Tongue anatomy and physiology, the scientific basis for a novel targeted neurostimulation system designed for the treatment of obstructive sleep apnea

The dynamic shape changes of the tongue base during respiration, chewing and swallowing

This study aimed to analyze dimensional deformations of the tongue base during respiration, chewing, and swallowing. Eight 7-8-month-old Yucatan minipigs were used. Under deep sedation, eight 2mm ultrasonic piezoelectric (SONO) crystals were implanted in the tongue base forming a cubic-shaped configuration, representing right/left dorsal and ventral lengths, anterior/posterior dorsal and ventral widths, and right/left anterior and posterior thicknesses. Next, 8 pairs of electromyographic (EMG) microelectrodes were inserted into the tongue, jaw, hyoid, pharyngeal, and palatal muscles. SONO and EMG signals during respiration were recorded. Then, minipigs were allowed to wake-up for unrestrained feeding. The feeding sessions were recorded with synchronized EMG and videofluoroscopy to confirm the phases of jaw movement in chewing, and swallowing episodes. Amplitudes, durations, and timings for each dimension of the SONO crystal-circumscribed region were measured from the start of the jaw opening. Findings during respiration showed elongated lengths, anterior widths and anterior thickness (p<0.05). For chewing, the width elongated up to 17% while the length and thickness shortened (12-33% and 10-32% respectively, p<0.05). Onsets of deformational changes in length and thickness occurred 10-30% earlier than in width. The cycle duration was 0.55 ± 0.11seconds chewing, and 0.69 ± 0.16seconds swallowing. During swallowing, the dorsal length (5-12%) and posterior width (10-14%) elongated whereas the posterior thickness (9-15%) and ventral length (4-10%) shortened. Explicit 3D-kinematic patterns in relation to specific functions characterize the tongue base deformation. The findings of this analysis will contribute to a better understanding of the oropharyngeal biomechanics upon abnormal conditions.

The Impact of a Tongue Training Device on Tongue Muscle Strength in Patients with Obstructive Sleep Apnea After Modified Uvulopalatopharyngoplasty: A Pilot Study

Background and Objectives: Sufficient evidence supports the Iowa Oral Performance Instrument (IOPI) as a reliable tool for measuring tongue strength and endurance as well as an effective assessment instrument for intervention studies. This study aimed to investigate the impact of a tongue training device, the HEAL, on tongue muscle strength in patients with obstructive sleep apnea (OSA) following modified uvulopalatopharyngoplasty (UPPP), utilizing the IOPI for evaluation. Materials and Methods: We introduced a tongue strengthener, the HEAL, made from medical-grade silicone, designed to improve tongue strength. Each patient was provided with the HEAL and instructed to begin using it one month after undergoing modified UPPP for OSA. The tongue strength of OSA patients was measured using the IOPI both before using the HEAL and approximately 6 weeks later. Results: A total of 66 participants with OSA underwent modified UPPP and were included in the final analysis. The mean age was 39.15 ± 8.84 years, and the mean BMI was 27.41 ± 4.03 kg/m2. The duration between the pre- and post-assessment of tongue strength using the HEAL was 42.95 ± 17.97 days. The mean tongue strength pressure before and after using the HEAL was 32.16 ± 16.00 kilopascals (kPa) and 42.95 ± 17.97 kPa, respectively. Tongue strength increased by an average of approximately 52.8% after using the HEAL for an approximate duration of 6 weeks. Conclusions: In the current study, participants with OSA who had undergone modified UPPP and subsequently used the HEAL demonstrated an average improvement of 10.79 kPa in tongue strength-an increase of over 50%-as measured by the IOPI. The interval between the pre- and post-assessment of tongue strength was approximately six weeks. Further studies are needed to validate these findings.

Developmental deglutition and intrinsic tongue muscle maturation phenotypes in the Ts65Dn mouse model of Down syndrome

Introduction

Down syndrome (DS) is associated with difficulties with feeding during infancy and childhood. Weaning, or transitioning from nursing to independent deglutition, requires developmental progression in tongue function. However, little is known about whether postnatal tongue muscle maturation is impacted in DS. This study tested the hypothesis that the Ts65Dn mouse model of DS has developmental delays in deglutition, comprised of differences in eating and drinking behaviors relative to euploid controls, coinciding with atypical measures of intrinsic tongue muscle microanatomy.

Methods

The Ts65Dn mouse model of DS and euploid controls were evaluated at 7 days of age (p7; nursing), p21 (weaning), and p35 (mature deglutition) (n = 13-18 mice per group). Eating behavior, drinking behavior, and body weight changes were quantified in p21 and p35 mice through the use of automated monitoring over 24 h. Intrinsic tongues of mice at all three ages were sectioned and stained to permit quantification of the sizes of the four major intrinsic tongue muscles. Transverse intrinsic tongue muscles were evaluated for myofiber size (average myofiber cross sectional area (CSA) of all fibers, MyHC2a fibers, MyHC 2b fibers, and minimum Feret fiber diameter), and percentage of MyHC isoforms (%MyHC2a + fibers, and %MyHC 2b + fibers) in anterior, middle, and posterior regions.

Results

Ts65Dn showed significant differences from euploid in deglutition measures. Compared to euploid, Ts65Dn also showed differences in intrinsic tongue muscle microanatomy and biology. Specifically, Ts65Dn intrinsic tongues had smaller transverse muscle myofiber size measures than control in the anterior and middle tongue, but not in the posterior tongue.

Conclusion

Differences in intrinsic tongue muscles coincide with feeding phenotypes in the Ts65Dn mouse model of DS.

The Influence of the Tongue on the Development of Dental Malocclusion

The tongue supports the upper dental arch and encourages healthy dental arch development when it rests against the roof of the mouth. On the other hand, over time, malocclusion can result from incorrect tongue position, such as lying low in the mouth or thrusting forward during swallowing or speaking. As a muscular organ, the tongue applies forces to the jaws and teeth that may help with malocclusion or hinder it from aligning properly. The dentition and jaws grow and align according to the way the tongue, teeth, and surrounding structures interact. The tongue's morphogenetic function includes forming the arches and having an important impact on the maxillary complex's development. The tongue frequently assumes a balancing and compensatory function in subsequent phases, functioning more or less like a natural orthodontic bite. In adults, the tongue is able to compensate for problems like open bites, teeth that are out of alignment, or differences in the occlusal and sagittal planes of the spine. In this context, the tongue's ability to sustain occlusion during malocclusion can be considered a compensatory response. This is comparable to how lingual dysfunction may contribute to malocclusion or act as a potential source of recurring orthodontic instability. In order to diagnose and treat orthodontic issues, dental professionals must know the connection between tongue position and dental malocclusion. Malocclusion can be prevented or minimized with early intervention, such as myofunctional therapy to correct tongue position and habits, improving dental health and well-being overall.

The relationship of tongue fat content and efficacy of uvulopalatopharyngoplasty in Chinese patients with obstructive sleep apnea

BACKGROUND

To investigate the relationship between tongue fat content and severity of obstructive sleep apnea (OSA) and its effects on the efficacy of uvulopalatopharyngoplasty (UPPP) in the Chinese group.

METHOD

Fifty-two participants concluded to this study were diagnosed as OSA by performing polysomnography (PSG) then they were divided into moderate group and severe group according to apnea hypopnea index (AHI). All of them were also collected a series of data including age, BMI, height, weight, neck circumference, abdominal circumference, magnetic resonance imaging (MRI) of upper airway and the score of Epworth Sleepiness Scale (ESS) on the morning after they completed PSG. The relationship between tongue fat content and severity of OSA as well as the association between tongue fat content in pre-operation and surgical efficacy were analyzed.Participants underwent UPPP and followed up at 3rd month after surgery, and they were divided into two groups according to the surgical efficacy.

RESULTS

There were 7 patients in the moderate OSA group and 45 patients in the severe OSA group. The tongue volume was significantly larger in the severe OSA group than that in the moderate OSA group. There was no difference in tongue fat volume and tongue fat rate between the two groups. There was no association among tongue fat content, AHI, obstructive apnea hypopnea index, obstructive apnea index and Epworth sleepiness scale (all P > 0.05), but tongue fat content was related to the lowest oxygen saturation (r=-0.335, P < 0.05). There was no significantly difference in pre-operative tongue fat content in two different surgical efficacy groups.

CONCLUSIONS

This study didn't show an association between tongue fat content and the severity of OSA in the Chinese group, but it suggested a negative correlation between tongue fat content and the lowest oxygen saturation (LSaO2). Tongue fat content didn't influence surgical efficacy of UPPP in Chinese OSA patients.

TRIAL REGISTRATION

This study didn't report on a clinical trial, it was retrospectively registered.

Targeted Hypoglossal Nerve Stimulation for Patients With Obstructive Sleep Apnea: A Randomized Clinical Trial

Importance

Evidence is lacking from randomized clinical trials of hypoglossal nerve stimulation in obstructive sleep apnea (OSA).

Objective

To evaluate the safety and effectiveness of targeted hypoglossal nerve stimulation (THN) of the proximal hypoglossal nerve in patients with OSA.

Design, Setting, and Participants

This randomized clinical trial (THN3) was conducted at 20 centers and included 138 patients with moderate to severe OSA with an apnea-hypopnea index (AHI) of 20 to 65 events per hour and body mass index (calculated as weight in kilograms divided by height in meters squared) of 35 or less. The trial was conducted from May 2015 through June 2018. Data were analyzed from January 2022 through January 2023.

Intervention

Implant with THN system; randomized 2:1 to activation at month 1 (treatment) or month 4 (control). All received 11 months of THN with follow-up at months 12 and 15, respectively.

Main Outcomes and Measures

Primary effectiveness end points comprised AHI and oxygen desaturation index (ODI) responder rates (RRs). Treatment responses at months 4 and 12/15 were defined as a 50% or greater reduction in AHI to 20 or less per hour and an ODI decrease of 25% or greater. Coprimary end points comprised (1) month 4 AHI and ODI RR in the treatment greater than the control group and (2) month 12/15 AHI and ODI RR in the entire cohort exceeding 50%. Secondary end points included sleep apnea severity (AHI and ODI) and patient-reported outcomes (Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale).

Results

Among 138 participants, the mean (SD) age was 56 (9) years, and 19 (13.8%) were women. Month 4 THN RRs were substantially greater in those in the treatment vs control group (AHI, 52.3% vs 19.6%; ODI, 62.5% vs 41.3%, respectively) with treatment-control standardized mean differences of 0.725 (95% CI, 0.360-1.163) and 0.434 (95% CI, 0.070-0.843) for AHI and ODI RRs, respectively. Months 12/15 RRs were 42.5% and 60.4% for AHI and ODI, respectively. Improvements in AHI, ODI, Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale scores were all clinically meaningful (medium to large effect size). Two serious adverse events and 100 nonserious related adverse events were observed from the implant procedure or study protocol.

Conclusions and Relevance

This randomized clinical trial found that THN demonstrated improvements in sleep apnea, sleepiness, and quality of life in patients with OSAs over an extended AHI and body mass index range without prior knowledge of pharyngeal collapse pattern. Clinically meaningful improvements in AHI and patient-reported responses compared favorably with those of distal hypoglossal nerve stimulation trials, although clinically meaningful differences were not definitive for ODI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02263859.

Hypoglossal nerve trunk stimulation: electromyography findings during drug-induced sleep endoscopy: a case report

BACKGROUND

Literature has demonstrated hypoglossal nerve stimulation to be a safe and effective treatment for patients with obstructive sleep apnea nonadherent to positive airway pressure therapy. However, the recommended criteria for patient selection are still unable to identify all the unresponsive patients, highlighting the need for improved understanding about hypoglossal nerve stimulation for obstructive sleep apnea.

CASE PRESENTATION

A 48-year-old Caucasian male patient with obstructive sleep apnea had been successfully treated with electrical stimulation of the hypoglossal nerve trunk, documented by level 1 polysomnography data. However, due to snoring complaints, he underwent postoperation drug-induced sleep endoscopy for evaluation of electrode activation during upper airway collapse, aiming to improve electrostimulation parameters. Concurrent surface electromyography of the suprahyoid muscles and masseter was obtained. Activation of electrodes 2, 3, and 6 promoted upper airway opening most strongly at the velopharynx and tongue base during drug-induced sleep endoscopy. The same channels also significantly increased the electrical activity on suprahyoid muscles bilaterally, but predominantly on the stimulated side (right). The masseters also presented a considerable asymmetry in electrical potential on the right side (> 55%).

CONCLUSION

Beyond the genioglossus muscle, our findings demonstrate recruitment of other muscles during hypoglossal nerve stimulation, which may be attributed to the electrical stimulation of the nerve trunk. This data provides new insights on how stimulation of the hypoglossal nerve trunk may contribute to obstructive sleep apnea treatment.

Changes in tongue morphology predict responses in pharyngeal patency to selective hypoglossal nerve stimulation

STUDY OBJECTIVES

The major goal of the study was to determine whether changes in tongue morphology under selective hypoglossal nerve therapy for obstructive sleep apnea were associated with alterations in airway patency during sleep when specific portions of the hypoglossal nerve were stimulated.

METHODS

This case series was conducted at the Johns Hopkins Sleep Disorders Center at Johns Hopkins Bayview Medical Center. Twelve patients with apnea implanted with a multichannel targeted hypoglossal nerve-stimulating system underwent midsagittal ultrasound tongue imaging during wakefulness. Changes in tongue shape were characterized by measuring the vertical height and polar dimensions between tongue surface and genioglossi origin in the mandible. Changes in patency were characterized by comparing airflow responses between stimulated and adjacent unstimulated breaths during non-rapid eye movement sleep.

RESULTS

Two distinct morphologic responses were observed. Anterior tongue base and hyoid-bone movement (5.4 [0.4] to 4.1 [1.0] cm (median and [interquartile range]) with concomitant increases in tongue height (5.0 [0.9] to 5.6 [0.7] cm) were associated with decreases in airflow during stimulation. In contrast, comparable anterior hyoid movement (tongue protrusion from 5.8 [0.5] to 4.5 [0.9] cm) without significant increases in height (5.2 [1.6] to 4.6 [0.8] cm) were associated with marked increases in airflow during sleep.

CONCLUSIONS

Tongue protrusion with preservation of tongue shape predicted increases in patency, whereas anterior movement with concomitant increases in height were associated with decreased pharyngeal patency. These findings suggest that pharyngeal patency can be best stabilized by stimulating lingual muscles that maintain tongue shape while protruding the tongue, thereby preventing it from prolapsing posteriorly during sleep.

CITATION

Fleury Curado T, Pham L, Otvos T, et al. Changes in tongue morphology predict responses in pharyngeal patency to selective hypoglossal nerve stimulation. J Clin Sleep Med. 2023;19(5):947-955.

Design and rationale for the treating Obstructive Sleep Apnea using Targeted Hypoglossal Nerve Stimulation (OSPREY) trial

Obstructive sleep apnea (OSA) affects nearly 1 billion people worldwide, including approximately 35 million US residents. OSA has detrimental cardiovascular and neurocognitive consequences. Positive airway pressure corrects sleep disordered breathing but is not always tolerated or used sufficiently. Oral appliances and surgery provide alternatives in select populations but are variably effective. Hypoglossal nerve stimulation can effectively treat obstructive sleep apnea. Targeted hypoglossal nerve stimulation (THN) is simpler than incumbent technology with no sensor and an easier, proximal electrode implantation. The third clinical study of THN, THN3, was the first randomized, controlled trial of hypoglossal nerve stimulation to demonstrate significant improvement of sleep disordered breathing in OSA. The present investigation reports the design of a novel trial of targeted stimulation to provide additional Level 1 evidence in moderate to severe obstructive apnea. OSPREY is a randomized, parallel-arm, 13-month trial wherein all subjects are implanted, 2/3 are activated at Month 1 ("Treatment") and 1/3 are activated at Month 7 ("Control"). The primary endpoint is the difference in apnea-hypopnea index response rates between Treatment and Control groups at Month 7. Secondary endpoints include quality of life and oximetry metrics. OSPREY follows an adaptive "Goldilocks" design which optimizes the number of subjects with the need for high-confidence results. A maximum of 150 subjects is allowed, at which study power of >95% is predicted. Interim analyses begin once 50 patients are randomized and recur after each 20 additional randomizations to detect early success or futility. OSPREY is a unique, efficient trial that should provide high-confidence confirmation of the safety and efficacy of targeted hypoglossal nerve stimulation for moderate to severe obstructive sleep apnea.

Effects of Tongue-Strengthening Exercise on Tongue Strength Reserve and Detraining Effects among Healthy Adults: A Randomized Controlled Trial

Introduction: Tongue strength reserve is the difference between the maximum isometric pressure (MIP) and swallowing pressure of the tongue. People with decreased tongue strength reserve may have a higher risk of presbyphagia or dysphagia. Thus, this study explored the effects of tongue strengthening exercise (TSE) on tongue strength reserve and detraining effects in healthy adults. Materials and Methods: In total, 102 healthy volunteers without any reported history of speech or swallowing deficits were recruited and assigned to experimental (n = 50) and control groups (n = 52). Exercises in the experimental group consisted of compressing an air-filled bulb between the tongue and hard palate for 30 min a day, 5 days a week, for 8 weeks. Thereafter, the experimental group underwent a 4-week detraining period. Results: Following the TSE training, posterior tongue strength reserve (F = 4.92, p = 0.029) of the experimental group was significantly higher than that of the control group. No significant detraining effects were observed on the MIP and swallowing pressure from 4 weeks after the completion of TSE training. Conclusions: According to the study results, TSE may be an effective approach for improving swallowing function.

The impact of daytime transoral neuromuscular stimulation on upper airway physiology - A mechanistic clinical investigation

There is a need for alternatives to positive airway pressure for the treatment of obstructive sleep apnea and snoring. Improving upper airway dilator function might alleviate upper airway obstruction. We hypothesized that transoral neuromuscular stimulation would reduce upper airway collapse in concert with improvement in genioglossal muscle function. Subjects with simple snoring and mild OSA (AHI < 15/h on screening) underwent in-laboratory polysomnography with concurrent genioglossal electromyography (EMGgg) before and after 4-6 weeks of twice-daily transoral neuromuscular stimulation. Twenty patients completed the study: Sixteen males, mean ± SD age 40 ± 13 years, and BMI 26.3 ± 3.8 kg/m² . Although there was no change in non-rapid eye movement EMGgg phasic (p = 0.66) or tonic activity (p = 0.83), and no decrease in snoring or flow limitation, treatment was associated with improvements in tongue endurance, sleep quality, and sleep efficiency. In this protocol, transoral neurostimulation did not result in changes in genioglossal activity or upper airway collapse, but other beneficial effects were noted suggesting a need for additional mechanistic investigation.

Electrical Characterization of the Tongue and the Soft Palate Using Lumped-Element Model for Intraoral Neuromodulation

Intraoral functions are results of complex and well-orchestrated sensorimotor loop operations, and therefore vulnerable to small functional or neural defects. To secure the vital intraoral functions, it is important to find a way to favorably intervene the intraoral sensorimotor loop operations. The tongue and the soft palate are heavily associated with intraoral sensorimotor loops, with their dense neural innervations and occupancy of intraoral space. Therefore, electrical stimulation onto the tongue and the soft palate has a great potential to solve the problems in the intraoral functions. However, the electrical interface for both of them have not been characterized yet as a lumped-element model, for designing electrical stimulation and analyzing its effect. In this study, we measured stimulation thresholds to evoke electrotactile feedback and characterized electrical impedance across electrodes using lumped-element models. We found that average perception/discomfort thresholds for the tongue tip, lateral-inferior side of the tongue, and anterolateral side of the soft palate as 0.18/1.31, 0.37/3.99, and 1.19/7.55 mA, respectively. An R-C-R-R-C model represented the electrical interface across the tongue and the soft palate with the highest accuracy. The average component values of the R-C-R-R-C model were found as 2.72kΩ, 45.25nF, 1.27kΩ, 22.09GΩ, and 53.00nF, on average.

A novel intraoral neuromuscular stimulation device for treating sleep-disordered breathing

Purpose

To ascertain the usefulness of a novel intraoral neuromuscular stimulation device in treating patients with primary snoring and mild obstructive sleep apnoea (OSA). This device uses daytime awake neuromuscular electrical stimulation (NMES) as an application to induce toning of the tongue muscles.

Methods

A prospective cohort study of 70 patients with sleep-disordered breathing was conducted. Objective snoring and respiratory parameters were recorded with 2 consecutive night WatchPat sleep studies before and after treatment. The device was used for 20 min once daily for a 6-week period. Secondary outcome measures using visual analogue scale reporting of snoring by patient and Epworth Sleepiness Score (ESS) were recorded. Quality of life parameters were also noted.

Results

Objective reduction of snoring was noted on the sleep studies in 95% of participants, with an average snoring time reduction of 48%. Subjectively, the visual analogue scale reported by partners’ similarly demonstrated reduction in 95% of the patients with an average reduction of 40%. In a subset of 38 patients with mild OSA, AHI reduced from 9.8 to 4.7/h (52% reduction), ODI 7.8 to 4.3/h (45% reduction), and ESS from 9.0 to 5.1. Adverse effects encountered were minimal.

Conclusion

This prospective cohort study demonstrates a notable improvement in both objective and subjective parameters of snoring and mild OSA in both simple snorers and patients with mild OSA. This device offers a safe and novel approach to reduce snoring and mild OSA by utilising intraoral neuromuscular electrical stimulation. This could be a preferred option for patients as it alleviates the need of using an oral device during sleep.

Trial registration

clinicaltrials.gov identifier NCT03829956

The Hypoglossal Nerve Stimulation as a Novel Therapy for Treating Obstructive Sleep Apnea-A Literature Review

Obstructive sleep apnea (OSA) is a common sleep disorder that affects all age groups and is associated with many co-morbid diseases (especially cardiovascular diseases). Continuous positive airway pressure (CPAP) is the gold standard for treating OSA. However, adherence to PAP therapy has been a major challenge with an estimated adherence between 20% and 80%. Mandibular advancement devices (MAD) are a good alternative option if used in the appropriate patient. MAD are most effective in mild and moderate OSA but not severe OSA. Surgical options are invasive, not appropriate for severe OSA, and associated with pain and long healing time. Hypoglossal nerve stimulation (HGNS), or upper airway stimulation (UAS), is a novel therapy in treating moderate and severe degrees of OSA in patients who cannot tolerate CPAP therapy. We reviewed the MEDLINE (PubMed) database. The search process yielded 303 articles; 31 met the inclusion and exclusion criteria and were included. We concluded that hypoglossal nerve stimulation is a very effective and novel alternative therapy for moderate and severe OSA in patients who cannot tolerate CPAP therapy. Adherence to HGNS is superior to CPAP. However, more developments are needed to ensure the highest safety profile.

Designer Receptors Exclusively Activated by Designer Drugs Approach to Treatment of Sleep-disordered Breathing

Rationale: Obstructive sleep apnea is recurrent upper airway obstruction caused by a loss of upper airway muscle tone during sleep. The main goal of our study was to determine if designer receptors exclusively activated by designer drugs (DREADD) could be used to activate the genioglossus muscle as a potential novel treatment strategy for sleep apnea. We have previously shown that the prototypical DREADD ligand clozapine-N-oxide increased pharyngeal diameter in mice expressing DREADD in the hypoglossal nucleus. However, the need for direct brainstem viral injections and clozapine-N-oxide toxicity diminished translational potential of this approach, and breathing during sleep was not examined.Objectives: Here, we took advantage of our model of sleep-disordered breathing in diet-induced obese mice, retrograde properties of the adeno-associated virus serotype 9 (AAV9) viral vector, and the novel DREADD ligand J60.Methods: We administered AAV9-hSyn-hM3(Gq)-mCherry or control AAV9 into the genioglossus muscle of diet-induced obese mice and examined the effect of J60 on genioglossus activity, pharyngeal patency, and breathing during sleep.Measurements and Main Results: Compared with control, J60 increased genioglossus tonic activity by greater than sixfold and tongue uptake of 2-deoxy-2-[¹⁸F]fluoro-d-glucose by 1.5-fold. J60 increased pharyngeal patency and relieved upper airway obstruction during non-REM sleep.Conclusions: We conclude that following intralingual administration of AAV9-DREADD, J60 can activate the genioglossus muscle and improve pharyngeal patency and breathing during sleep.

Ultrasound Localization and Percutaneous Electrical Stimulation of the Hypoglossal Nerve and Ansa Cervicalis

OBJECTIVE

Hypoglossal nerve stimulation for obstructive sleep apnea (OSA) can be effective for appropriately selected patients, but current patient selection criteria are complex and still result in a proportion of nonresponders. Ansa cervicalis stimulation of the infrahyoid cervical strap muscles has recently been proposed as a new form of respiratory neurostimulation (RNS) therapy for OSA treatment. We hypothesized that percutaneous stimulation of both nerves in humans with temporary electrodes would make testing of the physiologic response to different RNS strategies possible.

STUDY DESIGN

Nonrandomized acute physiology study.

SETTING

Tertiary care hospital.

METHODS

Fifteen participants with OSA underwent ultrasonography and placement of percutaneous electrodes proximal to the medial division of the hypoglossal nerve and the branch of the ansa cervicalis innervating the sternothyroid muscle (ACST). Procedural success was documented in each participant, as were any failures or procedural complication.

RESULTS

The hypoglossal nerve was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 13 of 15 (86.7%). The ACST was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 14 of 15 (93.3%). Stimulation failure of the hypoglossal nerve was due to suboptimal electrode placement in 1 participant and electrode displacement in the other 2 cases. No complications occurred.

CONCLUSIONS

The hypoglossal nerve and ACST can be safely stimulated via percutaneous electrode placement. Larger trials of percutaneous stimulation may help to identify responders to different RNS therapies for OSA with temporary or permanent percutaneous electrodes. Techniques for electrode design, nerve localization, and electrode placement are described.

Safety and effectiveness in explantation and re-implantation of hypoglossal nerve stimulation devices

PURPOSE

Since 2001, hypoglossal nerve stimulators have been implanted in patients with obstructive sleep apnea around the world, initially in trial situations but more recently also in regular care settings. Medium term data indicate effectiveness and tolerability of treatment. However, when assessing the safety of the procedure, the safe feasibility of explantation or reimplantation must also be considered.

PATIENTS AND METHODS

Nine patients with an implanted respiratory-driven hypoglossal nerve stimulator. We have evaluated the feasibility and safety of explantation or re-implantation with another stimulation system.

RESULTS

In 2012, nine patients were implanted with a respiratory-driven hypoglossal nerve stimulator as part of the Apnex Medical Pivotal Study. The study was ended in 2013. For a variety of reasons, the system was explanted from all nine patients by the year 2019. Three of these patients were re-implanted with a different system with respiratory sensing during the same session (mean incision to closure time for explantation 88.2 ± 35.01 min., mean incision to closure time for re-implantation 221.75 ± 52.73 min.). Due to extensive scar tissue formation, all procedures were technically challenging. Complication rate was significantly higher when re-implantation was performed or attempted in the same surgical session (0 of 5 patients with explantation versus 3 of 4 patients with attempted re-implantation; p = 0.018). There was no significant difference between the AHI values before and after implantation in patients with re-implantation.

CONCLUSION

Explantation and re-implantation are technically challenging though possible procedures. The single-staged equilateral reimplantation of another hypoglossal nerve stimulation system can, but need not, be successful.

Effects of inhaled fluticasone propionate on extrinsic tongue muscles in rats

Obstructive sleep apnea (OSA) is more common in patients with asthma, and inhaled corticosteroids may contribute to OSA pathogenesis in these patients. This study tested the effects of orally inhaled fluticasone propionate (FP) on extrinsic tongue muscles. Unanesthetized rats were treated with FP or placebo for 28 days. On day 29, tongue retrusive and protrusive functions were tested via hypoglossal nerve stimulation under a state of anesthesia, followed by genioglossus (GG), styloglossus (SG) and hyoglossus (HG) muscle extraction, after euthanasia, for histology [myosin heavy chain (MHC) fibers and laminin content reflecting extracellular matrix (ECM)]. On protrusive testing, FP increased percent maximum tetanic force at 40 Hz (P = 0.03 vs. placebo) and endurance index (P = 0.029 vs. placebo). On retrusive testing, FP increased maximum twitch (P = 0.026 vs. placebo) and tetanic forces (P = 0.02 vs. placebo) with no effect on endurance index. On histology, FP increased GG cross-sectional area of MHC type IIa (P = 0.036 vs. placebo) and tended to increase type IIb (P = 0.057 vs. placebo) fibers and HG MHC IIx fibers (P = 0.065). The FP group had significantly increased laminin-stained areas, of greatest magnitude in the HG muscle. FP affects tongue protrusive and retrusive functions differently, concurrent with a shift in MHC fibers and increased ECM accumulation. These differential alterations may destabilize the tongue's "muscle hydrostat" during sleep and promote collapse.NEW & NOTEWORTHY The effects of inhaled corticosteroid on upper airway may contribute to OSA pathogenesis in asthma. In this study, we tested the effects of orally inhaled fluticasone propionate on tongue protrusive and retrusive functions and on tongue extrinsic muscle fiber composition and molecular properties. We found that fluticasone treatment: 1) increased protrusive endurance and retrusive maximum twitch and tetanic force; and 2) on histology, increased cross-sectional area of myosin heavy chain (MHC) type IIa fibers and tended to increase cross-sectional area of MHC type IIb fibers in the protrusive muscle and of MHC IIx fibers in the retrusors. It also increased laminin-stained areas, across extrinsic tongue muscles, of greatest magnitude in the retrusors; and 3) reduced protein degradation and activated pathways associated with increased protein synthesis in the protrusor. These differential effects on the protrusors and retrusors may destabilize the tongue's "muscle hydrostat" properties during sleep and promote collapse.

Effects of a comprehensive physical therapy on moderate and severe obstructive sleep apnea- a preliminary randomized controlled trial

BACKGROUND

Critically compromised by upper airway anatomical impaired properties, obstructive sleep apnea (OSA) can be categorized into different phenotypic traits, mainly including oropharyngeal muscle dysfunction. The upper airway muscle strength training was targeted on oropharyngeal muscle dysfunction by re-educating the oropharyngeal muscles to maintain the upper airway patency. OSA was characterized with multilevel collapsibility of the upper airway; however, the programs are still inconsistent and the effects are unknown. Therefore, the purpose of this study was to investigate the effects of a comprehensive physical therapy on OSA.

METHODS

Fifteen subjects with newly diagnosed moderate or severe OSA (AHI ≥ 15) were randomized into intervention and control groups. The intervention group underwent a 12-week-intervention of hospital based physical therapy, while the control group was kept on waiting for 12 weeks. Polysomnography (PSG) data, oropharyngeal and respiratory muscle performance were measured before and after intervention.

RESULTS

In intervention group (n = 8), AHI was significantly improved (from 46.96 ± 19.45 to 32.78 ± 10.78 events/h, p = 0.017); in control group (n = 7), AHI was significantly increased (from 35.77 ± 17.49 to 42.96 ± 17.32 events/h, p = 0.043). While the control group remained no change between pre- and post- intervention, the intervention group demonstrated that other PSG outcomes significantly improved, including arousal index (46.04 ± 18.9 versus 32.98 ± 8.35/h), mean SpO₂ (92.88 ± 2.1 versus 94.13 ± 1.46%), and oxygen desaturation index (ODI) (31.13 ± 19.48 versus 20.57 ± 7.83/h).

CONCLUSION

This comprehensive physical therapy can be prescribed for the significant clinical improvement on sleep apnea for the patients with moderate and severe OSA.

Bilateral hypoglossal nerve stimulation for treatment of adult obstructive sleep apnoea

BACKGROUND AND AIM

Hypoglossal nerve stimulation (HNS) decreases obstructive sleep apnoea (OSA) severity via genioglossus muscle activation and decreased upper airway collapsibility. This study assessed the safety and effectiveness at 6 months post-implantation of a novel device delivering bilateral HNS via a small implanted electrode activated by a unit worn externally, to treat OSA: the Genio™ system.

METHODS

This prospective, open-label, non-randomised, single-arm treatment study was conducted at eight centres in three countries (Australia, France and the UK). Primary outcomes were incidence of device-related serious adverse events and change in the apnoea-hypopnoea index (AHI). The secondary outcome was the change in the 4% oxygen desaturation index (ODI). Additional outcomes included measures of sleepiness, quality of life, snoring and device use. This trial was registered with ClinicalTrials.gov, number NCT03048604.

RESULTS

22 out of 27 implanted participants (63% male, aged 55.9±12.0 years, body mass index (BMI) 27.4±3.0 kg·m^-2) completed the protocol. At 6 months BMI was unchanged (p=0.85); AHI decreased from 23.7±12.2 to 12.9±10.1 events·h^-1, a mean change of 10.8 events·h^-1 (p<0.001); and ODI decreased from 19.1±11.2 to 9.8±6.9 events·h^-1, a mean change of 9.3 events·h^-1 (p<0.001). Daytime sleepiness (Epworth Sleepiness Scale; p=0.01) and sleep-related quality of life (Functional Outcomes of Sleep Questionnaire-10; p=0.02) both improved significantly. The number of bed partners reporting loud, very intense snoring, or leaving the bedroom due to participant snoring decreased from 96% to 35%. 91% of participants reported device use >5 days per week, and 77% reported use for >5 h per night. No device-related serious adverse events occurred during the 6-month post-implantation period.

CONCLUSIONS

Bilateral HNS using the Genio™ system reduces OSA severity and improves quality of life without device-related complications. The results are comparable with previously published HNS systems despite minimal implanted components and a simple stimulation algorithm.

Models of anatomically based oropharyngeal rehabilitation with a multilevel approach for patients with obstructive sleep apnea: a meta-synthesis and meta-analysis

OBJECTIVES

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder associated with dysfunction of oropharyngeal muscles to maintain upper airway patency during sleep. Oropharyngeal rehabilitation (OPR) was developed to restore, reconstruct, and reeducate oropharyngeal muscle function, but current protocols and effectiveness of OPR have been inconsistent. The purpose of this study was to review (1) indications of OPR, (2) protocols of OPR, and (3) effectiveness of OPR.

METHODS

We searched MEDLINE, EMBASE, and the Cochrane Library and then conducted both meta-synthesis and meta-analysis according to the statement of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA).

RESULTS

A total of eight studies with 203 patients were included. By means of meta-synthesis, the patients with middle age, BMI < 40 kg/m², mild-to-moderate OSA, and non-severe upper airway anatomical abnormality were found to benefit from OPR. The protocol of OPR was summarized to be an anatomically based, multilevel approach, including the retropalatal, retroglossal, hypopharyngeal, TMJ, and facial levels. By using meta-analysis, overall outcomes were presented as apnea hypopnea index (AHI) with significant improvement from 25.2 ± 7.8/h to 16.1 ± 6.6/h (mean difference [MD] - 9.8 [95% CI - 11.0 to - 8.6], p < 0.0001); the lowest oxygen saturation (LSAT) improved from 80.2 ± 4.7 to 83.8 ± 2.9% (MD 3.0% [95% CI 2.0 to 4.0], p < 0.0001); Epworth sleepiness scale (ESS) improved from 11.8 ± 1.9 to 6.3 ± 1.6 (MD - 5.9 [95% CI - 7.5 to - 4.2], p < 0.001), neck circumference (NC) from 35.2 ± 1.1 to 34.7 ± 0.9 cm (MD - 0.6 [95% CI - 0.9 to - 0.2], p = 0.002), BMI from 24.8 ± 3.7 to 24.8 ± 4.1 kg/m² (MD - 0.0; 95% CI - 0.5 to 0.5, p = 0.95). All outcomes except BMI demonstrated significant improvement from OPR.

CONCLUSIONS

Meta-analysis of previous OPR reports shows an improvement in AHI of 39%, compared with the usual surgical definition of success at 50%. Only mild and moderate cases of OSA were referred for OPR in the prior studies. In order to improve outcomes with OPR, a comprehensive approach to rehabilitation should be emphasized.

The Role of Animal Models in Developing Pharmacotherapy for Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a highly prevalent disease characterized by recurrent closure of the upper airway during sleep. It has a complex pathophysiology involving four main phenotypes. An abnormal upper airway anatomy is the key factor that predisposes to sleep-related collapse of the pharynx, but it may not be sufficient for OSA development. Non-anatomical traits, including (1) a compromised neuromuscular response of the upper airway to obstruction, (2) an unstable respiratory control (high loop gain), and (3) a low arousal threshold, predict the development of OSA in association with anatomical abnormalities. Current therapies for OSA, such as continuous positive airway pressure (CPAP) and oral appliances, have poor adherence or variable efficacy among patients. The search for novel therapeutic approaches for OSA, including pharmacological agents, has been pursued over the past years. New insights into OSA pharmacotherapy have been provided by preclinical studies, which highlight the importance of appropriate use of animal models of OSA, their applicability, and limitations. In the present review, we discuss potential pharmacological targets for OSA discovered using animal models.

[Pathophysiology of obstructive sleep apnea]

The prevalence of obstructive sleep apnea (OSA) is considered to be very high in western industrialized countries. There are conservative and surgical forms of treatment for OSA; however, the pathophysiology is largely unexplained and cannot be explained by anatomical abnormalities alone. In recent years, a number of non-anatomical factors have been found that favor the development of OSA. These include the respiratory excitation threshold (arousals), the respiratory drive (loop gain), as well as the control and function of the muscular upper airway dilators. The understanding of the individual pathophysiological processes may be helpful in the future to develop individual treatment approaches for patients.

The Anatomical Relationships of the Tongue with the Body System

The tongue plays a fundamental role in several body functions such as swallowing, breathing, speaking, and chewing. Its action is not confined to the oral cavity, but it affects lower limb muscle strength and posture. The tongue is an organ that has an autocrine/paracrine mechanism of action to synthesize different substances to interact with the whole body; according to a line of thought, it is also an extension of the enteric system. The aim of this study was to review the functions of the tongue and its anatomical association with the body system. According to the authors' knowledge, this is the first scientific article focusing on the tongue in a systemic context. In a clinical evaluation, connections with the tongue should be considered to optimize the clinical examination of the tongue and therefore enhance rehabilitation programs and therapeutic results.

Silencing of Hypoglossal Motoneurons Leads to Sleep Disordered Breathing in Lean Mice

Obstructive Sleep Apnea (OSA) is a prevalent condition and a major cause of morbidity and mortality in Western Society. The loss of motor input to the tongue and specifically to the genioglossus muscle during sleep is associated with pharyngeal collapsibility and the development of OSA. We applied a novel chemogenetic method to develop a mouse model of sleep disordered breathing Our goal was to reversibly silence neuromotor input to the genioglossal muscle using an adeno-associated viral vector carrying inhibitory designer receptors exclusively activated by designer drugs AAV5-hM4Di-mCherry (DREADD), which was delivered bilaterally to the hypoglossal nucleus in fifteen C57BL/6J mice. In the in vivo experiment, 4 weeks after the viral administration mice were injected with a DREADD ligand clozapine-N-oxide (CNO, i.p., 1mg/kg) or saline followed by a sleep study; a week later treatments were alternated and a second sleep study was performed. Inspiratory flow limitation was recognized by the presence of a plateau in mid-respiratory flow; oxyhemoglobin desaturations were defined as desaturations >4% from baseline. In the in vitro electrophysiology experiment, four males and three females of 5 days of age were used. Sixteen-nineteen days after DREADD injection brain slices of medulla were prepared and individual hypoglossal motoneurons were recorded before and after CNO application. Positive mCherry staining was detected in the hypoglossal nucleus in all mice confirming successful targeting. In sleep studies, CNO markedly increased the frequency of flow limitation n NREM sleep (from 1.9 ± 1.3% after vehicle injection to 14.2 ± 3.4% after CNO, p < 0.05) and REM sleep (from 22.3% ± 4.1% to 30.9 ± 4.6%, respectively, p < 0.05) compared to saline treatment, but there was no significant oxyhemoglobin desaturation or sleep fragmentation. Electrophysiology recording in brain slices showed that CNO inhibited firing frequency of DREADD-containing hypoglossal motoneurons. We conclude that chemogenetic approach allows to silence hypoglossal motoneurons in mice, which leads to sleep disordered breathing manifested by inspiratory flow limitation during NREM and REM sleep without oxyhemoglobin desaturation or sleep fragmentation. Other co-morbid factors, such as compromised upper airway anatomy, may be needed to achieve recurrent pharyngeal obstruction observed in OSA.

A comparative study: tongue muscle performance in weightlifters and runners

Exercise mode (i.e., resistance training, endurance training) is known to yield mode-specific effects on strength and endurance of muscles that are directly targeted during the exercise. Such mode-specific effects can also be observed in indirectly involved (i.e., nontargeted) muscles. Mode-specific muscle performance changes of nontargeted muscles, however, have only been investigated within the skeletal system. Therefore, as a first step, this study aimed to determine if bulbar muscle performance (tongue strength [TS], tongue endurance [TE]) differs between weightlifters and runners and if group differences are tongue region-specific. The Iowa Oral Performance Instrument (IOPI) was used to measure TS and TE of the anterior and posterior tongue regions in 21 weightlifters and 23 runners. In weightlifters anterior TS was significantly greater than posterior TS (P = 0.008), whereas in runners anterior and posterior TS were comparable. Furthermore, weightlifters produced significantly greater anterior TS than runners (P = 0.001). Finally, TE was overall significantly greater in runners than in weightlifters (P = 0.001). Findings suggest that exercise mode may differentially impact performance patterns of nontargeted bulbar muscles. More research is warranted to better understand the mechanisms underlying tongue muscle performance differences between weightlifters and runners.

Neurostimulation Treatment of OSA

Over the past 30 years, hypoglossal nerve stimulation has moved through a development pathway to become a viable treatment modality for patients with OSA. Initial pilot studies in animals and humans laid the conceptual foundation for this approach, leading to the development of fully implantable stimulating systems for therapeutic purposes. These devices were then shown to be both safe and efficacious in feasibility studies. One such closed-loop stimulating device was found to be effective in treating a limited spectrum of apneic patients and is currently approved by the US Food and Drug Administration for this purpose. Another open-loop stimulating system is currently being rigorously tested in a pivotal trial. Collectively, clinical trials of hypoglossal nerve stimulating systems have yielded important insights that can help optimize therapeutic responses to hypoglossal nerve stimulation. These insights include specific patient selection criteria and methods for delivering stimulation to specific portions of the hypoglossal nerve and/or genioglossus muscle. New approaches for activating efferent and afferent motor pathways are currently in early-stage laboratory development and hold some long-term promise as a novel therapy.

Hypoglossal nerve stimulation in a pre-clinical anesthetized rabbit model relevant to OSA

We tested the functional effects of hypoglossal (CNXII) stimulation in the anesthetized rabbit before and after injections of saline into the tongue base to obstruct the airway. Data (n = 6) show little or no effect of CN XII trunk stimulation; however, medial branch stimulation (20-100 Hz; 50-500 μs pulse width, and incremental increases from 10 μA) reduced upper airway resistance. Medial branch stimulation was less effective in reducing resistance than anterior advancement of the hyoid. Endoscopic viewing (n-3) of the retropalate showed this region as the narrowest and dynamically changed by anterior hyoid displacement, with less evident effects than CNXII stimulation. We conclude that under these conditions CNXII medial branch stimulation reduces airway resistance, especially after induced obstruction.

Insights since FDA Approval of Hypoglossal Nerve Stimulation for the Treatment of Obstructive Sleep Apnea

Purpose

The literature on hypoglossal nerve stimulation (HNS) for the treatment of moderate-to-severe obstructive sleep apnea (OSA) was reviewed from 2014, the time of FDA approval for the Inspire Systems device, to 2017 for themes that might be useful conceptually and practically in the consideration of this new non-anatomic surgical therapy.

Recent Findings

there are now further follow-up articles since the 12-month results for Apnea Reduction (STAR) trial of the Inspire device, and post-approval publications which report similar and/0r improved AHI outcomes. Other emerging themes include drug-induced sedation endoscopy (DISE) as a tool in assessment of eligibility and a more detailed understanding of mechanisms for an HNS effects.

Summary

The post-STAR literature provides guidelines for an integrated coordination of medicine and surgery to appropriately screen and manage patients.

Specific branches of hypoglossal nerve to genioglossus muscle as a potential target of selective neurostimulation in obstructive sleep apnea: anatomical and morphometric study

PURPOSE

To determine the ideal implantation site for selective tongue neurostimulation in obstructive sleep apnea, anatomy of the distal branching of the hypoglossal nerve (HGN) was revisited.

METHODS

The HGN distal course and intramuscular distribution to the tongue muscles were studied in 17 embalmed and 5 fresh heads (age 60-98, BMI 20-35). Medial branches supplying selectively the genioglossus (GG) muscle were identified. Then, the distinct bundles entering the oblique (GGo) and horizontal (GGh) parts of the GG were located. Morphometric data were compared to similar measurements made on MRI sections from 12 patients (age 43-71, BMI 18-47).

RESULTS

The key facts relevant to optimize stimulation and electrode design are the following: the mean width of both GG muscles in embalmed and fresh cadavers was 20.7 ± 2.9 and 21.4 ± 5 mm, respectively; it is significantly (p < 0.05) superior to the MRI value of 18.26 ± 2.0 mm. Selective nervous branches for GGh and GGo were located at 52 ± 8% of hyoid bone-mandibular symphysis distance and at 5.8 ± 1.1 mm from the inferior border of the GG muscle. The surface of stimulation is a 4.4 ± 1.1 × 6.9 ± 3.8 mm ellipse.

CONCLUSIONS

According to our observations, the optimal selective or supra-selective stimulation of the tongue protractor muscles can be performed on the lateral surface of the GG at roughly equal distance between the mandibular symphysis and the hyoid bone, at a depth of about 0.6 cm above the GG lower border.

Chemogenetic stimulation of the hypoglossal neurons improves upper airway patency

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep. OSA leads to high cardiovascular morbidity and mortality. The pathogenesis of OSA has been linked to a defect in neuromuscular control of the pharynx. There is no effective pharmacotherapy for OSA. The objective of this study was to determine whether upper airway patency can be improved using chemogenetic approach by deploying designer receptors exclusively activated by designer drug (DREADD) in the hypoglossal motorneurons. DREADD (rAAV5-hSyn-hM3(Gq)-mCherry) and control virus (rAAV5-hSyn-EGFP) were stereotactically administered to the hypoglossal nucleus of C57BL/6J mice. In 6-8 weeks genioglossus EMG and dynamic MRI of the upper airway were performed before and after administration of the DREADD ligand clozapine-N-oxide (CNO) or vehicle (saline). In DREADD-treated mice, CNO activated the genioglossus muscle and markedly dilated the pharynx, whereas saline had no effect. Control virus treated mice showed no effect of CNO. Our results suggest that chemogenetic approach can be considered as a treatment option for OSA and other motorneuron disorders.

Tongue strength and endurance: Comparison in active and non-active young and older adults

PURPOSE

Tongue strength and endurance are important for swallowing and upper airway patency. Physical activity positively affects targeted and non-targeted skeletal muscles; however, little is known about the indirect effect of physical activity on tongue muscles. This study sought to determine if tongue muscle performance differs between highly active and non-active individuals and if such an effect varies with age.

METHOD

Forty-eight healthy adults were divided into two age groups (24 young, 20.96 ± 3.22 years; 24 older, 65 ± 3.72 years) and further divided into highly active and non-active based on The General Practice Physical Activity Questionnaire. Tongue strength (TS) and tongue endurance (TE) were obtained using the Iowa Oral Performance Instrument.

RESULT

A significant main effect of activity level on TS and TE was found. Although the main effect of age on TS and TE and age × activity level interactions were not significant, the effect of activity level on TS and TE was more pronounced in older adults than younger adults.

CONCLUSION

Findings suggest physical activity may affect TS and TE, particularly in older adults. Future research is warranted to understand the underlying mechanisms contributing to these group differences. Clinical implications of these findings are discussed.

Tongue prints: A novel biometric and potential forensic tool

Tongue is a vital internal organ well encased within the oral cavity and protected from the environment. It has unique features which differ from individual to individual and even between identical twins. The color, shape, and surface features are characteristic of every individual, and this serves as a tool for identification. Many modes of biometric systems have come into existence such as fingerprint, iris scan, skin color, signature verification, voice recognition, and face recognition. The search for a new personal identification method secure has led to the use of the lingual impression or the tongue print as a method of biometric authentication. Tongue characteristics exhibit sexual dimorphism thus aiding in the identification of the person. Emerging as a novel biometric tool, tongue prints also hold the promise of a potential forensic tool. This review highlights the uniqueness of tongue prints and its superiority over other biometric identification systems. The various methods of tongue print collection and the classification of tongue features are also elucidated.

Hypoglossal nerve stimulation for obstructive sleep apnea: A review of the literature

Objective

To review the indications and clinical evidence supporting hypoglossal nerve stimulation (HNS) therapy for the treatment of moderate-to-severe obstructive sleep apnea (OSA).

Methods

Peer reviewed literature on hypoglossal nerve stimulation therapy for obstructive sleep apnea from 2001 to 2016.

Results

The only currently FDA-approved HNS device for the treatment of moderate-to-severe OSA is produced by Inspire Medical Systems, which recently published its 36-month outcomes data from its Stimulation Therapy for Apnea Reduction (STAR) trial. HNS therapy is currently indicated for moderate-to-severe OSA patients who are CPAP-intolerant, have a body mass index <32, apnea-hypopnea index <50, and without a concentric pattern of upper airway collapse on sleep endoscopy.

Conclusions

Data from the STAR trial suggests that a subset of OSA patients can achieve a significant therapeutic response from hypoglossal nerve stimulation. However, these results may be limited in their generalizability to the broader OSA population.

[Implantable nerve stimulation for obstructive sleep apnea hypopnea syndrome]

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a common disorder that has been identified as a contributor to cardiovascular disease making it a major public health problem. Continuous positive airway pressure is the standard treatment but compliance is suboptimal. Mandibular advancement devices and surgery have limited indications, inconstant efficiency and potential irreversible side effects. Stimulation of the hypoglossal nerve, that innervates the genioglossus, a protrusor muscle of the tongue, is now a new treatment option for moderate and severe cases of OSAHS. Two types of stimulation are currently available: stimulation synchronous with inspiration and continuous stimulation. The indication of each type of stimulation and long-term effects still need to be assessed but the implantable nerve stimulation is a promising treatment for patients without a therapy solution so far.

Real-time prediction of disordered breathing events in people with obstructive sleep apnea

PURPOSE

Conventional therapies for obstructive sleep apnea (OSA) are effective but suffer from poor patient adherence and may not fully alleviate major OSA-associated cardiovascular risk factors or improve certain aspects of quality of life. Predicting the onset of disordered breathing events in OSA patients may lead to improved strategies for treating OSA and inform our understanding of underlying disease mechanisms. In this work, we describe a deployable system capable of performing real-time predictions of sleep disordered breathing events in patients diagnosed with OSA, providing a novel approach for gaining insight into OSA pathophysiology, discovering population subgroups, and improving therapies.

METHODS

LArge Memory STorage and Retrieval artificial neural networks with 864 different configurations were applied to polysomnogram records from 64 patients. Wavelet transforms, measures of entropy, and other statistics were applied to six physiological signals to provide network inputs. Approximate statistical tests were used to determine the best performing network for each patient. The most important predictors of disordered breathing events in OSA patients were determined by analyzing internal network parameters.

RESULTS

The average optimized individual prediction sensitivity and specificity were 0.81 and 0.77, respectively. Predictions were better than random guessing for all OSA patients. Analysis of internal network parameters revealed a high degree of heterogeneity among disordered breathing event predictors and may reveal patient subgroups.

CONCLUSIONS

We report the first practical system to predict individual disordered breathing events in a heterogeneous group of patients diagnosed with OSA. The pattern of disordered breathing predictors suggests variable underlying pathophysiological mechanisms and highlights the need for an individualized approach to OSA diagnosis, therapy, and management.

Electrical stimulation of the hypoglossal nerve: a potential therapy

Obstructive sleep apnea is characterized by recurrent episodes of pharyngeal collapse, which result from a decrease in pharyngeal dilator muscle tone. The genioglossus is a major pharyngeal dilator that maintains airway patency during sleep. Early studies in animal and humans have demonstrated that electrical stimulation of this muscle reduces pharyngeal collapsibility, increases airflow, and mitigates obstructive sleep apnea. These findings impelled the development of fully implantable hypoglossal nerve stimulating systems (HGNS), for which feasibility trial results are now available. These pilot studies have confirmed that hypoglossal nerve stimulation can prevent pharyngeal collapse without arousing patients from sleep. Potentially, a substantial segment of the patient population with obstructive sleep apnea can be treated with this novel approach. Furthermore, the feasibility trial findings suggest that the therapeutic potential of HGNS can be optimized by selecting patients judiciously, titrating the stimulus intensity optimally, and characterizing the underlying function and anatomy of the pharynx. These strategies are currently being examined in ongoing pivotal trials of HGNS.