Structural analysis of muscles elevating the hyolaryngeal complex

Presentation of oropharyngeal dysphagia and rehabilitative intervention following esophagectomy: a systematic review

No study has systematically reviewed the evidence on presentation of oropharyngeal dysphagia and swallowing rehabilitation following esophagectomy. The purposes of this systematic review are to 1) qualitatively synthesize the current findings on oropharyngeal swallowing abnormalities identified by instrumental swallowing evaluations, 2) describe the reported health-related outcomes in relation to swallowing abnormality following esophagectomy, and 3) examine the efficacy of reported rehabilitative interventions for oropharyngeal dysphagia in patients who underwent esophagectomy. Publications were searched using five electronic databases. No language or publication date restrictions were imposed. Two authors performed a blind review for published or unpublished studies that reported swallowing biomechanics and dysphagic symptoms using instrumental evaluation of swallowing, specifically the videofluoroscopic swallowing study and fiberoptic endoscopic evaluation of swallowing, and/or health-related outcomes in relation to swallowing abnormalities, and/or therapeutic interventions for oropharyngeal dysphagia following esophagectomy. Twelve studies out of 2,193 studies including 458 patients met the inclusion criteria. Reported abnormal swallowing biomechanics included vocal fold immobility, delayed onset of swallowing, reduced hyolaryngeal elevation, and reduced opening of the upper esophageal sphincter. Aspiration (0-81%) and pharyngeal residue (22-100%) were prevalent. Those abnormal swallowing biomechanics and swallowing symptoms were commonly reported following both transhiatal and transthoracic esophagectomy. Pneumonia presented in 5-25% of the study patients. One quasi-experimental study examined the effectiveness of swallowing exercises for postoperative oropharyngeal dysphagia; three case series reported a benefit of the chin-tuck maneuver in reducing aspiration and residue. This review revealed distinct swallowing impairments and increased pneumonia risks following esophagectomy. This review also found that evidence on the efficacy of therapeutic interventions was limited. Future studies are warranted to develop effective rehabilitative interventions for postesophagectomy patients with oropharyngeal dysphagia.

Metallic Nanoislands on Graphene for Monitoring Swallowing Activity in Head and Neck Cancer Patients

There is a need to monitor patients with cancer of the head and neck postradiation therapy, as diminished swallowing activity can result in disuse atrophy and fibrosis of the swallowing muscles. This paper describes a flexible strain sensor comprising palladium nanoislands on single-layer graphene. These piezoresistive sensors were tested on 14 disease-free head and neck cancer patients with various levels of swallowing function: from nondysphagic to severely dysphagic. The patch-like devices detected differences in (1) the consistencies of food boluses when swallowed and (2) dysphagic and nondysphagic swallows. When surface electromyography (sEMG) is obtained simultaneously with strain data, it is also possible to differentiate swallowing vs nonswallowing events. The plots of resistance vs time are correlated to specific events recorded by video X-ray fluoroscopy. Finally, we developed a machine-learning algorithm to automate the identification of bolus type being swallowed by a healthy subject (86.4%. accuracy). The algorithm was also able to discriminate between swallows of the same bolus from either the healthy subject or a dysphagic patient (94.7% accuracy). Taken together, these results may lead to noninvasive and home-based systems for monitoring of swallowing function and improved quality of life.

Effect of the head extension swallowing exercise on suprahyoid muscle activity in elderly individuals

Aging causes motor function deterioration in the elderly population, which in turn can cause weakness in the muscles associated with swallowing. Swallowing-related problems in elderly individuals can be prevented or their symptoms can be improved with strengthening exercises for the muscles involved in swallowing. The existing strengthening exercises for the suprahyoid muscle have their limitations. Therefore, it is necessary to find another exercise that can be performed by individuals whose personal characteristics make it difficult for them to perform the existing exercises. In this study, we investigated the changes in suprahyoid muscle activation, tongue strength, and thickness of the suprahyoid muscle after 8 weeks of the head extension swallowing exercise (HESE). A total of 23 healthy elderly individuals participated in an 8-week exercise program (20 min/session, 2 times/week for 8 weeks). Suprahyoid muscle activation during effortful swallowing and the effortful-normal ratio were significantly increased at 8 weeks compared to the baseline values (p = 0.002, and 0.033, respectively). Tongue tip pressure, tongue base pressure, normal swallowing pressure, effortful swallowing pressure, and tongue tip endurance were significantly increased at 8 weeks compared with baseline (p = 0.014, 0.004, 0.046, 0.009, and 0.004, respectively). The thickness of the digastric muscle and that of the mylohyoid muscle were significantly increased at 8 weeks compared with baseline (p = 0.000 and 0.004, respectively). This study showed that HESE can be a good option for improving the suprahyoid muscle and tongue strength in the elderly population. Additionally, this exercise does not require any additional equipment and has the advantage of being able to be performed anytime and anywhere. A variety of exercise options tailored according to individual characteristics may be helpful in choosing the most appropriate exercise.

Sonographic assessment of swallowing in irradiated nasopharyngeal carcinoma patients

Objectives/Hypothesis

Ultrasonography is an emerging clinical tool to study the dysfunction of swallowing muscles. This was the first sonographic study to assess the relationship between suprahyoid muscle contraction, hyoid bone displacement, and penetration‐aspiration status (PAS) during swallowing in nasopharyngeal carcinoma (NPC) patients treated with radiotherapy (RT). The study also aimed to establish reliability data for the sonographic technique described.

Study Design

Cross‐sectional study.

Methods

Geniohyoid muscle contraction was quantified using brightness‐mode ultrasonography in this study of 40 post‐RT NPC patients. A series of physiological parameters and PAS were measured using videofluoroscopy.

Results

Intra‐ and inter‐rater agreement values ranged from 0.75 to 0.96 across various sonographic measurements. Percentage increase in the cross‐sectional area of the geniohyoid muscle correlated with anterior (r = 0.42, P < .05) but not superior (r = 0.27, P = .09) hyoid displacement. Anterior hyoid displacement and pharyngeal constriction ratio were significantly associated with PAS score.

Conclusions

Sonographic measurement of suprahyoid muscles provides valuable information on muscle function and is potentially a useful clinical tool in swallowing assessment. Further research is needed to refine the role of this examination in dysphagia.

Level of Evidence

2b. Laryngoscope, 2552–2559, 2018

The pharyngeal contractile integral is a useful indicator of pharyngeal swallowing impairment

BACKGROUND

A limitation to the expanded use of high-resolution pharyngeal manometry (HRPM) in clinical practice is the lack of useful pharyngeal parameters that are easy to interpret, generalizable between patients, and do not require specialized software. In this study, we sought to test the relationship between the pharyngeal contractile integral (PhCI) with videofluoroscopic abnormalities as assessed with the Modified Barium Swallow Impairment Profile^© ™.

METHODS

Adult dysphagic patients were recruited to undergo simultaneous HRPM and videofluoroscopy during a standardized swallowing protocol.

KEY RESULTS

Thirty-six patients were included in the study. The mean PhCI was 247 mm Hg·cm·s (range 2-488 mm Hg·cm·s). The lower pharyngeal total (PT) group (N=20; mean PT=3.9) had a mean PhCI of 299 mm Hg·cm·s, while the higher PT group (N=16; mean PT=12.7) had a mean PhCI score of 188 mm Hg·cm·s (P=.01). There was also a significant negative correlation between normalized PhCI to PT scores (r=-.47; P=.004). Patients with higher PhCIs exhibited less severe penetration-aspiration scores on thin liquids (1.44 vs 3.78; P=.03) and all consistencies combined (1.21 vs 1.99; P=.03).

CONCLUSIONS & INFERENCES

The PhCI is a useful indicator of the presence of pharyngeal swallowing impairment and is technically simple to calculate with currently available software programs. Advancement of software is necessary to refine the clinical value of this parameter. High-resolution pharyngeal manometry has the potential to be a valuable adjunct procedure for the evaluation and treatment of dysphagic individuals.

Expiratory muscle strength training evaluated with simultaneous high-resolution manometry and electromyography

OBJECTIVE

To examine feasibility of a simultaneous high-resolution pharyngeal manometry (HRM) and electromyography (EMG) experimental paradigm to detect swallowing-related patterns of palatal, laryngeal, and pharyngeal muscle activity during expiratory training.

STUDY DESIGN

Technical report.

METHODS

Simultaneous HRM, surface submental, and intramuscular EMG were acquired in two healthy participants during five tasks: 10-cc water swallow, maximum expiratory pressure (MEP) testing, and expiratory muscle strength training (EMST) at three pressure levels (sham, 50%, and 75% MEP).

RESULTS

Experimental conditions were feasible. Velopharyngeal closing pressure, palate EMG activity, and pharyngeal EMG activity increased as expiratory load increased. In contrast, thyroarytenoid EMG activity was low during the expiratory task, consistent with glottic opening during exhalation. Submental EMG patterns were more variable during expiratory tasks. Intraluminal air pressures recorded with HRM were correlated with measured expiratory pressures and target valve-opening pressures of the EMST device.

CONCLUSION

Results suggest that a simultaneous HRM/EMG/EMST paradigm may be used to detect previously unquantified swallowing-related muscle activity during EMST, particularly in the palate and pharynx. Our approach and initial findings will be helpful to guide future hypothesis-driven studies and may enable investigators to evaluate other muscle groups active during these tasks. Defining mechanisms of action is a critical next step toward refining therapeutic algorithms using EMST and other targeted treatments for populations with dysphagia and airway disorders.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:797-804, 2017.

Ultrasonographic Measurement of Thickness of the Thyrohyoid Muscle: A Pilot Study

Objective

To evaluate the normal thickness of the thyrohyoid muscle, which is one of the key muscles related to swallowing, by ultrasonography.

Methods

The thickness of the left and right thyrohyoid muscles was measured in normal male and female adults ranging in age from 20 to 79 years by ultrasonography. The groups were classified according to age as follows: subjects ranging in age from 20 to 39 years were classified into group A, subjects ranging in age from 40 to 59 years were classified into group B, and subjects ranging in age from 60 to 79 years were classified into group C. The measurement level was the line that joins the upper tip of the superior thyroid notch and the oblique line of the thyroid cartilage. Also, a correlation with the thyrohyoid muscle was investigated by collecting information regarding height, weight, body mass index (BMI), age, and gender of subjects in the healthy group.

Results

The number of subjects in each group was as follows: group A (n=82), group B (n=62), and group C (n=60). Also, the thicknesses of the left and right muscles were 2.72±0.65 mm and 2.87±0.76 mm in group A, 2.83±0.61 mm and 2.93±0.67 mm in group B, and 2.59±054 mm and 2.73±0.55 mm in group C, respectively. Thyrohyoid muscle had a correlation with height, weight, and BMI. The thickness of the left and right thyrohyoid muscles was greater in male subjects than in female subjects and the right side muscle was thicker than the left side muscle.

Conclusion

The average thickness of the left and right thyrohyoid muscles was 3.20±0.54 mm in male subjects and 2.34±0.37 mm in female subjects. The thickness of the thyrohyoid muscle was positively correlated with height, weight, and BMI, and the thyrohyoid muscle was thicker in male subjects than in female subjects and the right side muscle was thicker than the left side muscle.

Computational analysis of swallowing mechanics underlying impaired epiglottic inversion

OBJECTIVES/HYPOTHESIS

Determine swallowing mechanics associated with the first and second epiglottic movements, that is, movement to horizontal and full inversion, respectively, to provide a clinical interpretation of impaired epiglottic function.

STUDY DESIGN

Retrospective cohort study.

METHODS

A heterogeneous cohort of patients with swallowing difficulties was identified (n = 92). Two speech-language pathologists reviewed 5-mL thin and 5-mL pudding videofluoroscopic swallow studies per subject, and assigned epiglottic component scores of 0 = complete inversion, 1 = partial inversion, and 2 = no inversion, forming three groups of videos for comparison. Coordinates mapping minimum and maximum excursion of the hyoid, pharynx, larynx, and tongue base during pharyngeal swallowing were recorded using ImageJ software. A canonical variate analysis with post hoc discriminant function analysis of coordinates was performed using MorphoJ software to evaluate mechanical differences between groups. Eigenvectors characterizing swallowing mechanics underlying impaired epiglottic movements were visualized.

RESULTS

Nineteen of 184 video swallows were rejected for poor quality (n = 165). A Goodman-Kruskal index of predictive association showed no correlation between epiglottic component scores and etiologies of dysphagia (λ = .04). A two-way analysis of variance by epiglottic component scores showed no significant interaction effects between sex and age (f = 1.4, P = .25). Discriminant function analysis demonstrated statistically significant mechanical differences between epiglottic component scores: 1 and 2, representing the first epiglottic movement (Mahalanobis distance = 1.13, P = .0007); and 0 and 1, representing the second epiglottic movement (Mahalanobis distance = 0.83, P = .003). Eigenvectors indicate that laryngeal elevation and tongue base retraction underlie both epiglottic movements.

CONCLUSIONS

Results suggest that reduced tongue base retraction and laryngeal elevation underlie impaired first and second epiglottic movements. The styloglossus, hyoglossus, and long pharyngeal muscles are implicated as targets for rehabilitation in dysphagic patients with impaired epiglottic inversion.

LEVEL OF EVIDENCE

2b Laryngoscope, 126:1854-1858, 2016.

A Pilot Study of the Head Extension Swallowing Exercise: New Method for Strengthening Swallowing-Related Muscle Activity

This pilot study examined the effect of a new head extension swallowing exercise (HESE) on submental muscle activity and tongue strength in healthy volunteers. Fifteen young adults (10 females and 5 males) were instructed to extend their head backwards as much as possible, and while watching the ceiling, swallowed their saliva every 10 s for a duration of 20 min. Twenty-four treatments were performed over 8 weeks. The outcome variables evaluated at baseline, 4 and 8 weeks of training, and 12-week follow-up included mean and peak submental muscle activation amplitudes during normal and effortful swallowing measured via surface electromyography, and anterior and posterior isometric tongue pressures were measured with the Iowa Oral Performance Instrument. Results indicated that the muscle activation amplitudes during effortful swallowing increased significantly at 4 and 8 weeks compared to baseline (p < 0.025). However, the increases in amplitudes during normal swallowing were minor (nonsignificant) after 8 weeks compared to baseline. The isometric pressures of the tongue tip and the posterior part of the oral tongue were significantly higher at 8 weeks compared to baseline (p < 0.025). Thus, the 8-week HESE protocol significantly improved suprahyoid muscle activity during effortful swallowing as well as the isometric tongue pressures. The HESE appears effective in exercising and strengthening the suprahyoid muscles and tongue muscles in healthy participants. Although encouraging, these results need to be replicated in clinical trials for testing the therapeutic effects of the HESE in older adults and patients with dysphagia who present with decreased hyolaryngeal elevation.

Impaired swallowing mechanics of post radiation therapy head and neck cancer patients: A retrospective videofluoroscopic study

AIM: To determine swallowing outcomes and hyolaryngeal mechanics associated with post radiation therapy head and neck cancer (rtHNC) patients using videofluoroscopic swallow studies.

METHODS: In this retrospective cohort study, videofluoroscopic images of rtHNC patients (n = 21) were compared with age and gender matched controls (n = 21). Penetration-aspiration of the bolus and bolus residue were measured as swallowing outcome variables. Timing and displacement measurements of the anterior and posterior muscular slings elevating the hyolaryngeal complex were acquired. Coordinate data of anatomical landmarks mapping the action of the anterior muscles (suprahyoid muscles) and posterior muscles (long pharyngeal muscles) were used to calculate the distance measurements, and slice numbers were used to calculate time intervals. Canonical variate analysis with post-hoc discriminant function analysis was performed on coordinate data to determine multivariate mechanics of swallowing associated with treatment. Pharyngeal constriction ratio (PCR) was also measured to determine if weak pharyngeal constriction is associated with post radiation therapy.

RESULTS: The rtHNC group was characterized by poor swallowing outcomes compared to the control group in regards to: Penetration-aspiration scale (P < 0.0001), normalized residue ratio scale (NRRS) for the valleculae (P = 0.002) and NRRS for the piriform sinuses (P = 0.003). Timing and distance measurements of the anterior muscular sling were not significantly different in the two groups, whereas for the PMS time of displacement was abbreviated (P = 0.002) and distance of excursion was reduced (P = 0.02) in the rtHNC group. A canonical variate analysis shows a significant reduction in pharyngeal mechanics in the rtHNC group (P < 0.0001). The PCR was significantly higher in the test group than the control group (P = 0.0001) indicating reduced efficiency in pharyngeal clearance.

CONCLUSION: Using videofluoroscopy, this study shows rtHNC patients have worse swallowing outcomes associated with reduced hyolaryngeal mechanics and pharyngeal constriction compared with controls.

The Effect of Radiation Dose on Swallowing: Evaluation of Aspiration and Kinematics

Radiation oncologists have focused on the pharyngeal constrictors as the primary muscles of concern for dysphagia. However, our prior investigations have demonstrated that radiation dose to the geniohyoid rather than the constrictor muscles was more closely related to penetration aspiration scores (PAS). We examined the relationship between (1) radiation dose and swallowing temporal kinematics, and (2) between PAS and swallowing kinematics in these patients. Videofluoroscopic swallowing studies of 41 patients following radiation therapy for oropharyngeal cancer were analyzed for thin liquid boluses. Timing measures included duration of laryngeal vestibule closure (DLVC), duration to maximum hyoid elevation (DTMHE), duration to cricopharyngeal opening (DTCPO), and pharyngeal transit time (PTT). PAS was extracted for each swallow and considered normal if ≤ 2. As minimum and mean dose to the geniohyoid increased, DTMHE, DTCPO, and PTT increased. Worse PA scores were most strongly correlated with radiation dose received by geniohyoid (r = 0.445, p < 0.0001). Mean DLVC varied according to PAS group (normal PAS mean = 0.67 s, abnormal PAS mean = 0.13 s; p < 0.001). Similarly, DTCPO was significantly different based upon PAS (normal PAS mean = 0.22 s, abnormal PAS mean = 0.37 s, p = 0.016). As PAS increased, DTPCO and PTT increased (r = 0.208, p = 0.04; r = 0.204, p = 0.043). A negative correlation was noted between PAS and DLVC (r = -0.375, p = 0.001). Higher doses of radiation to the geniohyoid muscles are associated with increased severity of dysphagia as measured through both kinematics and PAS. Consideration of dose to the geniohyoid should be considered when planning radiation.

Laryngeal advancement surgery improves swallowing function in a reversible equine dysphagia model

REASONS FOR PERFORMING STUDY

Pharyngeal dysphagia is a debilitating, sometimes fatal condition in horses, with multiple aetiologies. The pathophysiology is complex and not fully understood. Treatment is largely supportive. Laryngeal advancement surgery may diminish symptoms of dysphagia and improve swallowing in affected horses.

OBJECTIVES

1) to induce reversible moderate and marked pharyngeal dysphagia by regional anaesthesia of branches of the glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves; 2) to characterise the dysphagia produced by each model; and 3) to determine whether laryngeal advancement surgery improves swallowing in these models.

STUDY DESIGN

Experimental design using 6 adult horses.

METHODS

Two dysphagia models were produced by blocking IX, the pharyngeal branch of X and XII unilaterally (moderate model) and only the pharyngeal branch of X bilaterally (marked model) within the guttural pouches. Both models were performed on each horse before and after surgery in order to assess the effectiveness of the surgical procedure as a potential treatment for pharyngeal dysphagia. Dysphagia was scored by partly blinded observers on a scale of 0-12 based on observations of eating (nonblinded), endoscopic examinations and fluoroscopic swallowing (blinded), where 0 = normal swallow and 12 = severe dysphagia with tracheal aspiration. Data were analysed by 3-factor ANOVA, with significance taken as P<0.05.

RESULTS

Dysphagia models were reversible, and horses swallowed normally within 3 h of model induction. The marked dysphagia model impaired movement of feed from the base of the tongue to the oesophagus and caused severe airway contamination. The average dysphagia score (mean ± s.d.) for the marked dysphagia model was 10.6 ± 1.1 before surgery and 6.1 ± 4.3 after surgery (P = 0.007). Laryngeal advancement surgery did not significantly improve the dysphagia scores in the moderate model (P = 0.5).

CONCLUSIONS

Laryngeal advancement surgery may improve swallowing and reduce aspiration in horses affected with diseases that cause pharyngeal dysphagia.

Coordinate mapping of hyolaryngeal mechanics in swallowing

Characterizing hyolaryngeal movement is important to dysphagia research. Prior methods require multiple measurements to obtain one kinematic measurement whereas coordinate mapping of hyolaryngeal mechanics using Modified Barium Swallow (MBS) uses one set of coordinates to calculate multiple variables of interest. For demonstration purposes, ten kinematic measurements were generated from one set of coordinates to determine differences in swallowing two different bolus types. Calculations of hyoid excursion against the vertebrae and mandible are correlated to determine the importance of axes of reference. To demonstrate coordinate mapping methodology, 40 MBS studies were randomly selected from a dataset of healthy normal subjects with no known swallowing impairment. A 5 ml thin-liquid bolus and a 5 ml pudding swallows were measured from each subject. Nine coordinates, mapping the cranial base, mandible, vertebrae and elements of the hyolaryngeal complex, were recorded at the frames of minimum and maximum hyolaryngeal excursion. Coordinates were mathematically converted into ten variables of hyolaryngeal mechanics. Inter-rater reliability was evaluated by Intraclass correlation coefficients (ICC). Two-tailed t-tests were used to evaluate differences in kinematics by bolus viscosity. Hyoid excursion measurements against different axes of reference were correlated. Inter-rater reliability among six raters for the 18 coordinates ranged from ICC = 0.90 - 0.97. A slate of ten kinematic measurements was compared by subject between the six raters. One outlier was rejected, and the mean of the remaining reliability scores was ICC = 0.91, 0.84 - 0.96, 95% CI. Two-tailed t-tests with Bonferroni corrections comparing ten kinematic variables (5 ml thin-liquid vs. 5 ml pudding swallows) showed statistically significant differences in hyoid excursion, superior laryngeal movement, and pharyngeal shortening (p < 0.005). Pearson correlations of hyoid excursion measurements from two different axes of reference were: r = 0.62, r2 = 0.38, (thin-liquid); r = 0.52, r2 = 0.27, (pudding). Obtaining landmark coordinates is a reliable method to generate multiple kinematic variables from video fluoroscopic images useful in dysphagia research.

Both head extension and mouth opening impair the ability to swallow in the supine position

Head position and mouth opening in the supine position may impair the ability to swallow. If this does occur, it would lead to retention of intra-oral fluids during dental treatment, which would lead to stimulation of the cough reflex. This study was conducted to investigate how head position and mouth opening affect swallowing ability. The water swallowing test was performed in 13 healthy adult subjects in the supine position. The subjects were asked to swallow 10 mL of water that was injected into the mouth in a single attempt. After swallowing, the residual intra-oral water was suctioned and its volume was measured. An electromyogram (EMG) of the suprahyoid (SH) muscles was also recorded during the test. The duration of SH muscle activity and peak amplitude of SH EMG were examined. The water swallowing test was performed under three head positions (neutral, extended and flexed) and four mouth opening patterns (interincisal distances of 0, 20, 30 and 40 mm). The wider the subject opened the mouth, the more the water remained in the mouth after swallowing. The residual volume of water was more in the extended position compared with that in the neutral and flexed positions. Peak amplitude of SH EMG decreased with mouth opening. Duration of SH muscle activity was longer in the extended position than in the neutral and flexed positions. Head extension and mouth opening can induce difficulty in swallowing in the supine position by extending the duration of SH muscle activity while reducing its intensity.

The Pooling-score (P-score): inter- and intra-rater reliability in endoscopic assessment of the severity of dysphagia

This study evaluated the intra- and inter-rater reliability of the Pooling score (P-score) in clinical endoscopic evaluation of severity of swallowing disorder, considering excess residue in the pharynx and larynx. The score (minimum 4 - maximum 11) is obtained by the sum of the scores given to the site of the bolus, the amount and ability to control residue/bolus pooling, the latter assessed on the basis of cough, raclage, number of dry voluntary or reflex swallowing acts (< 2, 2-5, > 5). Four judges evaluated 30 short films of pharyngeal transit of 10 solid (1/4 of a cracker), 11 creamy (1 tablespoon of jam) and 9 liquid (1 tablespoon of 5 cc of water coloured with methlyene blue, 1 ml in 100 ml) boluses in 23 subjects (10 M/13 F, age from 31 to 76 yrs, mean age 58.56±11.76 years) with different pathologies. The films were randomly distributed on two CDs, which differed in terms of the sequence of the films, and were given to judges (after an explanatory session) at time 0, 24 hours later (time 1) and after 7 days (time 2). The inter- and intra-rater reliability of the P-score was calculated using the intra-class correlation coefficient (ICC; 3,k). The possibility that consistency of boluses could affect the scoring of the films was considered. The ICC for site, amount, management and the P-score total was found to be, respectively, 0.999, 0.997, 1.00 and 0.999. Clinical evaluation of a criterion of severity of a swallowing disorder remains a crucial point in the management of patients with pathologies that predispose to complications. The P-score, derived from static and dynamic parameters, yielded a very high correlation among the scores attributed by the four judges during observations carried out at different times. Bolus consistencies did not affect the outcome of the test: the analysis of variance, performed to verify if the scores attributed by the four judges to the parameters selected, might be influenced by the different consistencies of the boluses, was not significant. These initial data validate the clinical use of the P-score in the management of patients with deglutition disorders by a multidisciplinary team.

Visualizing Hyolaryngeal Mechanics in Swallowing Using Dynamic MRI

INTRODUCTION

Coordinates of anatomical landmarks are captured using dynamic MRI to explore whether a proposed two-sling mechanism underlies hyolaryngeal elevation in pharyngeal swallowing. A principal components analysis (PCA) is applied to coordinates to determine the covariant function of the proposed mechanism.

METHODS

Dynamic MRI (dMRI) data were acquired from eleven healthy subjects during a repeated swallows task. Coordinates mapping the proposed mechanism are collected from each dynamic (frame) of a dynamic MRI swallowing series of a randomly selected subject in order to demonstrate shape changes in a single subject. Coordinates representing minimum and maximum hyolaryngeal elevation of all 11 subjects were also mapped to demonstrate shape changes of the system among all subjects. MophoJ software was used to perform PCA and determine vectors of shape change (eigenvectors) for elements of the two-sling mechanism of hyolaryngeal elevation.

RESULTS

For both single subject and group PCAs, hyolaryngeal elevation accounted for the first principal component of variation. For the single subject PCA, the first principal component accounted for 81.5% of the variance. For the between subjects PCA, the first principal component accounted for 58.5% of the variance. Eigenvectors and shape changes associated with this first principal component are reported.

DISCUSSION

Eigenvectors indicate that two-muscle slings and associated skeletal elements function as components of a covariant mechanism to elevate the hyolaryngeal complex. Morphological analysis is useful to model shape changes in the two-sling mechanism of hyolaryngeal elevation.

The normal swallow: muscular and neurophysiological control

Swallowing is a complex physiologic function that involves precisely coordinated movements within the oral cavity, pharynx, larynx, and esophagus. This article reviews the anatomy, muscular control, and neurophysiological control of normal, healthy swallowing.

Dynamic change in hyoid muscle length associated with trajectory of hyoid bone during swallowing: analysis using 320-row area detector computed tomography

Research on muscle activation patterns during swallowing has been limited. Newly developed 320-row area detector computed tomography (320-ADCT) has excellent spatial and temporal resolution, which facilitates identification of laryngopharyngeal structures and quantitative kinematic analysis of pharyngeal swallowing. We investigated muscle activity patterns by observing the changes in length of hyoid muscles. 320-ADCT was performed in 26 healthy males while swallowing. The following parameters were analyzed three-dimensionally: 1) origins and insertions of the stylohyoid, anterior and posterior digastric, mylohyoid, geniohyoid, and thyrohyoid muscles; and 2) movement of the hyoid bone. The stylohyoid, posterior digastric, and mylohyoid muscles began to shorten simultaneously during the initial stage of swallowing. The shortening of these muscles occurred during the upward movement of the hyoid bone. Subsequently, the geniohyoid, thyrohyoid, and anterior digastric muscles began to shorten, synchronizing with the forward movement of the hyoid bone. A significant correlation was observed between the shortened muscle lengths of the stylohyoid, posterior digastric, and mylohyoid muscles and the upward movement of the hyoid bone ( r = 0.45–0.65). A correlation was also observed between the shortened muscle length of the geniohyoid muscle and the forward movement of the hyoid bone ( r = 0.61). In this study, the sequence of muscle activity during pharyngeal swallowing remained constant. Serial shortening of the hyoid muscles influenced the trajectory of the hyoid bone. The stylohyoid, posterior digastric, and mylohyoid muscles initiated the swallowing reflex and contributed to upward movement of the hyoid bone. The geniohyoid is a key muscle in the forward movement of the hyoid bone.

Activation of upper airway muscles during breathing and swallowing

The upper airway is a complex muscular tube that is used by the respiratory and digestive systems. The upper airway is invested with several small and anatomically peculiar muscles. The muscle fiber orientations and their nervous innervation are both extremely complex, and how the activity of the muscles is initiated and adjusted during complex behaviors is poorly understood. The bulk of the evidence suggests that the entire assembly of tongue and laryngeal muscles operate together but differently during breathing and swallowing, like a ballet rather than a solo performance. Here we review the functional anatomy of the tongue and laryngeal muscles, and their neural innervation. We also consider how muscular activity is altered as respiratory drive changes, and briefly address upper airway muscle control during swallowing.

Evaluating swallowing muscles essential for hyolaryngeal elevation by using muscle functional magnetic resonance imaging

PURPOSE

Reduced hyolaryngeal elevation, a critical event in swallowing, is associated with radiation therapy. Two muscle groups that suspend the hyoid, larynx, and pharynx have been proposed to elevate the hyolaryngeal complex: the suprahyoid and longitudinal pharyngeal muscles. Thought to assist both groups is the thyrohyoid, a muscle intrinsic to the hyolaryngeal complex. Intensity modulated radiation therapy guidelines designed to preserve structures important to swallowing currently exclude the suprahyoid and thyrohyoid muscles. This study used muscle functional magnetic resonance imaging (mfMRI) in normal healthy adults to determine whether both muscle groups are active in swallowing and to test therapeutic exercises thought to be specific to hyolaryngeal elevation.

METHODS AND MATERIALS

mfMRI data were acquired from 11 healthy subjects before and after normal swallowing and after swallowing exercise regimens (the Mendelsohn maneuver and effortful pitch glide). Whole-muscle transverse relaxation time (T2 signal, measured in milliseconds) profiles of 7 test muscles were used to evaluate the physiologic response of each muscle to each condition. Changes in effect size (using the Cohen d measure) of whole-muscle T2 profiles were used to determine which muscles underlie swallowing and swallowing exercises.

RESULTS

Post-swallowing effect size changes (where a d value of >0.20 indicates significant activity during swallowing) for the T2 signal profile of the thyrohyoid was a d value of 0.09; a d value of 0.40 for the mylohyoid, 0.80 for the geniohyoid, 0.04 for the anterior digastric, and 0.25 for the posterior digastric-stylohyoid in the suprahyoid muscle group; and d values of 0.47 for the palatopharyngeus and 0.28 for the stylopharyngeus muscles in the longitudinal pharyngeal muscle group. The Mendelsohn maneuver and effortful pitch glide swallowing exercises showed significant effect size changes for all muscles tested, except for the thyrohyoid.

CONCLUSIONS

Muscles of both the suprahyoid and the longitudinal pharyngeal muscle groups are active in swallowing, and both swallowing exercises effectively target muscles elevating the hyolaryngeal complex. mfMRI is useful in testing swallowing muscle function.