Cadaveric Study and Micro-Computed Tomography of the Anatomy of Palatine Aponeurosis and its Link to the Soft Palate Muscles and Pharyngeal Muscles.

OBJECTIVE: There have been few studies on the anatomy of palatine aponeurosis (PA). Herein, we elucidated the relationship between the PA and soft palate muscles and pharyngeal muscles. DESIGN: Two cadaveric specimens were dissected to observe the gross anatomy of the PA. Six cadaveric specimens were processed and scanned by micro-computed tomography to determine the elaborate anatomy. Images were exported to Mimics software to reconstruct a three-dimensional model. RESULTS: The PA covered the anterior (32.1%-38.8%) of the soft palate, extending from the tensor veli palatini (TVP) and connecting to 3 muscles: palatopharyngeus (PP), uvula muscle, and superior pharyngeal constrictor (SC). The SC and PP are attached to the PA on the medial side of the pterygoid hamulus. SC muscle fibers were attached to the hamulus, forming a distinct gap between the hamulus. Some muscle fibers of the PP and uvula originated from the PA. The PA extended from the TVP to the midline and the posterior edge of the hard palate. The PA was not uniformly distributed, which was complementary to the attached muscles in thickness. CONCLUSIONS: PA, as a flexible fibrous membrane, maintains the shape of the soft palate. It extends from the TVP and covers anteriorly about one-third of the soft palate. The PA provides a platform for the soft palate muscles and pharyngeal muscles, connecting to the PP, uvula muscle, and SC. These muscles are important for palatopharyngeal closure and middle-ear function. It is necessary to minimize the damage to the PA during surgical interventions.

Vascular anatomy of the velopharyngeal muscles and its clinical implications: A fresh cadaveric study based on micro-computed tomography.

Poor speech improvement after levator veli palatini (LVP) reconstruction may be related to intraoperative vascular injury. We aimed to examine the vascular anatomy of the velopharyngeal muscles to provide a guide for arterial protection in cleft palate repair. Fresh adult cadaveric heads were injected with gelatin/lead oxide. The velopharyngeal specimens were stained with iodine and scanned using micro-computed tomography. Three-dimensional reconstruction models were obtained using a computer-aided design software. The ascending palatine artery (APaA), especially the posterior branch, is the main artery supplying the velopharyngeal muscles. The posterior branch of the APaA reaches the dorsal part of the musculus uvulae in the posterior one third of the soft palate (SP) and lies 1.75 mm (standard deviation, 0.06) under the nasal mucosa; the anterior branch penetrates the anterolateral side of the LVP to reach the anterior one third of the SP and lies 7.09 mm (0.03) under the oral mucosa. The posterior APaA, anterior ApaA, and ApaA trunk had mean diameters of 0.41 mm (0.04), 0.46 mm (0.06), and 0.65 mm (0.04) at 0.5, 1, and 1.5 cm distance from the palatal midline, respectively. To minimize vascular injury, mobilization of muscles during intravelar veloplasty should be performed within a distance of 1 cm from the palatal midline, and dissection of the oral submucosa should be reduced in the anterior one third of the SP, while wide dissection of the nasal submucosal should be avoided in the posterior one third of the SP.

Contracted Extravelar Segments of the Levator Veli Palatini Muscle: A Magnetic Resonance Imaging Morphometric Study.

OBJECTIVES: To provide detailed descriptions of contraction-induced morphometric changes in the extravelar segments of the levator veli palatini (LVP) muscle using 3-dimensional (3-D) magnetic resonance imaging (MRI). DESIGN: Three-dimensional MRI data were acquired at rest and during "silent /i/" from 4 singers. During silent /i/, participants voluntarily sustained velar elevation while breathing orally for the entire scan time. Focusing on the extravelar segments, LVP length, angle of the muscle origin, and cross-sectional area (CSA), measurements were obtained and compared between tasks. RESULTS: Three of the 4 participants exhibited the expected patterns of change following concentric contraction of the LVP muscle. Consistent changes from the resting to the contracted state included reductions in LVP length by 13.5% and angle of the muscle origin by 9.8%, as well as increases in CSAs by 22.1%, on average. CONCLUSIONS: This study presented high-resolution data of the LVP muscle behavior with the first in vivo 3-D measurements of the contracted LVP muscle, which can be useful for the validation of computational models that aim at describing biomechanical properties of the LVP muscle in future research. The active behavior of the extravelar LVP muscle also provides some insight on optimal LVP muscle geometry to consider during cleft palate repair.

Velopharyngeal Muscle Morphology in Children With Unrepaired Submucous Cleft Palate: An Imaging Study.

OBJECTIVE: To identify quantitative and qualitative differences in the velopharyngeal musculature and surrounding structures between children with submucous cleft palate (SMCP) and velopharyngeal insufficiency (VPI) and noncleft controls with normal anatomy and normal speech. METHODS: Magnetic resonance imaging was used to evaluate the velopharyngeal mechanism in 20 children between 4 and 9 years of age; 5 with unrepaired SMCP and VPI. Quantitative and qualitative measures of the velum and levator veli palatini in participants with symptomatic SMCP were compared to noncleft controls with normal velopharyngeal anatomy and normal speech. RESULTS: Analysis of covariance revealed that children with symptomatic SMCP demonstrated increased velar genu angle (15.6°, P = .004), decreased α angle (13.2°, P = .37), and longer (5.1 mm, P = .32) and thinner (4 mm, P = .005) levator veli palatini muscles compared to noncleft controls. Qualitative comparisons revealed discontinuity of the levator muscle through the velar midline and absence of a musculus uvulae in children with symptomatic SMCP compared to noncleft controls. CONCLUSIONS: The levator veli palatini muscle is longer, thinner, and discontinuous through the velar midline, and the musculus uvulae is absent in children with SMCP and VPI compared to noncleft controls. The overall velar configuration in children with SMCP and VPI is disadvantageous for achieving adequate velopharyngeal closure necessary for nonnasal speech compared to noncleft controls. These findings add to the body of literature documenting levator muscle, musculus uvulae, and velar and craniometric parameters in children with SMCP.

Evaluation of the Symmetry of the Levator Veli Palatini Muscle and Velopharyngeal Closure Among a Noncleft Adult Population.

PURPOSE: The goal of this study is to determine the typical range of asymmetry between the length and thickness of the levator veli palatini muscle and to explore the impact of the observed asymmetry on velopharyngeal closure. A second objective is to report normative length and thickness of the levator veli palatini muscle among adults with typical velopharyngeal anatomy. METHOD: Magnetic resonance imaging (MRI) data and Amira 5.5 Visualization software were used to evaluate the levator veli palatini muscle among 89 participants with typical velopharyngeal anatomy. Flexible nasopharyngoscopy was used to determine the function of velopharyngeal closure among 39 of the 89 participants with typical velopharyngeal anatomy to examine the functional impact of observed asymmetry. RESULTS: Matched paired t tests demonstrated a nonsignificant difference between the length and thickness of the right and left levator muscle. The mean difference between the right and left length of the levator muscle was 2.28 mm but ranged from 0.09 mm to 10.37 mm. In all cases where individuals displayed asymmetry in the levator muscle through MRI, there was no observed impact on the symmetry of velopharyngeal closure. DISCUSSION: This study suggest that differences in the right and left levator veli palatini muscle are not significant among individuals without cleft palate. However, among individual cases where asymmetry was sizeable, there was no direct impact on the closure pattern. This may suggest there are multiple factors that contribute to asymmetrical velopharyngeal closure that are beyond the level of the levator veli palatini muscle.

Differences in the Tensor Veli Palatini Between Adults With and Without Cleft Palate Using High-Resolution 3-Dimensional Magnetic Resonance Imaging.

OBJECTIVE: To investigate the dimensions of the tensor veli palatini (TVP) muscle in adults with and without cleft palate. DESIGN: Prospective study. PARTICIPANTS: There were a total of 14 adult participants, 8 noncleft and 6 with cleft palate. METHODS: Analysis and comparison of the TVP muscle and surrounding structures was completed using 3D MRI data and Amira 5.5 Visualization Modeling software. TVP muscle volume, hamular process distance, mucosal thickness, TVP muscle length, and TVP muscle diameter were used for comparison between participant groups based upon previous research methods. RESULTS: Mann-Whitney U tests revealed a significantly smaller ( U < .001, P = .002) TVP muscle volume in the cleft palate group (median = 536.22 mm3) compared to individuals in the non-cleft palate group (median = 895.19 mm3). The TVP muscle was also significantly shorter ( U = 1.00, P = .003) in the cleft palate group (median = 18.04 mm) versus the non-cleft palate (median = 21.18 mm). No significant differences were noted for the other measured parameters. CONCLUSION: Significant differences in the TVP muscle volume and length among the noncleft participants found in this study may insights into the reported increased incidence of otitis media with effusion (OME) seen in the cleft population. Results from this study contribute to our understanding of the underlying anatomic differences among individuals with cleft palate.

Clinical Significance of the Levator Veli Palatini Muscle in Velocardiofacial Syndrome Patients: Implications in Velopharyngeal Incompetence and Pharyngeal Flap Surgery.

BACKGROUND: Anatomical variation and deficits of velocardiofacial syndrome patients are related to unsatisfactory treatment results in surgical correction of speech abnormalities. The main purpose of the article is to investigate the clinical significance of thinned levator veli palatini muscle in VCFS patients. METHODS: The authors reviewed medical records of all children with velocardiofacial syndrome who received pharyngeal flap surgery between March 2007 and September 2015. Data including thickness of levator veli palatini in magnetic resonance examination; preoperative velopharyngeal gap size from nasoendoscopy; and preoperative and postoperative speech outcomes were collected. RESULTS: Total of 36 velocardiofacial syndrome patients with preoperative objective data and postoperative speech outcomes were identified. Preoperative velopharyngeal gap showed significant correlation with thickness of levator veli palatini (correlation coefficient: 0.297/0.397, P = .02/.03) and gap size showed correlation with postoperative speech improvement (0.347/0.413, P = .04/.02). However, muscle thickness showed no correlation with speech outcomes (0.046/0.037, P = .77/.86). CONCLUSION: Thinned levator veli palatini muscle in velocardiofacial syndrome patients are related to widened velopharyngeal gap and production of hypernasal speech, and can give negative impact on postoperative surgical outcome of pharyngeal flap surgery.

Morphology of the Levator Veli Palatini Muscle in Adults With Repaired Cleft Palate.

The purpose of this study was to examine differences in levator veli palatini (levator) morphology between adults with repaired cleft palate and adults with noncleft anatomy. Fifteen adult participants (10 with noncleft anatomy, 5 with repaired cleft palate) underwent 3-dimensional (3D) static magnetic resonance imaging (MRI). Image analyses included measures of total muscle volume and the circumference and diameter at 6 points along the length of the muscle. Differences between groups were analyzed using independent sample Mann-Whitney U tests (α < 0.05). Significant differences between groups were noted for measures of muscle volume, circumference at the origin and midline, anterior-posterior diameter at the origin and midline, and superior-inferior diameter at the point of insertion into the velum and midline. Differences in measures at other points along the levator muscle belly were not statistically significant. Limited sample size and gender differences may have impacted statistical findings. Overall, the levator muscle in adults with repaired cleft palate is significantly different than that of adults with noncleft anatomy. This study demonstrates the successful implementation of a method for 3D analysis of velopharyngeal (VP) musculature with potential clinical utility given continued technological advancements in MRI. Continued evaluation of pre- and postsurgical anatomy and short- and long-term outcomes may contribute to a better understanding of the effects of various types of palatoplasties on levator structure, which is important to VP function for speech.

Transillumination of the occult submucous cleft palate.

Occult submucous cleft palate is a congenital deformity characterized by deficient union of the muscles that normally cross the velum and aid in elevation of the soft palate. Despite this insufficient muscle coverage, occult submucous cleft palate by definition lacks clear external anatomic landmarks. This absence of anatomic signs makes diagnosis of occult submucous cleft less obvious, more dependent on ancillary tests, and potentially missed entirely. Current diagnostic methodologies are limited and often are unrevealing in the presurgical patient; however, a missed diagnosis of occult submucous cleft palate can result in velopharyngeal insufficiency and major functional impairment in patients after surgery on the oropharynx. By accurately and easily diagnosing occult submucous cleft palate, it is possible to defer or modify pharyngeal surgical intervention that may further impair velopharyngeal function in susceptible patients. In this report, we introduce transillumination of the soft palate using a transnasal or transoral flexible endoscope as an inexpensive and simple technique for identification of submucous cleft palate. The use of transillumination of an occult submucous cleft palate is illustrated in a patient case and is compared to other current diagnostic methodologies.

Sexual dimorphism of the levator veli palatini muscle: an imaging study.

Objective : Magnetic resonance imaging studies of the levator veli palatini muscle have used small numbers of subjects and have not consistently controlled for sex, race, or age. The purpose of this study was to conduct a structural assessment using a large homogeneous sample to examine the sex differences in the levator muscle morphology. Methods : Thirty white adult subjects (15 men and 15 women) were imaged using a 3 Tesla MRI system. A high-resolution SPACE (sampling perfection with application-optimized contrasts using different flip-angle evolution) sequence was used to acquire images of the velopharyngeal anatomy. Levator muscle measurements were obtained. Results : Men displayed significantly greater levator extravelar segment length (P = .003), levator intravelar segment muscle length (P < .001), greater distance between levator insertion points (P < .001), and greater angles of origin (P = .008) compared with women. There was no statistically significant variation between men and women in the distance between points of origin at the base of the skull. Conclusions : This study provides normative data to improve understanding of levator dysmorphology such as that in cleft palate muscle anatomy. Results of the study demonstrate significant differences between white men and women across several levator muscle measures. Variations in the relative size of the cranium or height of the individual were not proportionate to the variations observed in the levator muscle.

New insights into mechanism of Eustachian tube ventilation based on cine computed tomography images.

There is debate concerning the mechanism of Eustachian tube (ET) ventilation. While a mechanism of complete opening has been advocated previously, sequential contraction of the levator veli palatini and medial pterygoid muscles followed by the tensor veli palatini and lateral pterygoid muscles may produce a transient sequential opening mechanism, allowing an air bolus to traverse the ET. This may explain confusion surrounding sonotubometry reports that not every swallow leads to sound passage in normal subjects. We hypothesize that the ET may not need to open completely when ventilating the middle ear; rather, a discrete air bolus can pass through it. Five normal and five disordered subjects underwent low-radiation dose cine computed tomography (CT) scans of the ET. Sixteen contiguous 2.5 mm slice locations were chosen through a 4 cm area in the nasopharynx that were parallel to and encompassed the entire ET. Twelve images were acquired at each slice over 4.8 s during swallowing and other tasks. Serial images were analyzed. An air bolus was observed passing through the ET in the normal subjects, but not the subject with ET dysfunction. Medial and lateral pterygoid contractions were also observed. A new hypothetical mechanism of transient sequential ET ventilation is presented. This is not a definitive conclusion, as the number of scans taken and maneuvers used was limited. Improved understanding of ET ventilation may facilitate management of middle ear disease as treatment evolves from ventilatory tube placement to ET manipulation.

An Exploratory Investigation of the Palatoglossus Muscle in Children Using Magnetic Resonance Imaging.

PURPOSE: There is currently little evidence reporting the typical morphology of the palatoglossus (PG) muscle. The primary purpose of this exploratory study is to determine whether magnetic resonance imaging (MRI) methods used to quantify the morphology of the levator veli palatini (LVP) muscle can be applied to the PG. The secondary purpose is to provide preliminary data regarding the relationship between the LVP and PG muscles in children. METHOD: Ten children between ages of 4 and 7 years participated in this study. Each participant was scanned using a nonsedated, child-friendly protocol with a T2-weighted, three-dimensional anatomical scan to obtain images of the oropharyngeal anatomy. Custom, oblique-coronal image planes were created to visualize and measure the LVP and PG muscles in their entirety from origin to insertion. Thermo Scientific Amira Software was used to obtain 2D measurements of PG muscle length, width, velar insertion distance, lingual insertion distance, and several angle measurements. RESULTS: The PG ranged from 17.95 to 26.96 mm in length across participants. Velar insertion distance ranged from 17.22 to 30.95 mm. Lingual insertion distance ranged from 26.91 to 36.02 mm. Width ranged from 2.32 to 3.08 mm. The angle formed by the PG and LVP muscle planes ranged from 7.3° to 52.7°. The LVP insertion angle ranged from 42.5° to 75.9°. The PG insertion angle ranged from 16.9° to 52.3°. CONCLUSIONS: MRI was successful in visualizing the PG muscle. The PG was consistent in size and shape within an individual participant but varied across the participant cohort.

Interaction of the craniofacial complex and velopharyngeal musculature on speech resonance in children with 22q11.2 deletion syndrome: An MRI analysis.

There are limited MRI studies of craniofacial and velopharyngeal features in children with 22q11.2 deletion syndrome (22q11.2DS) and to date, none have explored the potential relationship between these features and the speech phenotype. The purpose of this study was to examine the relationship between craniofacial and related velopharyngeal structures in children with 22q11.2DS and to assess their correlation to resonance features using an unsedated MRI protocol. Fifteen children with 22q11.2DS and 15 age- and sex-matched controls with normal velopharyngeal anatomy (ages 4-12 years) successfully completed the study. Analysis of covariance was used to compare differences between the experimental (22q11.2DS) and control (children with normal anatomy) groups. Correlation analyses and regression models were also utilized. The 22q11.2DS group demonstrated significantly shorter nasion-to-sella, sella-to-basion, and basion-to-opisthion distances. The anterior cranial base angle was significantly more obtuse. The levator veli palatini (levator) muscle was significantly thinner and shorter, with an obtuse angle of origin in the 22q11.2DS group. Levator length was significantly correlated with the sella-to-basion measure and hypernasality was correlated with levator origin-to-origin distance. Preliminary results from this study indicate a significant association between hypernasality and levator origin-to-origin distance. Findings from the present study, provide an insight into the pathophysiology of velopharyngeal dysfunction related to this clinically complex population.

Three-Dimensional Anatomy of the Palatopharyngeus and Its Relation to the Levator Veli Palatini Based on Micro-Computed Tomography.

BACKGROUND: Although multiple studies have been reported on the palatopharyngeus and levator veli palatini, their subtle anatomy and functions remain unclear. The authors elucidated the relationship between these muscles and their functional implications based on three-dimensional digital techniques. METHODS: Cadaveric specimens were stained with iodine-potassium iodide and scanned using micro-computed tomography. The muscle fibers were drawn on the exported Imaging and Communications in Medicine images to reconstruct a three-dimensional model and further simplified. RESULTS: In the soft palate, the palatopharyngeus was divided into three bundles. The largest inferior head was found to attach to the palatine aponeurosis, soft palate, and the hard palate on the oral side, which occupied approximately the anterior 28.4 to 36.2 percent of the soft palate in the midline. The superior head was thin and attached to the palatine aponeurosis and the surrounding mucosa on the nasal side. The posterior head was located posterior to the levator veli palatini with fibers attaching to the levator veli palatini and the median portion of the uvula. The levator veli palatini was clasped by the three heads of the palatopharyngeus. The fasciculi of the palatopharyngeus converged into a bundle of muscles at the pharynx and inserted into the lateral and posterior pharyngeal wall. CONCLUSIONS: The palatopharyngeus is the largest muscle that connects the soft palate and pharyngeal wall; it closely coordinates with the levator veli palatini to control levator veli palatini overlifting, narrow the velopharyngeal port with the help of the superior constrictor, and elevate the pharynx. The palatopharyngeus and levator veli palatini help each other in velopharyngeal closure through coordination from other muscles.

Ostmann's Fat Pad-Does it Really Matter?

OBJECTIVE: To compare the size of Ostmann's fat pad (OFP) between healthy ears and ears with chronic otitis media with cholestatoma (COMwC) using magnetic resonance imaging (MRI). METHODS: Twenty-six patients with unilateral COMwC underwent mastoidectomy. Pre-operative MRI records were reviewed retrospectively. The healthy ears served as the control group. OFP is represented by the maximum diameter of the high intensity area medial to the tensor veli palatini muscle (TVP); M1. A reference diameter was defined from the medial border of OFP reaching the medial border of the medial pterygoid muscle; M2. Values of M1, M2 and the ratio of M1:M2 was compared between the healthy and pathological ear in each patient. RESULTS: All 26 patients (16 females,10 males) had unilateral cholestatoma. Mean age was 37.6 years (range 19-83). In the healthy (H) ears group, mean M1H was 2.04 ± 0.53 mm, mean M2H was 9.57 ± 2.57 mm.In the pathological (P) ears group; mean M1P was 2.03 ± 0.55 mm, mean M2P was 9.86 ± 2.37 mm. A comparison of M1 and M2 values between the healthy and pathological ear groups was not statistically significant (P = .853 and P = .509, respectively).Mean M1H:M2H ratio in the healthy ears group was 0.22 ± 0.05, mean M1P:M2P ratio in the pathological ear group was 0.21 ± 0.06. A comparison between these ratios found no significant statistical correlation (P = .607). CONCLUSION: The size of Ostmann's fat pad does not affect the development of chronic otitis media with cholestatoma in adults.

Identifying Predictors of Levator Veli Palatini Muscle Contraction During Speech Using Dynamic Magnetic Resonance Imaging.

Purpose The purpose of this study was to identify predictors of levator veli palatini (LVP) muscle shortening and maximum contraction velocity in adults with normal anatomy. Method Twenty-two Caucasian English-speaking adults with normal speech and resonance were recruited. Participants included 11 men and 11 women (M = 22.8 years, SD = 4.1) with normal anatomy. Static magnetic resonance images were obtained using a three-dimensional static imaging protocol. Midsagittal and oblique coronal planes were established for visualization of the velum and LVP muscle at rest. Dynamic magnetic resonance images were obtained in the oblique coronal plane during production of "ansa." Amira 6.0.1 Visualization and Volume Modeling Software and MATLAB were used to analyze images and calculate LVP shortening and maximum contraction velocity. Results Significant predictors (p < .05) of maximum LVP shortening during velopharyngeal closure included mean extravelar length, LVP origin-to-origin distance, velar thickness, pharyngeal depth, and velopharyngeal ratio. Significant predictors (p < .05) of maximum contraction velocity during velopharyngeal closure included mean extravelar length, intravelar length, LVP origin-to-origin distance, and velar thickness. Conclusions This study identified six velopharyngeal variables that predict LVP muscle function during real-time speech. These predictors should be considered among children and individuals with repaired cleft palate in future studies.

A Dynamic Magnetic Resonance Imaging-Based Method to Examine In Vivo Levator Veli Palatini Muscle Function During Speech.

Purpose The aim of this study was to develop a method able to quantify levator veli palatini (LVP) muscle shortening and contraction velocities using dynamic magnetic resonance imaging (MRI) throughout speech samples and relate these measurements to velopharyngeal portal dimensions. Method Six healthy adults (3 men and 3 women, M = 24.5 years) produced syllables representing 4 different manners of production during real-time dynamic MRI scans. We acquired an oblique-coronal slice of the velopharyngeal mechanism, which captured the length of the LVP, and manually segmented each frame. LVP shortening and muscle velocities were calculated from the acquired images. Results Using our method, we found that subjects demonstrated greater LVP shortening and higher maximum contraction velocities during fricative and plosive syllable production than during nasal or vowel syllable production. LVP shortening and maximum contraction velocity positively correlated with velopharyngeal port depth. Conclusions In vivo LVP function differs between manners of production, as expected, and an individual's velopharyngeal portal dimensions influence LVP function. These measures, contextualized with the force-length and force-velocity muscle relationships, provide new insight into LVP function. Future studies could use this method to investigate LVP function in healthy speakers and individuals with velopharyngeal dysfunction and how function relates to velopharyngeal anatomy.

A novel intraoral injection technique for rat levator veli palatini muscle regeneration.

BACKGROUND: The levator veli palatini (LVP) muscle drives the elevation and retraction of the soft palate to facilitate speech and feeding, but undergoes atrophic changes in patients with cleft palate deformity. This study aimed to establish an effective drug delivery technique for LVP muscle regeneration. METHODS: An intraoral injection technique for rat LVP muscle regeneration was developed based on careful examination of the rat craniofacial anatomy. The accuracy and reliability of this technique were tested by cone-beam computed tomography and nitrocellulose dye labeling. Recombinant human Wnt7a was delivered via this injection technique, and the subsequent responses of the levator veli palatini muscle were analyzed. RESULTS: Both the cone-beam computed tomography orientation of the needle tip and dye labeling suggested repeatable accuracy of the injection technique. Recombinant human Wnt7a delivery via this technique induced regeneration-related changes, including increased expression of centrally nucleated myofibers and Ki67+ve nuclei. CONCLUSION: The intraoral injection technique is safe and efficient. It can be used for accurate drug delivery and to screen regenerative therapeutics for the LVP muscle.

Soft palate muscle activation: a modeling approach for improved understanding of obstructive sleep apnea.

A Hill model-based phenomenological method for muscle activation was used to investigate defectiveness of the palatal muscle tone during sleep for obstructive sleep apnea (OSA) patients. Based on the stretch-stress characteristic of muscle activation when the eccentric contraction is considered, a specifically defined phenomenological strain-energy function was used, as well as the Holzapfel-type strain-energy function for the passive part. A continuum mechanical framework, including the stress tensor and elasticity tensor, was obtained, based on the defined strain-energy function. The model parameters were obtained by fitting the constitutive model to experimental test data. Three-dimensional patient-specific geometry was modeled, accounting for the muscle tissue layer and based on the quantitative histology study of the soft palate. Anatomically representative boundary conditions for the finite element calculation were also considered. Palatal muscle activation level (electromyographic data) versus the negative pressure was defined in the simulations, and the patients' activation level was set to be lower than for the healthy people. The simulation results showed that reduced in activation level for the patients causes a less negative closing pressure, and this makes the soft palate more prone to collapse. In addition, if we account for the passive-active transfer displayed as the muscle contraction corresponding to the neurogenic reflex in the soft palate, the collapse is prevented. This numerical representation of the reduced activation for the OSA patients may provide increased understanding of OSA physiology.