OVERVIEW OF ADULT SLEEP APNEA SURGERY

Kasey K. Li, MD, DDS, FACS

INTRODUCTION 

Obstructive sleep apnea syndrome is the result of upper airway obstruction from repetitive airway narrowing and closure during sleep. It is associated with increased cardiovascular morbidity and mortality.^1,2  The psychomotor sequelae of obstructive sleep apnea, such as excessive daytime sleepiness, daytime fatigue and poor sleep quality due to sleep fragmentation, are also well established. ^3,4  Currently, nasal continuous positive airway pressure (CPAP) is the first line of treatment. Indeed, the effectiveness of nasal CPAP in improving the sequelae of obstructive sleep apnea is irrefutable. ^5,6  Nevertheless, patient compliance represents a clear problem. ⁷  Furthermore, even in compliant patients who are using CPAP on a “regular basis,” the actual usage is only approximately 50% of the ideal.⁸   Due to the limitations of CPAP, surgical treatment of OSA should be considered as a viable treatment option.  

This review will present the current state of art in sleep apnea surgery, beginning with evaluation of the patient as surgical candidate to formulation of a surgical plan through procedural selection based on published surgical outcomes. 

PRE-OPERATIVE  ASSESSMENT

Numerous surgical procedures are currently available for the treatment of obstructive sleep apnea. However, the following issues present a formidable challenge to the sleep apnea surgeon: 1) the complex interplay of the soft and hard tissues that contribute to upper airway obstruction; 2) the crucial role of this anatomic region to speech and swallowing; and 3) the subsequent edematous response after surgical intervention. Moreover, it is well accepted that successful surgical outcomes depend on proper patient selection as well as the choice of surgical procedure(s). Therefore, a logical and systematic approach to clinical evaluation, treatment planning, surgical execution and perioperative management is necessary to maximize safety and improve outcomes.

Clinical evaluation must include the overall body habitus (height, weight and neck circumference), since it has been shown that surgical outcomes can be influenced by these factors. ⁹  Obviously, a detailed examination should focus on the head and neck region in order to identify the potential sites of upper airway obstruction, including the nose, soft palate, lateral pharyngeal walls and tongue base. The presence of nasal septal deviation, turbinate hypertrophy, nasal valve collapse, elongation of the soft palate/uvula, tonsillar hypertrophy, enlargement of the tongue, narrowed and/or deficient maxilla and mandible are many of the common findings in patients with obstructive sleep apnea. By using fiberoptic nasopharyngoscopy and lateral cephalometry along with direct visual examination, the upper airway can be completely assessed for anatomic abnormalities that may be contributing to obstructive sleep apnea.

Airway examination by a fiberoptic scope is highly recommended in patients with obstructive sleep apnea. This evaluation enables the examiner to directly visualize the entire upper airway from the nose to the larynx.  The dimension of the nasal, velopharyngeal and hypopharyngeal airway can be fully assessed. Furthermore, the prominence of the tongue base and the lateral pharyngeal wall, as well as their collapsibility, can be evaluated with the Muller’s maneuver. ¹⁰ 

Lateral Cephalometric Radiograph

Many airway imaging methods are currently available.  Computed tomography (CT) or magnetic resonance (MR) can precisely assess the dimension of the upper airway. ^11,12  However, due to cost constraints, none can be widely used in clinical practice except the lateral cephalometric radiograph.  Although lateral cephalometric radiograph is only a static two-dimensional method of evaluating a dynamic three-dimensional area, it is a valuable study in identifying abnormal facial skeletal anatomy that may contribute to airway obstruction as well as the relation of the hard and soft tissues of the airway.  Furthermore, lateral cephalometric radiograph provides useful information on the posterior airway space behind the soft palate and the tongue base.  The posterior airway space measurement on lateral cephalometric radiograph has been shown to correlate with the volume of hypopharyngeal airway on three-dimensional CT scans. ¹³   

SURGICAL PROCEDURES

Nasal Surgery

The relationship between nasal obstruction and sleep-disordered breathing has been demonstrated by numerous investigations. Both daytime nasal obstruction and nocturnal nasal congestion have been shown as risk factors for sleep-disordered breathing.^14,15 Therefore, the treatment of nasal obstruction plays an important role in sleep apnea surgery.  However, it must be emphasized that although obstructive sleep apnea can be improved in some patients, only slight improvement has been shown.^16,17  Three anatomic areas of the nose that may contribute to obstruction are the alar cartilage/nasal valve region, the septum and the turbinates. The most common nasal surgical procedure consists of septoplasty and turbinate reduction. The major effects of nasal surgery are subjective improvement of nasal patency and reduction of the nasal CPAP requirement.^16,17

Uvulopalatopharyngoplsty

Uvulopalatopharyngoplasty has been the most common sleep apnea surgical procedure performed during the past 25 years.¹⁸  Traditional uvulopalatopharyngoplasty procedure consists of the removal of redundant soft palate and pharyngeal tissues as well as uvula, so as to widen the oropharyngeal inlet.  The tonsillar tissues are also removed if present.  Although uvulopalatopharyngoplasty can significantly improve oropharyngeal obstruction, hypopharyngeal obstruction is minimally affected by the procedure, thereby reflecting a success rate of only approximately 40%. ¹⁹  Furthermore, potential complications including velopharyngeal insufficiency, stenosis and dysphagia are major concerns.  Consequently, several modifications of the traditional procedure have been developed to improve outcomes and reduce complications.

Uvulopalatal Flap

The uvulopalatal flap procedure is a modification of uvulopalatopharyngoplasty, which results in the widening of the oropharyngeal airway by suspension of the uvula superiorly toward the hard-soft palate junction after a limited resection of the uvula, lateral pharyngeal wall and the mucosa. ²⁰  As such, this surgical technique results in the widening of the oropharyngeal airway. A prospective study of 80 patients with variables including age, sex, body mass index, soft palatal length, respiratory disturbance index (RDI), lowest oxygen desaturation (LSAT) and subjective snoring scale demonstrated that there was no statistical significant difference between the uvulopalatal flap group and the uvulopalatopharyngoplasty group.  Using a visual analog scale to assess pain, there was significantly less pain in the uvulopalatal flap group vs. the uvulopalatopharyngoplasty group.

Pharyngoplasty

The pharyngoplasty procedure is another modification of the uvulopalatopharyngoplasty. This procedure usually involves the removal of tonsillar tissues, but the uvula and the soft palate is preserved.  The pharyngeal inlet is widened and the airway collapsibility is reduced purely via suturing of the tonsillar wounds.  This procedure represents the most conservative pharyngeal surgery and has minimal side effects as compared to other procedures.  This is the preferred procedure by the author.

Laser-Assisted Uvulopalatoplasty

Laser-Assisted Uvulopalatoplasty (LAUP) was introduced by Kamimi as an office-based surgical procedure for the treatment of snoring. ²¹  The procedure involves removal of the uvula and a portion of the soft palate by carbon dioxide laser incisions and vaporization.  Most of the uvula is amputated, and the soft palate (1-2 cm lateral to the uvula) is incised and vaporized.  Additionally, mucosal or tonsillar pillar tissue is vaporized as needed. 

Although many studies have evaluated the efficacy of LAUP in the treatment of OSA, most of the studies are flawed by methodological discrepancies or statistical inadequacies such as ill-defined criteria for response and lack of adequate follow-up.  In addition, LAUP is associated with increased risk of dysphagia as well as the risk of discontinuation of treatment due to pain. ^22,23  Moreover, recent AASM evidence-based guidelines do not support the use of LAUP in the treatment of obstructive sleep apnea. ²⁴

Genioglossus Advancement 

The mandible and the tongue are major determinants of the airway dimension.  Anterior positioning of these structures has been shown to improve obstructive sleep apnea. The genioglossus advancement procedure is limited to moving forward the geniotubercle with the genioglossus insertion without moving the mandible. This advancement places tension on the tongue musculature, thereby limiting the posterior displacement during sleep.  The genioglossus advancement procedure consists of a rectangular osteotomy on the symphysis of the mandible intraorally. The rectangle is advanced forward by the thickness of the mandible and partially rotated to prevent retraction back into the floor of the mouth.  Incorporation of the geniotubercle during the procedure has been shown to be quite successful with this technique. ²⁵  In general, genioglossus advancement is performed with other sleep apnea surgical procedures such as UPPP and hyoid advancement in order to maximize improvement.  The results from these procedures have been variable, ranging from 23% to 77%. ^26-29  These variable results underline the difficulty in accurately predicting the success rate.  Clearly, anatomic factors, body habitus and obstructive sleep apnea severity are all factors that influence surgical success.  In general, the potential risks associated with genioglossus advancement are quite limited, including infection, hematoma, injury to the genioglossus muscle and paresthesia of the lower teeth.

Hyoid Advancement

The hyoid bone holds an intimate relationship with the tongue base and pharyngeal musculature, thus portraying an integral aspect of the upper airway anatomy.  The hyoid bone may be surgically repositioned anteriorly by attaching it to the thyroid cartilage in order to expand the airway. ³⁰  The procedure is usually performed in conjunction with genioglossus advancement so as to contribute to the improvement of obstructive sleep apnea. ^{28,29, 31}  However, some surgeons have elected to combine it with UPPP alone. ³²   An inherent problem with hyoid advancement is the requirement of an external incision on the neck, one aspect that may not be readily accepted by all patients.  As with other sleep apnea surgical procedures, the results of hyoid advancement are variable, ranging from 23% to 65%. ^28-31 In general, the associated surgical risks are low, and may include infection, seroma formation and dysphagia.

Maxillomandibular Advancement 

Abnormality of the maxillofacial skeleton is a well-recognized risk factor of obstructive sleep apnea. ^18,19  Maxillomandibular advancement was initially advocated based on the finding that maxillofacial skeletal abnormality (i.e., maxillary and/or mandibular deficiency) is frequently found in patients with obstructive sleep apnea, and that maxillomandibular deficiency results in diminished airway dimension, which leads to nocturnal obstruction.  Maxillomandibular advancement achieves enlargement of the entire upper airway including the nasal, pharyngeal and hypopharyngeal airway expansions of the skeletal framework that encircle the airway.  Comparison of pre- and post-operative airway appearance based on fiberoptic nasopharyngoscopy and lateral cephalometric radiograph have demonstrated that in addition to airway expansion by the forward movement of the maxillomandibular complex, the tension and collapsibility of the suprahyoid and velopharyngeal musculature may also be reduced, thus leading to the reduction of lateral pharyngeal wall collapse. ³³ 

The maxillomandibular advancement procedure consists of mobilizing the maxilla and mandible to achieve anterior displacement of the maxillomandibular complex after intraoral osteotomy of the maxilla and mandible.  The maxilla and mandible are stabilized with titanium plates in the advanced position.  In order to maximize the airway expansion, an advancement of 10-12 mm is usually recommended.  However, it is important to achieve maximal advancement while maintaining a stable dental occlusion as well as balanced aesthetic appearance.  Interestingly, although many patients may be left with “prominent jaws,” very few of them are dissatisfied with their appearance. ³⁴

Maxillomandibular advancement is the most effective sleep apnea surgical procedure currently available. The success rate is usually between 75% and 100% ^27,28,35,36 with a long-term success rate approaching 90%.^37,38  In addition, patient perception of the surgical outcome has been very favorable. ³⁵  Although maxillomandibular advancement is considered a fairly invasive procedure, the associated surgical risks are low, including bleeding, infection, malocclusion and permanent numbness.

Maxillomandibular Expansion

A constricted maxilla with a high and narrowed hard palate contributes to increased nasal resistance^39-41 and is a common finding in patients with obstructive sleep apnea. ^42,43  Investigators have demonstrated that expansion of the maxilla can improve obstructive sleep apnea in children and adolescents as well as adults. ^44,45  Furthermore, since patients with maxillary constriction often have a corresponding mandibular constriction, expansion of the maxillary and mandibular complex has also been shown to be beneficial in reducing the severity of obstructive sleep apnea. ⁴⁶  The procedure consists of limited osteotomies to allow widening of the maxilla and mandible with distractors.  The advantage of maxillomandibular expansion is that it is considerably less invasive than maxillomandibular advancement.  However, treatment time is lengthened and patients need to keep the distractors in place for several months after the operation to ensure that the expansion is stable.  Therefore, patient acceptance for this treatment option may be affected.  In addition, orthodontic therapy is also mandatory and may possibly influence patient acceptance of this treatment modality.

Temperature-Controlled Radiofrequency Tongue Base Reduction

Low-wave radiofrequency energy achieves therapeutic ablation of tissue in a minimally invasive fashion.  Radiofrequency can be safely applied to the upper airway tissue to improve OSA by volumetric tissue reduction and tissue stiffening.

Current radiofrequency energy delivery to the upper airway tissue occurs through a needle electrode.  The energy current causes ionic agitation of the tissue around the electrode, resulting in frictional heating of the tissue.  Therefore, the electrode itself does not get hot; heat actually emanates from the tissue.  Tissue injury occurs when the temperature reaches beyond 47°C, which is when cell proteins undergo denaturation. The size of the lesion (area of tissue injury) created on the tongue is dependent on the current intensity and the duration of energy delivery. ⁴⁷  Typically, the lesion is in the shape of an ellipse, with the long axis of the lesion approximating two times the length of the needle electrode and the transverse axis approximating two-thirds of the long axis.

Since the radiofrequency energy disbursement is proportional to 1/radius⁴, heat dissipation is limited and excessive tissue injury is minimized.  Furthermore, when the temperature reaches 90-100°C, char formation on the electrode leads to an increase in impedance and results in disruption of current flow, thus serving as a second layer of protection. These factors allow radiofrequency ablation to create a predictable tissue injury pattern, thereby minimizing potential complications.  

The first prospective study of radiofrequency tongue reduction was conducted in 18 patients. ⁴⁸  After a mean total energy of 8490 joules was delivered per patient over a mean of 5.5 treatments, the mean RDI improved from 39.6 to 17.8 with an improved LSAT from 81.9% to 88.3%.  The tongue volume was reduced by a mean of 17% (based on MRI findings).  There were no changes in speech or swallowing. Complications included a superficial tongue ulceration that resolved spontaneously, persistent pain on swallowing that resolved after several weeks, and a tongue abscess that required drainage.  Sixteen of the 18 patients were followed on a long-term basis (mean of 28 ± 4 months). ⁴⁹  Findings demonstrated a mean weight increase of 3.1 ± 7.9 kg.  In addition, there was a worsening of RDI from 17.8 to 28.7.  There was also a worsening trend in the LSAT from 88.1% to 85.8%.  However, there was no significant deterioration of the quality of life measurements by SF-36 or daytime sleepiness by Epworth Sleepiness Scale (ESS). 

Multiple other reports have shown radiofrequency tongue reduction to be efficacious in improving obstructive sleep apnea. ^50-52  However, based on all reports, improvement with radiofrequency tongue reduction is insufficient as a single treatment modality.  Therefore, it should most likely be considered as an adjunctive treatment in combination with other surgical approaches.

Tracheostomy

The use of tracheostomy to bypass upper airway obstruction in “Pickwickian” patients was the first reported treatment for obstructive sleep apnea.⁵³  Despite being the most effective treatment for obstructive sleep apnea, patient acceptance is low due to the associated morbidity and social implications. The current use of tracheostomy primarily serves as a temporary measure for airway protection in patients with severe sleep apnea with either morbid obesity or significant craniofacial anomalies that pose a high risk for airway compromise in the perioperative period. ^54,55  However, permanent tracheostomy as a long-term treatment of obstructive sleep apnea remains an option in morbidly obese patients with obesity hypoventilation syndrome or in patients with significant craniofacial anomaly who have failed all other forms of non-surgical and surgical treatments. ^56-58

SURGICAL PLANNING

Clearly, prior to any sleep apnea surgery, the diagnosis of obstructive sleep apnea based on sleep study results is essential.  Although some may debate whether a formal polysomnography should be mandatory, the use of an ambulatory sleep study is an acceptable practice under current standards.   The selection of surgical procedure(s) is based on numerous factors (Table 1).  The patient’s desire and preference as well as the health status can clearly influence outcomes and must be taken into consideration. Additionally, the goal of surgery may be different for patients.  Although the majority elect surgical treatment due to intolerance of non-surgical treatments, some patients may consider surgery in order to improve their ability to tolerate non-surgical treatments, such as the reduction of therapeutic CPAP pressure or improvement of nasal symptoms due to CPAP use.  Therefore, the surgical endpoint should be discussed prior to surgery, along with criteria for surgical success (Table 2).  Informed consent must be conducted, and patients should be educated regarding the rationale of surgery as well as associated risks and benefits. 

In formulating a surgical plan, the most difficult task for the surgeon is to decide which procedure(s) should be utilized.  Indeed, information gathered from the pre-operative assessment including clinical examination, fiberoptic nasopharyngoscopy and lateral cephalometric radiograph can provide useful information regarding the upper airway anatomy and the site(s) of obstruction.  Nevertheless, the only surgical procedure that has been able to achieve a consistently significant response rate is maxillomandibular advancement.  Other surgical procedures that are less invasive are often much less predictable and clearly less successful, especially in patients with severe obstructive sleep apnea.  Thus, as the severity of the obstructive sleep apnea increases, so will the invasiveness of the procedures needed to achieve improvement.

Clearly, the most logical surgical approach would be to minimize surgical intervention and avoid unnecessary surgery while achieving a successful result.  Therefore, the majority of surgeons have favored a staged surgical protocol.  Since uvulopalatopharyngoplasty or uvulopalatal flap and genioglossus/hyoid advancement are all rather limited procedures without significant surgical morbidity, these procedures are usually first attempted to improve obstructive sleep apnea.  After a healing period of four to six months, a post-operative polysomnogram is obtained to evaluate outcome.  In patients with persistent obstructive sleep apnea, maxillomandibular advancement can then be performed.  Uvulopalatopharyngoplast/uvulopalatal flap in combination with genioglussus/hyoid advancement is usually considered as phase I operation, in which these procedures are often performed as a single operation.  Maxillomandibular advancement is considered as phase II operation.

However, the staged approach may actually increase unnecessary surgical manipulation for some patients.  Patients with factors that can negatively influence the outcome may have a low chance of success with phase I operation (Table 1).  Therefore, patients with severe obstructive sleep apnea, morbid obesity or significant hypopharyngeal obstruction such as severe mandibular deficiency, or patients who wish to have the best chance for a cure with a single operation can certainly be considered as candidates for maxillomandibular advancement as a primary surgical treatment option.  Clearly, it is important to review all possible treatment options and explain the rationale for sleep apnea surgery.  In the author’s opinion, combining all of the procedures in a single operation should be cautioned due to the potential for unnecessary surgery, as well as increased surgical morbidity and post-operative airway compromise. 

CONCLUSION

Successful surgical outcome depends on proper patient selection as well as the choice of surgical procedure(s).  The adaptation of a logical and systematic approach to clinical evaluation, treatment planning and surgical execution is necessary in order to maximize safety and improve surgical results.  New surgical techniques and evolving technology may potentially offer less invasive treatment modalities with broader patient acceptance and improvement in results.

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TABLES:

Table 1:  Factors influencing sleep apnea surgery outcomes

	Favorable	Unfavorable
Age	Younger patients (< 60 y.o.)	Older patients (> 60 y.o.)
Body habitus	Non-obese	Obese
OSA severity	Mild to moderate (RDI < 30)	Severe (RDI > 30)
Site of obstruction	Oropharyngeal (with tonsils)	Hypopharyngeal

 

Table 2: Defining surgical success

1. Improvement in quality of life with reduction of sleep apnea symptoms
2. Achieving RDI to less than 20 and reducing RDI by greater than 50%
3. Improvement of oxygen nadir to 90% with few desaturations to below 90%