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Tbx1, a DiGeorge syndrome candidate gene, is regulated by sonic hedgehog during pharyngeal arch development.

Appropriate interactions between the epithelium and adjacent neural crest-derived mesenchyme are necessary for normal pharyngeal arch development. Disruption of pharyngeal arch development in humans underlies many of the craniofacial defects observed in the 22q11.2 deletion syndrome (del22q11), but the genes responsible remain unknown. Tbx1 is a T-box transcription factor that lies in the 22q11.2 locus. Tbx1 transcripts were found to be localized to the pharyngeal endoderm and the mesodermal core of the pharyngeal arches, but were not present in the neural crest-derived mesenchyme of the pharyngeal arches. Sonic hedgehog (Shh) is also expressed in the pharyngeal arches and is necessary for normal craniofacial development. We found that Tbx1 expression was dependent upon Shh signaling in mouse embryos, consistent with their overlapping expression in the pharyngeal arches. Furthermore, Shh was sufficient to induce Tbx1 expression when misexpressed in selected regions of chick embryos. These studies reveal a Shh-mediated pathway that regulates Tbx1 during pharyngeal arch development.

Amino Acid Sequence↗

Predictors of outcome following cricopharyngeal disruption for pharyngeal dysphagia.

The indications for, and predictors of outcome following cricopharyngeal disruption in pharyngeal dysphagia are not clearly defined. Our purpose was to examine the symptomatic response to cricopharyngeal disruption, by either myotomy or dilatation, in patients with oral-pharyngeal dysphagia and to determine pre-treatment manometric or radiographic predictors of outcome. Using simultaneous pharyngeal videoradiography and manometry, we studied 20 patients with pharyngeal dysphagia prior to cricopharyngeal dilatation (n = 11) or myotomy (n = 8), and 23 healthy controls. We measured peak pharyngeal pressure, hypopharyngeal intrabolus pressure, upper esophageal sphincter diameter, and coordination. Response rate to sphincter disruption was 65%. The extent of sphincter opening was significantly reduced in patients compared with controls (p = 0.004), but impaired sphincter opening was not a predictor of outcome. Increased hypopharyngeal intrabolus pressures (> 19 mmHg for 10 ml bolus; > 31 mmHg for 20 ml bolus) was a significant predictor of outcome (p = 0.01). Neither peak pharyngeal pressure nor incoordination were predictors of outcome. In pharyngeal dysphagia, hypopharyngeal intrabolus pressure, and not peak pharyngeal pressure, is a predictor of response to cricopharyngeal disruption. The relationship between intrabolus pressure and impaired sphincter opening is an indirect measure of sphincter compliance which helps predict therapeutic response.

Aged↗

Contour tracking using a knowledge-based snake algorithm to construct three-dimensional pharyngeal bolus movement.

Videofluorography (VFG) using a barium-mixed bolus is in wide clinical use for assessing patients with swallowing disorders. VFG is usually done with both lateral (LA) and anterior-posterior (AP) views, most commonly in two separate sittings. A real-time, three-dimensional (3-D) representation of the evolution of a pharyngeal bolus and its volumetric information can potentially help clinicians analyze and visualize the kinematics of swallowing, dysphagia, and compensatory therapeutic strategies. Active contour models, also known as "Snakes," have been used to solve various image analysis and computer vision problems. We applied a Snake algorithm to automate in part the contour tracking and reconstruction of VFG images to visualize and quantitatively analyze the 3-D evolution of a pharyngeal bolus. To improve the accuracy of the Snake search, we provided the additional "knowledge" of the pharyngeal image itself, which served as an extra constraint to push the Snake curve toward the desired contour. VFG of pharyngeal bolus transport in a normal subject was recorded by using barium-mixed boluses (viscosity: 185 centipoise, density: 2.84 g/cc) with volumes of 5, 10, and 20 ml. The resulting LA and AP video images were digitally captured and matched frame by frame. The knowledge-based Snake search algorithm was used to generate Snake points to satisfy both internal (i.e., smoothness) and external (i.e., boundary fitting) constraints. Using these Snake points, we traced the 3-D bolus movement at each time instant, assuming elliptic geometry in the cross-section of the pharyngeal bolus. By concentrating the 3-D images for each time instant, we developed a 3-D movie representing pharyngeal bolus movement. The efficiency, reproducibility, and accuracy of this algorithm in tracing pharyngeal bolus boundaries and estimating front/tail velocities were assessed and found satisfactory. We conclude that 3-D pharyngeal bolus movement can be traced both accurately and efficiently by using a knowledge-based Snake search algorithm.

Algorithms↗

Pharyngeal constriction in elderly dysphagic patients compared with young and elderly nondysphagic controls.

This article reports the results of our study to determine the incidence of abnormalities in timing and extent of pharyngeal constriction in an elderly population with complaints of dysphagia. We performed a retrospective analysis of videofluoroscopic studies, i.e.. dynamic swallow studies, that were performed between 1996 and 1999. Included in the study were patients over 65 years old without an obvious medical or surgical cause for their dysphagia complaints. The timing of maximum pharyngeal constriction was measured relative to the onset of bolus pharyngeal transit, relative to the arrival of the bolus at the upper esophageal sphincter, and relative to the exit of the tail of the bolus from the upper esophageal sphincter. The extent of maximum pharyngeal constriction was measured from a lateral view. Patient data were compared with data gathered from young (18-62 years old) nondysphagic controls and with data gathered from elderly (67-83 years old) nondysphagic controls. We found that 73% of the patient population demonstrated incomplete pharyngeal constriction relative to controls, although the timing of pharyngeal constriction remained coordinated relative to the position of the bolus in the pharynx. Poor pharyngeal constriction, suggestive of pharyngeal weakness, contributed to 75% of the cases of aspiration.

Adult↗

Pharyngeal clearance during swallowing: a combined manometric and videofluoroscopic study.

The deglutitive pharyngeal contraction was analyzed using simultaneous videofluoroscopic and manometric studies of eight volunteers. Anterior, posterior, and longitudinal movements of the pharyngeal surfaces, relative to the cervical vertebrae, were measured during swallows of 5 and 10 mL of liquid barium. Profound pharyngeal shortening during bolus transit through the pharynx eliminated access to the larynx and elevated the upper esophageal sphincter to within 1.5 cm of the retrolingual pharynx. Bolus head movement through the pharynx preceded the propagated pharyngeal contraction and registered manometrically as a slight intrabolus pressure before the major pressure complex. Contraction in the horizontal plane began after bolus head transit and culminated with stripping of the bolus tail through the pharynx. Prolonged upper sphincter opening with the larger-volume swallows resulted from a delayed onset rather than altered propagation of the horizontal pharyngeal contraction. It is concluded that the propagated pharyngeal contraction facilitates pharyngeal clearance but has a minimal role in the process of bolus propulsion during swallowing. The propagated contraction works in concert with profound pharyngeal shortening to minimize hypopharyngeal residue after a swallow.

Adult↗

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↗

An early pharyngeal muscle enhancer from the Caenorhabditis elegans ceh-22 gene is targeted by the Forkhead factor PHA-4.

Caenorhabditis elegans pharyngeal muscle development involves ceh-22, an NK-2 family homeobox gene related to genes controlling heart development in other species. ceh-22 is the earliest known gene expressed in the pharyngeal muscles and is likely regulated directly by factors specifying pharyngeal muscle fate. We have previously implicated the ceh-22 distal enhancer in initiating ceh-22 expression. Here we analyze the distal enhancer using functional and comparative assays. The distal enhancer contains three subelements contributing additively to its activity, and functionally important regulatory sequences are highly conserved in Caenorhabditis briggsae. One subelement, termed DE3, is strongly active in the pharyngeal muscles, and we identified two short oligonucleotides (de199 and de209) contributing to DE3 activity. Multimerized de209 enhances transcription similarly to DE3 specifically in the pharyngeal muscles, suggesting it may be an essential site regulating ceh-22. de209 binds the pan-pharyngeal Forkhead factor PHA-4 in vitro and responds to ectopic pha-4 expression in vivo, suggesting that PHA-4 directly initiates ceh-22 expression through de209. Because de209 enhancer activity is primarily limited to the pharyngeal muscles, we hypothesize that de209 also binds factors functioning with PHA-4 to specifically activate ceh-22 expression in pharyngeal muscle.

Animals↗

Is routine sedation or topical pharyngeal anesthesia beneficial during upper endoscopy?

BACKGROUND: Upper endoscopy is an invasive procedure. However, the benefits of routinely administered sedative medication or topical pharyngeal anesthesic are controversial. The aim of this study was to clarify their effects on patient tolerance and difficulty of upper endoscopy. METHODS: A total of 252 patients scheduled for diagnostic upper endoscopy were randomly assigned to 4 groups: (1) sedation with midazolam and placebo pharyngeal spray (midazolam group), (2) placebo sedation and lidocaine pharyngeal spray (lidocaine group), (3) placebo sedation and placebo pharyngeal spray (placebo group), and (4) no intravenous cannula/pharyngeal spray (control group). The endoscopist and the patient assessed the procedure immediately after the examination. Another questionnaire was sent to the patients 2 weeks later. RESULTS: Patients in the midazolam group rated the examination easier and less uncomfortable compared with those in the other groups. The differences were especially evident in the questionnaires completed 2 weeks after the examination ( p < 0.001). Lidocaine did not significantly improve patient tolerance. However, endoscopists found the procedure easier in patients in the lidocaine group compared with the midazolam ( p < 0.01) and control groups ( p < 0.01) but not the placebo group. CONCLUSIONS: Routine administration of midazolam for sedation increased patient tolerance for upper endoscopy. However, endoscopists found intubation to be more difficult in sedated vs. non-sedated patients. Topical pharyngeal anesthesia did not enhance patient tolerance, but it did make upper endoscopy technically easier compared with endoscopy in patients sedated with midazolam without topical pharyngeal anesthesia, and in patients who had no sedation or pharyngeal anesthesia, but not in patients who received placebo sedation and placebo pharyngeal anesthesia.

Adult↗

Retinoic acid given at late embryonic stage depresses sonic hedgehog and Hoxd-4 expression in the pharyngeal area and induces skeletal malformation in flounder (Paralichthys olivaceus) embryos.

During the development of pharyngeal cartilages, signal molecules, including sonic hedgehog (shh) and various growth factors, as well as Hox genes are expressed in the pharyngeal area. To elucidate whether shh and Hoxd-4 function in pharyngeal cartilage formation in teleost jaw and gill primordia, spatial and temporal patterns of shh expression in flounder (Paralichthys olivaceus) embryonic pharynx were examined. The effects of retinoic acid (RA) on shh and Hoxd-4 expression and the patterning of pharyngeal cartilages were analyzed. At the prim-5 stage, when cartilage precursor cells aggregate in the pharyngeal primordia, pharyngeal endoderm expressed shh in two domains, in portions of the mandibular and hyoid primordia and in the gill primordia. After a further 40 h, shh domains expanded at the posterior edge of the endoderm of each mandibular, hyoid and gill primordium, concurrent with the growth of the primordia. A new shh expression domain appeared at the endodermal border of the mouth. Retinoic acid treatment depressed shh and Hoxd-4 expression, and also reduced the amount of expansion of the shh expression domains. Pharyngeal cartilages that formed in these embryos were malformed; their growth direction was shifted posteriorly and size was reduced. This provides the possibility that shh and Hoxd-4 regulate the growth and direction of pharyngeal cartilage precursor cells and that RA disturbs their expression, causing skeletal malformation.

Amino Acid Sequence↗

[The nasopharynx and pharyngeal tonsil in the history of otology and rhinology. Pictures from the history of otorhinolaryngology, presented by instruments from the collection of the Ingolstadt Medical History Museum].

Anatomy, nomenclature, first clinical observations: In ancient Greece and Rome and in the Middle Ages the posterior opening of the nasal passage was known (Greek "choane" = funnel) as an atomical structure, and it was also known that chronic nasal catarrh is common in children, but it was not realized that this was associated with special pathological alterations. The anatomist H. von Luschka in Tübingen, Germany, was the first to describe the nasopharynx in detail, and he coined the term "pharyngeal tonsil." The otologists of the 19th century like Kramer and Toynbee had placed the Eustachian tube in the center of their investigations and carried out numerous dissections with demonstration of the tubal orifice. They also knew that middle ear infections usually originated in the nasopharynx, but they did not realize that the hypertrophic pharyngeal tonsil was the cause. Posterior rhinoscopy and the diagnosis of the hypertrophy of the pharyngeal tonsil: Czermak in Budapest in 1860 had invented posterior rhinoscopy, and he was the first to diagnose hypertrophic alterations around the tubal orifice and the first to realize that they were the cause of tubal malfunction. Wilhelm Meyer in Kopenhagen in 1868 and 1873-1874 described hypertrophy of the pharyngeal tonsil ("adenoid vegetations") in detail and associated this finding with a syndrome characterized by mouth-breathing, snoring, a typical facial expression, deafness, recurring middle-ear affections, and characteristic alterations of speech. He based his conclusions on 5 years' experience with 175 observations in his office and on examination of 2700 children in Denmark and England. Surgical therapy of adenoid vegetations: Voltolini in Breslau in 1865 had observed a few cases of hypertrophy of the pharyngeal tonsil, and he was the first to treat them by galvanic cauterization. Meyer developed various instruments for reducing the pharyngeal tonsil. They were introduced through the nose while the application of the instrument was assisted digitally via the mouth and pharynx. The operation of the pharyngeal tonsil was adopted very eagerly by a great number of nasal surgeons. Among the numerous special instruments that subsequently were invented the most promising was the ring knife invented by Gottstein in 1886. Anesthesia and positioning: The pioneers of this intervention, Voltolini, Meyer, Semon and others, all operated without any anesthesia, but they usually would need up to 12 sessions (Semon) until the pharyngeal tonsil had been sufficiently reduced. Beckmann in Berlin, who had invented a modification of Gottstein's ring knife, reported in 1897 on more than 5000 cases in which he had removed the adenoids in just one session, in each case without anesthesia. Besides these surgeons, others used cocaine for local anesthesia or chlorethyl or bromethyl for general anesthesia. The German surgeon Edmund Rose (Berlin and Zürich) in 1874 introduced the position with the head suspended for larger interventions like resection ot the maxilla. Rudloff in Wiesbaden, Germany, in 1900 adopted this position for adenoidectomy, but this was generally accepted only after the mouth gags developed by Davis-Boyle and Negus had been introduced. The diagnostic and surgical interventions in the nasopharynx were a powerful link in the process of fusion between otology and rhinolaryngology around the turn of the century. This historical development is described in great detail with many figures and quotations from the literature.

Adenoidectomy↗

A comparison of pharyngeal mucosal pressure and airway sealing pressure with the laryngeal mask airway in anesthetized adult patients.

UNLABELLED: We measured pharyngeal mucosal pressures at six different locations on the laryngeal mask airway (LMA) and tested the hypothesis that the efficacy of the seal is not related to pharyngeal mucosal pressure. Twenty anesthetized, paralyzed adult patients were studied. Microchip sensors were attached to the size 5 LMA at locations corresponding to the lateral and posterior pharynx, the hypopharynx, the pyriform fossa, the base of tongue, and the oropharynx. Mucosal pressures and airway sealing pressures were recorded during inflation of the cuff from 0 to 40 mL in 10-mL increments. The highest mean mucosal pressure was in the oropharynx (26 cm H2O), and the lowest was in the posterior pharynx (2 cm H2O). Mucosal pressures increased with increasing intracuff pressure and cuff volume, but the rate of increase varied among locations. Airway sealing pressure increased with increasing intracuff volume from 0 to 10 mL (P < 0.0001) and 10 to 20 mL (P = 0.0001), was unchanged from 20 to 30 mL, and decreased from 30 to 40 mL (P = 0.005). The airway sealing pressure was higher than pharyngeal mucosal pressure until the intracuff volume was > or =30 mL. There was no correlation between mucosal pressures and airway sealing pressure at any location. We conclude that the efficacy of the seal is not related to pharyngeal mucosal pressure. Pharyngeal mucosal pressures are generally lower than those considered safe for the tracheal mucosa during prolonged intubation. IMPLICATIONS: We measured pharyngeal mucosal pressures at six different locations on the laryngeal mask airway and showed that the efficacy of the seal is not related to pharyngeal mucosal pressure. Pharyngeal mucosal pressures are generally lower than those considered safe for the tracheal mucosa during prolonged intubation.

Adult↗

Symptoms, laryngeal findings, and 24-hour pH monitoring in patients with suspected gastroesophago-pharyngeal reflux.

OBJECTIVES: To investigate the laryngeal signs and symptoms associated with gastroesophago-pharyngeal reflux (GEPR). STUDY DESIGN: A prospective controlled study. METHODS: Nineteen healthy control subjects and 43 patients, 26 with posterior laryngitis (PL) and 17 with a normal larynx and suspected GEPR, were examined using videolaryngoscopy and 24-hour ambulatory dual-probe pH monitoring. RESULTS: Pharyngeal acid reflux occurred in 18 (69%) patients with PL, in 9 (53%) patients with a normal larynx, and in 5 (26%) healthy control subjects. Multiple-comparison procedure showed that pharyngeal reflux was significantly more prevalent in patients with PL than in the healthy control subjects (P < .05). The laryngoscopic findings in patients with pharyngeal reflux varied from normal mucosa to thickening or edema of the posterior wall of the glottis, which was the most frequent finding in the PL group. Erythema was uncommon; it was found only in patients with verified pharyngeal reflux. There was no difference in symptom profile between the patients with PL and patients with a normal larynx or patients with or without pharyngeal reflux. CONCLUSIONS: Pharyngeal reflux is significantly more prevalent in patients with posterior laryngitis than in healthy control subjects. Moreover, a certain degree of pharyngeal reflux appears to be a normal phenomenon. The most common laryngeal finding in patients with posterior laryngitis is thickening or edema of the posterior wall of the glottis. GEPR does not yield specific laryngeal symptoms. Thus, it is unreliable to base the reflux diagnosis on symptoms alone.

Adult↗

Laryngeal adductor reflex and pharyngeal squeeze as predictors of laryngeal penetration and aspiration.

OBJECTIVES: The contribution of laryngopharyngeal (LP) sensory deficits to the outcome of swallowing and the relationship between sensory and motor deficits in the laryngopharynx is unclear. The study purpose is to determine if patients with LP sensory and motor deficits are at increased risk for laryngeal penetration and aspiration during swallowing, and to determine the relationship between pharyngeal motor weakness and LP sensory deficits. MATERIALS AND METHODS: Endoscopic evaluation of swallowing with sensory testing was performed on 122 dysphagic patients who were prospectively divided into two groups. The control group was 76 patients with normal sensitivity, determined by an intact laryngeal adductor reflex (LAR) on air pulse stimulation of the mucosa innervated by the superior laryngeal nerve. The study group was 46 patients with severe sensory deficits, determined by an absent LAR. Each group was given puree followed by thin liquid, noting presence or absence of laryngeal penetration and aspiration. Pharyngeal muscle strength was assessed by noting presence or absence of pharyngeal contraction during voluntary adduction of the vocal folds (pharyngeal squeeze). RESULTS: In control subjects, with purees, 6 of 76 (7.90%) penetrated and 3 of 76 (3.94%) aspirated; with thins, 26 of 76 (34.2%) penetrated and 13 of 76 (17.1%) aspirated. In the absent LAR group, with purees, 39 of 46 (84.8%) penetrated and 32 and 46 (69.6%) aspirated; with thins, 46 of 46 (100%) penetrated and 43 of 46 (93.5%) aspirated. For both consistencies, the differences in prevalence of penetration and aspiration between groups was significant (P <.0001, chi2). In control subjects, pharyngeal squeeze was impaired in 17 of 76 (22.4%), with penetration of puree in 6 of 17 (35.3%) and aspiration in 3 of 17 (17.6%). In the absent LAR group, squeeze was impaired in 41 of 46 (89.1%), with penetration of puree in 39 of 41 (95.1%) and aspiration in 32 of 41 (78.0%). The difference in the prevalence of pharyngeal weakness between groups was significant (P <.0001). The difference in the prevalence of penetration and aspiration was higher in the absent LAR/impaired contraction cohort than in the normal sensation/impaired contraction cohort (P <.0001). CONCLUSION: Absence of the LAR and impaired pharyngeal squeeze puts patients with dysphagia at high risk for laryngeal penetration and aspiration compared with patients with an intact LAR and intact pharyngeal squeeze. There is a strong association between motor and sensory deficits in the laryngopharynx.

Adult↗

Pharyngeal carriage of Neisseria meningitidis and anogenital gonorrhea: evidence for their relationship.

The relationship between pharyngeal carriage of Neisseria meningitidis and anogenital infection with Neisseria gonorrhoeae was investigated at two separate clinics for sexually transmitted diseases in New York City. Of the entire study group of 738 patients, 310 (42%) had pharyngeal N. meningitidis. Gonorrhea appeared in 130 (17.9%) of the 738 patients. Of the 130 patients with anogenital gonorrhea, 73 (56.3%) had N. meningitidis-positive pharyngeal cultures. Neisseria meningitidis was found in the pharyngeal cultures of 39% of the gonorrhea-free patients; 23.2% of patients with N. meningitidis-positive pharyngeal cultures had concomitant anogenital gonorrhea. Of the patients free of pharyngeal N. meningitidis, 13.1% had anogenital gonorrhea. In both facilities, the pharyngeal carriers of N. meningitidis had a 1.9 times greater risk of genital gonorrhea as compared with N. meningitidis-negative patients. Patients with anogenital gonorrhea at both study sites were 1.4-1.7 times more likely to be pharyngeal carriers of N. meningitidis as compared with gonorrhea-free patients.

Anal Canal↗

The role of the endoderm in the development and evolution of the pharyngeal arches.

The oro-pharyngeal apparatus has its origin in a series of bulges found on the lateral surface of the embryonic head, the pharyngeal arches. Significantly, the development of these structures is extremely complex, involving interactions between a number of disparate embryonic cell types: ectoderm, endoderm, mesoderm and neural crest, each of which generates particular components of the arches, and whose development must be co-ordinated to generate the functional adult oro-pharyngeal apparatus. In the past most studies have emphasized the role played by the neural crest, which generates the skeletal elements of the arches, in directing pharyngeal arch development. However, it is now apparent that the pharyngeal endoderm plays an important role in directing arch development. Here we discuss the role of the pharyngeal endoderm in organizing the development of the pharyngeal arches, and the mechanisms that act to pattern the endoderm itself and those which direct its morphogenesis. Finally, we discuss the importance of modification to the pharyngeal endoderm during vertebrate evolution. In particular, we focus on the emergence of the parathyroid gland, which we have recently shown to be the result of the internalization of the gills.

Animals↗

Four-bar linkage modelling in teleost pharyngeal jaws: computer simulations of bite kinetics.

The pharyngeal arches of the red drum (Sciaenops ocellatus) possess large toothplates and a complex musculoskeletal design for biting and crushing hard prey. The morphology of the pharyngeal apparatus is described from dissections of six specimens, with a focus on the geometric conformation of contractile and rotational elements. Four major muscles operate the rotational 4th epibranchial (EB4) and 3rd pharyngobranchial (PB3) elements to create pharyngeal bite force, including the levator posterior (LP), levator externus 3/4 (LE), obliquus posterior (OP) and 3rd obliquus dorsalis (OD). A biomechanical model of upper pharyngeal jaw biting is developed using lever mechanics and four-bar linkage theory from mechanical engineering. A pharyngeal four-bar linkage is proposed that involves the posterior skull as the fixed link, the LP muscle as input link, the epibranchial bone as coupler link and the toothed pharyngobranchial as output link. We used a computer model to simulate contraction of the four major muscles, with the LP as the dominant muscle, the length of which determined the position of the linkage. When modelling lever mechanics, we found that the effective mechanical advantages of the pharyngeal elements were low, resulting in little resultant bite force. By contrast, the force advantage of the four-bar linkage was relatively high, transmitting approximately 50% of the total muscle force to the bite between the toothplates. Pharyngeal linkage modelling enables quantitative functional morphometry of a key component of the fish feeding system, and the model is now available for ontogenetic and comparative analyses of fishes with pharyngeal linkage mechanisms.

Animals↗

A simple procedure for measuring pharyngeal sensitivity: a contribution to the diagnosis of sleep apnoea.

BACKGROUND: Patients with severe apnoea may have an impaired pharyngeal dilating reflex related to decreased pharyngeal sensitivity. The accuracy of a simple new procedure to measure pharyngeal sensitivity and to diagnose sleep disordered breathing (SDB) was investigated. METHODS: Pharyngeal disappearance and appearance sensory perception thresholds were measured by delivering different airflow rates on the soft palate using an intraoral device in 17 controls and 50 patients suffering from SDB evaluated by overnight polygraphy. The procedure was performed before (baseline) and after three successive administrations of a topical anaesthetic to sensitise the pharyngeal sensory impairment. Pharyngeal sensitivity was then evaluated according to SDB severity. SDB was classified as mild, moderate or severe according to the relative proportion of obstructive apnoeas-hypopnoeas and the amount of desaturation. RESULTS: Patients had higher baseline disappearance and appearance sensory thresholds than controls (mean (SD) 0.62 (0.44) v 0.26 (0.06) l/min and 0.85 (0.40) v 0.40 (0.19) l/min, p<0.001, respectively). Such differences were enhanced by topical anaesthesia. Impairment of pharyngeal sensitivity and the number of patients with impaired sensitivity increased from the least to the most severe SDB group as indicated by the test sensitivity for a respiratory disturbance index of >20/hour (50%, 73.7% and 88.5% in the mild, moderate, and severely affected groups, respectively). CONCLUSIONS: This simple and safe procedure showed that impairment of pharyngeal sensitivity is correlated with severity of SDB. Using this test in routine clinical practice may simplify the diagnosis of sleep apnoea, particularly for the most severe patients.

Adult↗

Assessment of pharyngeal airway stability in normal and micrognathic infants.

A current hypothesis for obstructive sleep apnea states that 1) negative airway pressure during inspiration can collapse the pharyngeal airway, and 2) neural control of pharyngeal airway-dilating muscles is important in preventing this collapse. To test this hypothesis we performed nasal mask occlusions to increase negative pharyngeal airway pressures during inspiration in eight normal and five micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by-breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. These findings suggest that nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midinspiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. These findings imply a similar pathophysiology for snoring, spontaneous airway obstruction, and obstruction during snoring.

Airway Obstruction↗