Contemporary Sleep Surgery: From Reconstruction To Restoration

Stanley Yung-Chuan Liu, MD, DDS, and Rishi Jay Gupta, DDS, MD, MBA

ABSTRACT

Obstructive sleep apnea (OSA) is a prevalent condition that affects people of all ages. Surgical management has improved with growing understanding of OSA pathophysiology, new methods of airway phenotyping and precision in operative techniques. The classic Stanford phased approach serves as a foundation for the updated algorithm, which places surgery on a continuum with medical and dental care. The last 40 years have seen a burgeoning of effort focused on individual surgical or dental procedural success rates. What lies ahead should be a focus on improving overall treatment success, usually achievable only with multimodal interventions. The goal of treatment success for the OSA patient will foster collaboration across disciplines.

Key words: Snoring, obstructive sleep apnea, maxillomandibular advancement, hypoglossal nerve stimulation, temporomandibular disorders, tonsillectomy, UPPP, DOME

AUTHORS

Stanley Yung-Chuan Liu, MD, DDS, is an assistant professor of otolaryngology and, by courtesy, of plastic and reconstructive surgery at the Stanford University School of Medicine. He is director of the Stanford sleep surgery fellowship and preceptor to the oculoplastic surgery fellowship. Dr. Liu is a Stanford biodesign faculty fellow alumnus, a diplomate of the American Board of Oral and Maxillofacial Surgery, a fellow of the American College of Surgeons and a consultant member of sleep medicine for the American Academy of Otolaryngology.

Rishi Jay Gupta, DDS, MD, MBA, is the section chief, oral and maxillofacial surgery, dental service, at the San Francisco VA Health Care System. He also serves as the regional sleep surgical and dental director for the VA Health Care System. He is assistant professor, department of oral and maxillofacial surgery, at the University of California, San Francisco and practices in a private practice. Dr. Gupta is a fellow of the American College of Surgeons.

Conflict of Interest Disclosure for both authors: None reported.

The origin of sleep surgery is rooted in medicine and dentistry. The late William Dement, MD, PhD, is recognized as the father of sleep medicine. He launched the world’s first sleep disorders clinic at Stanford University Medical Center in 1970. He recruited Christian Guilleminault, MD, DM, DBiol, who is credited with describing obstructive sleep apnea (OSA) as a clinical entity. OSA is characterized by repetitive episodes of complete or partial upper airway obstruction during sleep resulting in disruptions of normal sleep architecture and is associated with arterial desaturations. [1] The prevalence is approximately 11.1% in men and 4.9% in women based on the Sleep Heart Health Study. [2] The sequelae of OSA includes metabolic syndrome, cardiovascular morbidities, neurocognitive deficits, psychosocial consequences and cancer. [3]

Nelson Powell, MD, DDS, a pioneer of sleep surgery, once recounted: In 1979, Dr. Guilleminault and Dr. Dement were interested in Bob Riley and I since we both had maxillofacial and dental experience. They were convinced that children and adults needed a more aggressive approach to obstructive sleep apnea than weight loss or tracheotomy.

At a time when continuous positive airway pressure (CPAP) and oral appliance therapy (OAT) were not yet introduced and tracheostomy was the only surgical solution, [4] Drs. Riley and Powell’s recognition of soft tissue and skeletal targets for OSA treatment was truly novel. [5] They credit their surgical algorithm to a sound foundation in dentistry and, more specifically, in maxillofacial growth and development. They both graduated from the University of California, San Francisco, School of Dentistry. Dr. Powell practiced as a general dentist in the Sacramento area before obtaining his medical degree at the University of Washington. Dr. Riley finished oral surgery residency at the University of California, Los Angeles, before obtaining a medical degree from the University of Alabama at Birmingham. They would then meet again, unbeknownst to each other, as residents of otolaryngology one year apart at Stanford.

At Stanford in the 1980s, Drs. Dement, Guilleminault, Kushida, Riley and Powell laid the foundation for contemporary sleep surgery. A phased approach was developed with two premises: 1) Multilevel surgery for the airway is more effective than surgery at a single level, and 2) sleep study would be obtained after phase 1 surgery before moving to phase 2. The algorithm aimed to prevent unnecessary and excessive surgery.

Phase 1 operations include tonsillectomy, uvulopalatal flap and genioglossus advancement. [6,7] Phase 2 is maxillomandibular advancement (MMA). [8] Efficacy of this surgical approach compared favorably to positive airway pressure (PAP) therapy, especially with the inclusion of MMA. [9] Relapse after the phased approach, if not due to excessive weight gain, was frequently addressed by radiofrequency (RF) treatment of the soft palate, genioglossus muscle and posterior tongue base. Of note, Dr. Powell was also the inventor of radiofrequency (RF) use for patients with OSA. [10,11] The inspiration came from an encounter he had with a urologist, who at the time began to explore the use of RF for benign prostrate hyperplasia.

Updated Sleep Surgery Algorithm: From Reconstruction To Restoration

Today, surgery is on a continuum of care for OSA that readily incorporates medical, dental, pharmacologic and behavioral therapy. The mechanism of OSA is complex. Nonanatomic contributors such as arousal threshold, loop gain and muscle tone are not altered by surgery. Sleep surgery affects the critical negative closing pressure (Pcrit) of the upper airway during sleep. [12] Pcrit describes the negative pressure required to collapse the upper airway during sleep. When successful, upper airway surgery decreases airway collapsibility during sleep. It is important to note that this is the same mechanism of action for effective CPAP, OAT and nonairway surgery (bariatric) for OSA.

When successful, upper airway surgery decreases airway collapsibility during sleep.

Sleep surgery has come a long way in the four decades since the advent of the phased approach by Drs. Riley and Powell. 6 In the last few years, critical updates to the phased approach from Stanford have been published in chapters of several specialty textbooks, including medicine, pulmonology, otolaryngology and maxillofacial surgery ( FIGURE 1). [13–15] The updates improve precision for sleep surgery in the following domains:

■ Phenotyping static and dynamic airway collapse.

■ Identifying new anatomic risk factors, along with their solutions.

■ Incorporating technology that improves safety of existing procedures.

Perhaps even more important than advances on the technical front is the shift in paradigm that sleep surgery is about restoration of function rather than anatomic reconstruction. [16] This is unlike cancer surgery, as an example, where a diseased organ is removed and then reconstructed. Sleep surgery is different. It is aimed to improve function that has complex neurologic and physiologic interaction. Going full circle to the earliest days of sleep surgery, understanding facial and airway growth during development serves as the foundation to restorative sleep surgery.

Sleep Surgery Evaluation

Usually when patients are seen at a sleep surgery clinic, they have already been diagnosed with OSA with a sleep study and have tried CPAP or OAT. They may be seeking alternatives to CPAP or OAT, though sometimes the goal should be to improve their adherence to CPAP and OAT. This is especially true in patients who have comorbidities that are unfavorable for elective surgery.

Important questions to ask during the initial patient encounter may include:

■ Original reason for undergoing sleep study (polysomnography).

■ Source and duration of poor sleep (with associated symptoms during wakefulness and sleep assessed by the Epworth Sleepiness Scale).

■ Self-assessment of nasal breathing (questionnaires such as the NOSE or SCHNOS).

■ Is there a history of orthodontic treatment? Use of functional appliance? Use of palatal expanders? Head gear? And at what age?

■ Elicit the goals of treatment: Is it to replace or augment CPAP or OAT use?

■ Desired approach to surgery: do a little bit at a time and seek gradual improvement or start with more invasive procedures?

OSA diagnosis is made with an attended or ambulatory polysomnography (PSG). Ambulatory PSG may underestimate OSA severity in some instances, such as patients with upper airway resistance syndrome (UARS). [17–19] There are myriad ways that one can screen for OSA, from mobile apps to imaging modalities. However, the PSG remains the only diagnostic examination for OSA.

The severity of OSA is measured by the Apnea Hypopnea Index (AHI), and it is the key criteria used by third-party payers to authorize procedures. Oxygen desaturation nadir and the desaturation index (ODI) correlate more strongly with cardiovascular morbidity. [20,21] PSG provides valuable information including the composition of apneas and hypopneas in the overall AHI. Positional OSA can also be assessed. Supine AHI tends to be worse, and some patients may have significant resolution in the lateral position. AHI that is stage dependent also warrants attention, especially in patients whose index greatly increases during rapid eye movement (REM) sleep. This is information that can be gleaned from a PSG report. However, clinicians need to refrain from focusing solely on the AHI. Of note, the definition of hypopnea has changed over the years, and it has evolved to be more inclusive of partial airway closure. Hence, treatment outcome is ideally compared using the same diagnostic study and hypopnea criteria. [22] Recently, there has been greater awareness that solely using the AHI may be inadequate in diagnosing and treating women with sleep surgery. [23]

Imaging

Characterizing the upper airway is important, though the challenge remains that the airway cannot be visualized during sleep. The following is a short review of imaging modalities used for OSA care based on studies with the highest level of evidence.

Cephalometry is widely available and inexpensive. Some measurements of the facial skeleton are highly associated with OSA. [24] Adult patients with OSA are more likely to have maxillary and mandibular deficiency, increased lower anterior facial height and lower hyoid bone. Maxillary deficiency can be assessed by the sella, nasion and point A (SNA) angle. Mandibular deficiency can be assessed by the sella, nasion, point B (SNB) angle and the mandibular plane, which is measured from gonion to gnathion (Go-Gn). Increased distance between the mandibular plane and the hyoid (MP-H) is consistent in adult patients with OSA. Lower anterior facial height, defined as the distance between the anterior nasal spine to the gnathion, is also a risk factor for adult OSA.

There is widespread interest in using cone beam computed tomography (CBCT) for airway evaluation. It has the benefits of volumetric assessment of the airway from a 3D standpoint. A systematic review of observational studies concludes that discrepancies in the technique of imaging acquisition limit the utility of their evaluation. [25] Most studies did not control for respiratory phase, mandibular position or tongue position, which all influence airway dimensions. Another limitation is patient positioning, as most CBCT scanners provide imaging acquisition in the upright position. Airway cross-sectional area is reduced when changing from the upright to the supine position. This change is largely attributed to changes in the position of the hyoid bone, the mandible, the tongue and upper airway muscles. Conclusions from upright CBCT cannot be readily applied to supine cross-sectional imaging. In a systematic review, the most significant anatomical characteristic related to the diagnosis of OSA is the small crosssectional area of the airway (CSAmin). [26]

Besides cephalometry and CBCT, upper airway anatomy can be assessed by somnofluroscopy, conventional computed tomography (CT), cine CT (ultrafast CT), magnetic resonance imaging (MRI), cine MRI (ultrafast MRI) and ultrasonography. These imaging modalities have limitations preventing widespread utility. Somnofluroscopy distinguishes snoring from apneas, but the high radiation exposure and poor anatomical detail limit its utility. Cine CT overcomes the limitations of static examination by CBCT and conventional CT, though patients are exposed to excessive radiation. Drug-induced sleep cine CT proved effective in identifying the level of obstruction. [27] However, it has limited use due to expense, sedation requirements and potential airway complications. Sleep MRI provides dynamic evaluation with greater soft tissue detail. In a nested case control study, sleep MRI identified lateral pharyngeal wall collapse and hyoid position to correlate with severity of OSA. [28] Ultrasonography is emerging as a promising modality in screening. It has the advantages of low cost utility in clinic examination and no radiation. In summary, use of cephalometry and CBCT is practical. The current body of evidence supports their use as screening tools for surgical decision-making.

Nasopharyngoscopy and Drug- Induced Sedation/Sleep Endoscopy

Another way to “see” the airway is to use fiberoptic endoscopy. Routine examination involves the Muller maneuver (MM). MM consists of having the patient perform a forced inspiratory effort against an obstructed airway with fiberoptic nasopharyngoscopy. Airway collapse as a result of the negative pressure maneuver is assessed at the soft palate, lateral pharyngeal wall and base of the tongue. Grading is on a 5-point scale, with 0 being no collapse and 4 being complete collapse. MM is widely used by clinicians. It is easy to perform, allows exclusion of other lesions and has validity when significant collapse is present. It has a high degree of reliability between raters, regardless of experience, and a modest correlation with preoperative AHI. [29] A mandibular protrusion maneuver can also be performed to assess the degree of lateral pharyngeal wall expansion. In patients where mandibular protrusion greatly opens the hypopharynx, OAT can be favorable. [30]

Airway visualization has been augmented with drug-induced sedation (sleep) endoscopy (DISE). [31,32] The procedure is usually performed in an outpatient surgery setting with monitoring of oxygen saturation, heart rate, blood pressure and, sometimes, bispectral index score (BIS). Propofol, dexmedetomidine and midazolam are commonly used for induction of sedation. Propofol has the benefit of rapid onset of action and recovery with minimal side effects. [33] Midazolam has a greater therapeutic range but is limited by its slow onset and potential to cause respiratory depression. Dexmedetomidine has the characteristics of rapid onset and small therapeutic range with less respiratory side effects. [34] The depth of sedation is critical and evaluated by the onset of disordered breathing or the BIS. [35]

Several classification systems have been introduced to characterize DISE findings. [36–40] The VOTE classification system, comprised of the velum, oropharyngeal (lateral walls), tongue and epiglottis, is widely used (FIGURE 2). The most common finding from DISE of OSA patients is multilevel collapse, despite heterogeneity among studies. [41,42] With respect to evaluation of sleep surgery outcome, DISE findings of lateral pharyngeal wall collapse predict better response with MMA as compared to soft tissue surgery. [43–45] DISE is also part of the workup for candidacy of hypoglossal nerve stimulation (HNS). [46]

How Is the New Algorithm Used?

Efficacy of upper airway surgery for OSA begins to drop as BMI increases. Current guideline for HNS, for example, discourages use in patients with a BMI greater than 32 kg/m 2 . Bariatric surgical evaluation and treatment should precede upper airway surgery in select candidates. Otherwise, the first decision is made regarding optimization of PAP or OAT. Nasal obstruction may be the main cause of PAP intolerance. [47,48] Therefore, care should be taken to assess anatomical abnormalities causing nasal obstruction including posterior septal deviation [49,50] ( FIGURE 3). The exam should involve endoscopic examination to identify all possible anatomic and functional causes of nasal obstruction. [51] Nasal examination is not limited to the nasal passages alone. Long-term nasal obstruction leads to facial changes, most often in the appearance of a long midface, open bite and retruded mandible. Intraoral examination may show a narrow, high-arch maxilla with the relative appearance of a large tongue and redundant soft palatal tissue. This is the classic adenoid facies associated with chronic mouth breathing. [52–54]

Summary of Surgical Procedures by Site of Action

Intranasal Surgery: Septoplasty, Inferior Turbinate Reduction, Nasal Valve Grafts or Stabilization

Nasal breathing is important for sleep quality, and nasal obstruction contributes to the pathogenesis of OSA. [55,56] Septal deviation, inferior turbinate hypertrophy and internal nasal valve dysfunction can result in increased nasal resistance and mouth breathing. Increased nasal resistance leads to downstream inspiratory collapse of the oropharynx or hypopharynx in susceptible patients. [57,58] Mouth breathing can also cause posterior displacement of the base of the tongue and narrowing of the hypopharyngeal airway. [59] Nasal surgery including septoplasty, turbinoplasty or valve reconstruction can restore nasal airway patency and reduce nasal resistance and mouth breathing. Although nasal surgery alone shows inconsistent efficacy based on the AHI, [60] it improves sleep quality, OSA-related sleep symptoms and PAP compliance. [61–63] Nasal surgery is important as part of the multilevel treatment plan for OSA. [64]

“Rhino-gnathic” Surgery: Distraction Osteogenesis Maxillary Expansion (DOME)

Expansion of the adult nasal floor is useful for OSA patients who present with nasal obstruction and narrow, high-arch maxilla. 54 Patients with this phenotype tend to struggle with both nasal obstruction and lack of intraoral volume for the tongue during sleep. This means poor nasal breathing while awake and asleep. Maxillary expansion directed at the nasal floor by distraction osteogenesis with maxillary expansion (DOME) has shown promise in adults with OSA [65–68] ( FIGURE 4 ). Minimally invasive osteotomies can be made at the Le Fort I level via an intranasal incision with endoscopic visualization ( FIGURE 5). An expander is anchored to the roof of the maxilla intraorally ( FIGURE 6). The patient turns the expander once a day for a month, which generally results in 8 mm to 10 mm of widened nasal floor at the internal nasal valve (INV). Orthodontic treatment using traditional braces or clear aligners are then used to restore occlusion. Conceptually similar to pediatric rapid maxillary expansion, DOME effectively addresses the same anatomic phenotype in adults. [68–72] The INV is the most restrictive part for nasal airflow and is a primary target for intervention by DOME.

Oropharynx: Tonsillectomy With Pharyngoplasty (Uvulopalatopharyngoplasty)

Uvulopalatopharyngoplasty (UPPP) remains the most commonly performed sleep surgical procedure worldwide. [73] Most surgeons specializing in OSA have evolved from earlier methods of UPPP, which tend to be ablative including resection of the uvula and parts of the palatopharyngeus and palatoglossus muscles. Procedures such as the laserassisted uvulopalatopharyngoplasty (LAUP), for example, which worsens AHI in 44% of patients, are no longer recommended. [74]

Isolated UPPP is reported to have a success rate of 41% in all-comers. [75] Isolated UPPP is most successful in Friedman stage I patients. 38 These are patients who have large tonsils, a small tongue and most of the soft palate visualized. However, these patients are rarely encountered in a surgical practice. Generally, patients are seen with the modified Mallampati IV tongue position with endophytic but large palatine tonsils ( FIGURE 7).

In clinical practice, various forms of UPPP are performed as part of multilevel surgery to maximize surgical success. [6,76,77] In the Riley-Powell sleep surgery algorithm, uvulopalatal flap with genioglossus advancement comprises phase 1. The uvulopalatal flap was designed as a reversible soft palate procedure in the event of velopharyngeal insufficiency. 7 Most forms of contemporary UPPP focus on palatal muscle expansion and stabilization with targeted vectors during suturing. [78–81]

A recently described indication for isolated UPPP precedes hypoglossal nerve stimulation (HNS). Complete concentric collapse of the soft palate (velum) seen during DISE is an exclusion criterion for HNS. UPPP can reverse this collapse pattern and allows more patients to be candidates for HNS [82] ( FIGURE 8 ).

Tongue Base: Lingual Tonsillectomy

Lingual tonsillar hypertrophy can be a cause of retrolingual obstruction and surgical failure. [83] Removal of the lingual tonsils and base of tongue fat may involve the use of coblation, laser or robotic assistance per surgeon preference. [84–86] The removal of tissue in this area can be supplemented by an anterior anchorage of the epiglottis to the base of tongue in the setting of epiglottis collapse. With high-quality optics for improved visualization and instrumentation, robotics were adapted and introduced to target the posterior tongue. [86,87]

While transoral robotic surgery (TORS) offers unparalleled visualization, the use of multiarmed robots designed for the abdominal cavity is cumbersome for the upper airway. Results for the use of TORS as part of a multilevel surgical approach for OSA are promising for select patients. Success rate of TORS was higher than 75% in nonobese patients and 50% in obese patients with OSA. [88] The cost and morbidity may be greater than with other techniques offsetting its advantages in visualization and precision. [89] A single-port robot system designed for single cavity operative sites is promising. [90] Augmented reality-assisted TORS using a single-port robot will reduce bleeding and increase precision in distinguishing fat from muscle [91] ( FIGURE 9).

Tongue Muscle Strengthening: Genioglossus Advancement

Classic genioglossus advancement (GA) was designed by Powell and Riley as part of the phase 1 algorithm. GA is usually performed in conjunction with other procedures (UPPP, MMA). [92] The genioglossus muscle, a powerful dilator muscle of the upper airway, is attached to the genial tubercles. In advancing the genial tubercles, the genioglossus muscle strengthens over time and allows greater tongue advancement during sleep. [93] With the wide availability of CT imaging, virtual surgical planning (VSP) and osteotomy guides allow contemporary GA to be considerably more precise [94] ( FIGURE 10 ). GA and genioplasty can often be performed in conjunction to improve facial balance in retrognathic patients. [95] This combination also strengthens suprahyoid muscles. VSP allows each patient to have a tailor-made GA, genioplasty or their combination.

Tongue: Hypoglossal Nerve Stimulation

At the time of publication, there is only one FDA-approved hypoglossal nerve stimulation (HNS) device (Inspire Medical Systems Inc., Maple Grove, Minn.) for OSA ( FIGURES 11 and 12). It generates a unilateral respirationsynchronized stimulation of the medial hypoglossal nerve branches and C1 nerve via the genioglossus and geniohyoid muscles leading to tongue stiffening and protrusion. The hypoglossal nerve (CN XII) innervates both the tongue protrusor (genioglossus) and retrusor (styloglossus and hyoglossus) muscles through its medial and lateral divisions. Selective stimulation of the protrusor muscles leads to anterior movement of the tongue, resulting in increased airflow and reduced pharyngeal collapse during sleep. [96] ( FIGURE 13). Selective stimulation of the deep and horizontally oriented genioglossus fibers results in curling and stiffening of the tongue, further expanding the upper airway. [97]

The current selection criteria require DISE to rule out complete concentric collapse of the velum. There is a BMI ceiling of 32 kg/m 2 and an AHI range from 15 to 65 events per hour. There is also a 25% cutoff for central apneas. Implanted patients undergo in-lab titration of HNS approximately two months after implantation.

The STAR trial shows HNS to be successful with a median decrease of 68% in AHI. [98] Recent meta-analyses show that HNS is safe and effective for selected patients with moderate to severe OSA. [99] HNS can improve AHI as well as sleep architecture in responders. Arousal index and N1 stage sleep were reduced while N2 stage and slow-wave sleep increased after HNS. There were no significant changes to REM sleep. [100]

Total Upper Airway — MMA

MMA was pioneered by Riley and Powell at Stanford Hospital in the late 1980s and addresses the entire upper airway implicated in OSA. It remains one of the most effective surgical interventions for patients with OSA and has compared favorably to CPAP in a variety of studies including a prospective, randomized controlled trial. [6,8,9,93,101–104] MMA involves osteotomies of the maxilla and mandible, followed by their advancement that is frequently accompanied by a counterclockwise rotation [105,106] ( FIGURE 14 ). The net effect includes greater volume for intraoral soft tissue structures and stability of the upper airway dilator muscles [107–110] ( FIGURE 15).

It is important to note that MMA is not simply “orthognathic surgery” where jaws are moved forward. Orthognathic surgery is the use of skeletal movements to treat a skeletal problem (malocclusion and jaw asymmetry or discrepancy). MMA is where skeletal movements are used to treat a soft tissue problem (airway). That said, one certainly needs to have orthognathic considerations when designing MMA movements. However, Angle Class 1, 2 and 3 patients can all be advanced for airway purposes, with rotations designed differently to optimize facial balance and aesthetics.

Generally, indications for MMA are moderate to severe OSA with or without history of phase 1 surgery; OSA of all severity with comorbid dentofacial deformity; and concentric and lateral pharyngeal wall collapse seen during DISE. [14,106,110,111] The patterns of CCC, multilevel collapse and tongue base collapse are associated with higher AHI. [41,42] CCC of the velum is associated with poor surgical outcomes in multilevel soft tissue surgery and HNS, [112,113] but it is well-addressed by MMA. [108]

Meta-analysis by Holty, et al. examined 22 studies involving 627 patients who underwent MMA, reporting mean AHI decrease from 63.9 to 9.5 events per hour. The authors defined surgical success with the Sher criteria: a minimum of 50% reduction with a final AHI less than 20. The surgical success rate was 86.0% and the cure rate (AHI < 5) was 43.2%. The predictive factors for surgical success were younger age, lower BMI and greater degree of maxillary advancement [114] ( FIGURE 16). The major and minor complication rates were 1.0% and 3.1%, respectively. Age at time of surgery and severity of OSA have not been shown to negatively impact the technical challenges of MMA in a high-volume center. [115] An updated metaanalysis with 45 studies and 528 patients reports success and cure rates of 85.5% and 38%, respectively. [116] In 40 patients who underwent MMA with average follow-up of 4.2 years (range, one to 12 years), 36 (90%) patients maintained a significant reduction in RDI from 71.2 to 7.6 events per hour with improvement in daytime sleepiness. [117] In another study with a mean follow-up of 12.5 years, the surgical success rate maintained at 100% in patients younger than 45 and who had BMI less than 25 kg/m 2 . [118]

Beyond the AHI, MMA has shown normalization of sleep architecture (increase in REM sleep and decrease in wakefulness after sleep onset) when compared to age-matched healthy controls. 46 It has also shown improvements in multiple health-related and functional outcomes. [119]

Special Clinical Consideration: OSA and Temporomandibular Derangement

The association between temporomandibular derangement (TMD) and sleep OSA is welldocumented although Mthe underlying mechanisms at the central level remain poorly understood. TMD often leads to sleep fragmentation and respiratory effort-related arousal events, [120–122] which are associated with nocturnal bruxism and chronic pain. Chronic bruxism leads to dental wear and trauma, TMD pain, condylar resorption and internal disc derangement. The arousals due to apneic events may be driving the sympathetic system that leads to bruxism. OAT can be used to treat both OSA and TMD. [123–125] All patients who present with either bruxism and associated TMD or OSA should be screened for their comorbidity. Nightguards that increase vertical dimension of occlusion (VDO) can lead to worsening of OSA symptoms due to the clockwise rotation of the mandible. [126–128] As a result, patients treated with nightguards for TMD should try to minimize the VDO due to effects on OSA. Further, close monitoring is critical in patients treated with OAT, as it can cause occlusal changes and worsening of TMD symptoms such as pain and anatomic pathology. [129,130]

Patients with chronic TMD tend to be retrognathic and experience loss of posterior vertical height over time, contributing to a more collapsible airway due to progressive retrusion. [131,132] Clinical experience and data have long supported the notion that patients with OSA who are intolerant of PAP therapy can undergo MMA with high success rates. [133,134] However, there is a subset of OSA patients who also present with TMD. Proceeding with MMA without addressing preexisting TMD may lead to joint instability and subsequent condylar resorption with skeletal relapse. [135,136]

Temporomandibular joint reconstruction (TJR) utilizing custom prostheses has been well documented in treating TMD and can be performed in conjunction with MMA to improve facial aesthetics, mastication, airway and pain. [137] Bilateral TJR with concomitant MMA surgery is a solution that allows surgeons to treat both TMD and OSA [138–144] ( FIGURE 17).

Special Clinical Consideration: Severe OSA Treated With Combination MMA and HNS

MMA and HNS are effective surgical options for the treatment of OSA. Both have shown predictably high success rates with low morbidity in well-selected candidates. They differ in strengths and limitations and may complement each other. They share similarity as “extrapharyngeal” operations, meaning they do not intervene on the airway muscles directly. [145] UPPP or tongue base reduction, for example, would be “intrapharyngeal.” In fact, MMA, HNS, CPAP and OAT are all examples of extrapharyngeal interventions. HNS following MMA relapse is a safe and effective option especially in patients with advanced age. 146 Patients with significantly elevated AHI can be planned for MMA and HNS together.

Summary

Surgical management of OSA has improved with growing understanding of the condition’s pathophysiology, new methods of airway phenotyping and precision in operative techniques. The classic phased approach serves as a foundation for the current algorithm, which places surgery on a continuum with medical and dental care. This is important not only from the perspective of precision medicine, but also for patientcentric needs. After all, these are elective operations, and the patient ultimately decides on proceeding with recommended procedures. With the new algorithm, there is greater emphasis on collaboration with all medical and dental colleagues when taking care of OSA patients. The goal of treatment is not merely in the reduction of AHI but addressing the symptoms and sequelae of associated comorbidities.

Prevention strategy such as guiding proper facial and airway development during growth will remain at the forefront of research. This is where all dental colleagues can help. The last 40 years have seen a burgeoning of effort focused on individual surgical or dental success rates. What lies ahead should be a focus on improving overall treatment success, usually achievable only with multi-modal treatments. The goal for treatment success of the OSA patient will foster collaboration across disciplines. As this year celebrates the 40th anniversary of the world’s first sleep center, we are in a better position than ever to optimize everyone’s sleep and dreams.

ACKNOWLEDGMENT

Liu: I thank my mentors, fellows and research scholars who have all made significant contributions to my understanding of sleep surgery. Moreover, their friendship has allowed me to develop both as a surgeon and a person. For this article, Corissa Chang, DDS, and Ahmed AlSayed, MD, are recognized for their review of the imaging section. Lastly, to Bob and Nelson: It is your legacy that allows all of us to stand on the shoulders of giants.

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THE CORRESPONDING AUTHOR, Stanley Yung- Chuan Liu, MD, DDS, can be reached at ycliu@stanford.edu.