related cortical potentials associated with saliva and water bolus swallowing.

The purpose of this study was to document the movement-related cortical potentials associated with saliva and water bolus swallowing in seven right-handed healthy humans. As the subjects performed a saliva or water bolus swallowing task, electroencephalograms with electrodes at C3, Cz, and C4 and an electromyogram of the mylohyoid muscle complex were recorded. The early slope, referred to as the Bereitschafts potential, before saliva swallowing was significantly steeper than that before water bolus swallowing. Positive potential amplitude during water bolus swallowing was significantly larger than that during saliva swallowing. Negative slope and motor potential were not clearly present during performance of either swallowing task. Those findings imply that the features of movement-related cortical potential associated with pharyngeal swallowing are different from those associated with limb movement, and that both the cortical process associated with sensory information of pharyngeal swallowing and the cortical preparatory process of pharyngeal swallowing depend on the type of swallowing task.

Adult↗
PubMed1994

Effect of aging, position, and temperature on the threshold volume triggering pharyngeal swallows.

BACKGROUND/AIMS: Swallows triggered by direct stimulation of pharyngeal structures may help to prevent aspiration by emptying the pharynx. The aims of this study were to compare the biomechanical events of the pharyngeal and primary swallow, determine the threshold volume of liquid required to trigger the pharyngeal swallows, and determine the effect of aging, position, and temperature on this threshold volume. METHODS: Concurrent manometry, video fluoroscopy, and video endoscopy were used to study young and elderly healthy volunteers. RESULTS: During pharyngeal swallows, in contrast to primary swallows, the free portion of the tongue did not make contact with the hard palate. In addition, pharyngeal swallows did not result in oral bolus clearance. All other biomechanical events, including deglutitive glottal function, were similar in both types of swallows. The threshold volume for pharyngeal swallows in young volunteers was significantly smaller than in the elderly (P < 0.01). Temperature and position did not have significant effects on threshold volume. CONCLUSIONS: Swallowing is readily induced by water stimulation of the pharynx. Pharyngeal swallows do not induce lingual peristalsis or clearance of oral content. The threshold volume of the pharyngeal swallow is significantly higher in the elderly than in the young, but it is not affected by body position or bolus temperature.

Adult↗
PubMed2000

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 alpha-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.

Deglutition↗
PubMed2002

Comparison of SLN-evoked swallows during rest and chewing in the freely behaving rabbit.

Interactions between the swallowing central neural pathway and the chewing central neural pathway were examined in freely behaving, unanesthetized rabbits. Pharyngeal swallows were elicited by electrical stimulation of the superior laryngeal nerve (SLN) and defined by thyrohyoid muscle (TH) activity in the electromyogram (EMG). Recordings were obtained from rabbits at rest and during chewing. The number of swallows elicited by the SLN stimulation was significantly increased (P<0.001) during quiet oral function (at rest) and during chewing. The increased number of swallows from each baseline was similar, signifying that the effect of the SLN stimulation was similar in generating swallowing in both groups. The swallows induced with SLN stimulation were very similar to natural swallows as defined by the temporal pattern of the EMG duration and the timing of EMG activities. Our results suggest that: (1). the peripheral inputs to the swallowing pathway may rarely be modulated by the chewing pathway in the generation of swallows; (2). the swallowing pathway and the chewing pathway may interact at the level of the rhythm generators; (3). each animal has its own threshold for eliciting pharyngeal swallowing, and the threshold may be independent of the number of chews.

Animals↗
PubMed2003

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.

Animals↗
PubMed2003

Neurophysiology of swallowing.

UNLABELLED: Swallowing is a complex motor event that is difficult to investigate in man by neurophysiological experiments. For this reason, the characteristics of the brain stem pathways have been studied in experimental animals. However, the sequential and orderly activation of the swallowing muscles with the monitoring of the laryngeal excursion can be recorded during deglutition. Although influenced by the sensory and cortical inputs, the sequential muscle activation does not alter from the perioral muscles caudally to the cricopharyngeal sphincter muscle. This is one evidence for the existence of the central pattern generator for human swallowing. The brain stem swallowing network includes the nucleus tractus solitarius and nucleus ambiguus with the reticular formation linking synaptically to cranial motoneuron pools bilaterally. Under normal function, the brain stem swallowing network receives descending inputs from the cerebral cortex. The cortex may trigger deglutition and modulate the brain stem sequential activity. The voluntarily initiated pharyngeal swallow involves several cortical and subcortical pathways. The interactions of regions above the brain stem and the brain stem swallowing network is, at present, not fully understood, particularly in humans. Functional neuroimaging methods were recently introduced into the human swallowing research. It has been shown that volitional swallowing is represented in the multiple cortical regions bilaterally but asymmetrically. Cortical organisation of swallowing can be continuously changed by the continual modulatory ascending sensory input with descending motor output. SIGNIFICANCE: Dysphagia is a severe symptom complex that can be life threatening in a considerable number of patients. Three-fourths of oropharyngeal dysphagia is caused by neurological diseases. Thus, the responsibility of the clinical neurologist and neurophysiologist in the care for the dysphagic patients is twofold. First, we should be more acquainted with the physiology of swallowing and its disorders, in order to care for the dysphagic patients successfully. Second, we need to evaluate the dysphagic problems objectively using practical electromyography methods for the patients' management. Cortical and subcortical functional imaging studies are also important to accumulate more data in order to get more information and in turn to develop new and effective treatment strategies for dysphagic patients.

Brain↗
PubMed2001

Psychometrics of a Chinese translation of the swallowing questionnaire.

AIMS OF THE STUDY: The purpose of this study was to determine the psychometric properties of a Chinese version of a swallowing questionnaire. BACKGROUND/RATIONALE: Impaired swallowing may lead to serious complications if health care professionals do not accurately assess the problem and promptly intervene. The recognition of symptoms indicative of a swallowing problem is essential for nurses. The swallowing questionnaire could provide nurses with a valid instrument to assess patients' impaired swallowing. DESIGNS/METHODS: Phase I consisted of experts doing the initial translation into Chinese and back-translations of the questionnaire. Five experts then determined content validity of the Chinese version, and 35 bilingual subjects determined equivalence of the Chinese translation and English version. Phase II determined concurrent validity and internal consistency using 113 screened medical patients as subjects. Phase III used 105 screened long-term care subjects to determine construct validity. RESULTS/FINDINGS: In Phase I, rating on the appropriateness of items on the Chinese version yielding a content validity index of 0.988. The coefficient of equivalence between the Chinese and English versions of the instrument was 0.81, while per cent agreement for all items on the two versions ranged from 0.80--1.00. Phase II established internal consistency with a K-R20 of 0.74, and concurrent validity yielded a correlation between the swallowing questionnaire and the neurological swallowing exam of 0.675 (P < 0.01). Phase III determined construct validity with significant positive correlations found between the swallowing questionnaire and stroke history and masticatory ability. Significant negative correlations were found between swallowing and cognitive status, functional status and albumin. CONCLUSIONS: Although useful as a tool for nursing assessment and intervention, further work on the swallowing questionnaire such as conducting video fluoroscopy and a swallowing speed test, are recommended to further validate its accuracy.

Activities of Daily Living↗
PubMed2003

Effect of successive swallows on oesophageal motility of normal volunteers, patients with Chagas' disease and patients with idiopathic achalasia.

Most frequently, ten swallows of a 5-mL bolus of water are performed during oesophageal manometry. Our hypothesis is that five swallows may produce the same results. We studied the oesophageal contraction parameters of 40 volunteers, 75 patients with Chagas' disease and 14 patients with idiopathic achalasia. Motility was recorded at 5, 10 and 15 cm above the lower oesophageal sphincter. The subjects performed ten swallows of a 5-mL bolus of water alternated with ten dry swallows with an interval of at least 30 s. We measured the amplitude, duration, peristaltic velocity, number of failed and number of simultaneous contractions of the initial five and final five dry and wet swallows. The comparison of dry and wet swallows showed the differences already known. The comparison of the parameters of the initial five swallows with those of the final five swallows showed no differences. Thus, when the initial five or the final five swallows were considered, there was no change in the conclusions reached by the comparison of patients and volunteers and of dry and wet swallows. We conclude that five swallows may be sufficient for the manometric examination of oesophageal parameters in Chagas' disease and idiopathic achalasia.

Adult↗
PubMed2003

Modulation of human swallowing behaviour by thermal and chemical stimulation in health and after brain injury.

Few data support thermal or chemical stimulation as therapy for neurogenic dysphagia. Our aims were to explore the behavioural effects of thermal (cold) and chemical (citrus) modalities on water swallowing in health (n = 65, mean age 45 years, 44 females) and acute stroke (n = 22, mean age 67 years, eight females). Multiple randomized timed 50-mL swallowing tests were performed for each of four water conditions: (a) room temperature (RT), (b) cold (CD), (c) citrus (CT) and (d) combined cold and citrus (CD + CT). The inter-swallow interval (ISI), swallowing volume velocity (speed), and volume per swallow (capacity) were measured. In health, compared to RT, only CD + CT slowed the speed (12.3 +/- 0.5 vs 10.3 +/- 0.5 mL s(-1), P < 0.03) and decreased the capacity (16.4 +/- 0.9 vs 14.6 +/- 0.7 mL per swallow, P < 0.02) of swallowing. ISI was unaffected, except by CD + CT in healthy young subjects (<60 years) where it was reduced (1.44 +/- 0.02 vs 1.30 +/- 0.02 s, P < 0.02). Despite smaller volumes ingested by stroke patients, CD + CT, compared to RT, again slowed both the speed (3.8 +/- 0.4 vs 4.5 +/- 0.5 mL s(-1), P < 0.03) and capacity (7.6 +/- 0.7 vs 8.5 +/- 0.7 mL per swallow, P < 0.03) of swallowing but had no effect on ISI. We conclude that combined thermal and chemical modification of water consistently alters swallowing behaviour in health and after cerebral injury. These findings have relevance in the management of neurogenic swallowing problems.

Adult↗
PubMed2001

Comparison of effortful and noneffortful swallows in healthy middle-aged and older adults.

OBJECTIVE: To assess the effects of effortful swallowing, a common compensatory strategy for dysphagia, on the bolus and swallowing mechanism of middle-aged and older men and women. DESIGN: Case-controlled design in which subjects completed both the intervention technique and the control behavior. SETTING: A university hospital. PARTICIPANTS: Sixty-four healthy men and women between 45 and 93 years of age from the community. INTERVENTIONS: Participants swallowed 3-mL thin liquid boluses both normally and using the effortful swallow strategy. MAIN OUTCOMES MEASURES: The biomechanics and bolus flow patterns of swallows were analyzed from videofluoroscopic and simultaneous oral pressure data. RESULTS: Subjects at all ages generated significantly increased oral pressures at each sensor location using the effortful swallow (p = .0001), with the pressure increase greater for the middle-aged subjects compared with older subjects. Several durational measures were significantly longer with the effortful swallow including: hyoid maximum anterior excursion (p < .04), laryngeal vestibule closure (p < .0001), and duration of the upper esophageal sphincter opening (p =.0001). The hyoid bone moved further in the superior direction with the effortful swallow (p = .002). There was a trend of decreased oral residue with the effortful swallow (p = .06). CONCLUSION: Biomechanical and bolus flow aspects of swallowing changed when healthy individuals performed effortful swallows with 3-mL boluses.

Age Factors↗
PubMed2000

Age effects on the temporal evolution of isometric and swallowing pressure.

BACKGROUND: The tongue plays a key role in bolus propulsion through the oropharyngeal chamber. In this study, possible age effects on the magnitude and timing of lingual pressure generation were analyzed. METHODS: Oral pressure was measured during isometric and swallowing tasks for 10 elderly (mean age = 81 years) and 10 young (mean age = 51 years) subjects. Three trials each of the isometric task and swallows of three different boluses (3 ml semisolid, 3 ml liquid, and 10 ml liquid) were performed by each subject. The timing and magnitude of isometric and swallowing pressure generation along with the pattern of the swallowing pressure waveform were analyzed. RESULTS: Whereas maximum lingual isometric pressures decreased with age (p < .001). no significant age difference was found for swallowing pressure. Time taken to reach peak pressure also was reduced with age in both the isometric task and swallows of liquid boluses (p < .05), while no significant age effect was found for semisolid swallows. Finally, only elderly subjects showed a pattern of liquid swallowing pressure generation in which multiple lingual gestures were required to reach peak pressure (termed "pressure building"), a pattern demonstrated by both young and elderly groups for semisolids. CONCLUSIONS: Decreased lingual strength with age combined with unchanging swallowing pressure leads to a decreased "pressure reserve," perhaps leaving older individuals more at risk for dysphagia resulting from insults directly or indirectly to the swallowing system. Additionally, swallowing is generally "slowed" with age, apparently due to both central and peripheral factors, and this change may have an impact on bolus flow outcomes.

Aged↗
PubMed2002

Swallowing and speech dysfunction in patients undergoing anterior cervical discectomy and fusion: a prospective, objective preoperative and postoperative assessment.

Swallowing difficulties and dysphonia may occur in patients undergoing anterior cervical discectomy and fusion. The etiology and incidence of these abnormalities, however, are not well defined. In view of this, we performed a prospective, objective analysis of swallowing function and vocal cord approximation in patients undergoing anterior cervical discectomy and fusion. Twenty-three consecutive patients (22 male and one female, mean age 59 years) undergoing anterior cervical discectomy and fusion had standardized modified barium swallow study and videolaryngoendoscopy performed preoperatively and again at 1 week and 1 month postoperatively. Eleven patients (48%) had radiographic evidence of preoperative swallowing abnormalities. The majority of these patients had myelopathic rather than radicular findings (p = 0.03). None, however, had symptoms of swallowing dysfunction. Among these patients, one had worse function postoperatively, three had improvement, and function remained unchanged in seven. The preoperative swallowing assessment was normal in 12 patients (52%). Postoperative radiographic swallowing abnormalities were demonstrated in eight of these patients (67%). Preoperative vocal cord movement was normal in all patients. Postoperatively, vocal cord paresis was detected in two patients. The paresis was transient in one and permanent in the other. Age, previous medical history, operation duration, and spinal level decompressed were not significantly associated with the incidence of swallowing dysfunction. There was, however, a tendency for patients undergoing multilevel surgery to demonstrate an increased incidence of swallowing abnormalities on postoperative radiographic studies. In addition, soft tissue swelling was more frequent in patients whose swallowing function was worse postoperatively (p = 0.007). Postoperative voice and swallowing dysfunction are common complications of anterior cervical discectomy and fusion, although in the majority of patients these abnormalities are not symptomatic. Patients undergoing multilevel procedures are at an increased risk for these complications, in part because of soft tissue swelling in the neck.

Adult↗
PubMed2002

Swallowing-related activities of respiratory and non-respiratory neurons in the nucleus of solitary tract in the rat.

Swallowing-related activity was examined in respiratory (n = 60) and non-respiratory (n = 82) neurons that were located in and around the nucleus of the solitary tract (NTS) in decerebrated, neuromuscularly blocked and artificially ventilated rats. Neurons that were orthodromically activated by electrical stimulation of the superior laryngeal nerve (SLN) were identified, and fictive swallowing was evoked by SLN stimulation. The pharyngeal phase of swallowing was monitored by hypoglossal nerve activity. Two types of non-respiratory neurons with swallowing-related bursts were identified: 'early' swallowing neurons (n = 24) fired during periods of hypoglossal bursts, and 'late' swallowing neurons (n = 8) fired after the end of hypoglossal bursts. The remaining non-respiratory neurons were either suppressed (n = 21) or showed no change in activity (n = 29) during swallowing. On the other hand, respiratory neurons with SLN inputs included 56 inspiratory and four expiratory neurons. Inspiratory neurons were classified into two major types: a group of neurons discharged simultaneously with hypoglossal bursts (type 1 neurons, n = 19), while others were silent during bursts but were active during inter-hypoglossal bursts when swallowing was provoked repetitively (type 2 neurons, n = 34). Three of the expiratory neurons fired during hypoglossal bursts. Many of the swallowing-related non-respiratory neurons and the majority of the inspiratory neurons received presumed monosynaptic inputs from the SLN. Details of the distribution and firing patterns of these NTS neurons, which have been revealed for the first time in a fictive swallowing preparation in the rat, suggest their participation in the initiation, pattern formation and mutual inhibition between swallowing and respiration.

Animals↗