Exploring GBAT as an OSAS Treatment Option

Genioglossus advancement (GGA) is one of several options that exist for treatment of obstructive sleep apnea syndrome (OSAS). GGA can be used for isolated tongue base obstruction or can be an adjunct to other sleep procedures when mixed patterns of obstruction occur. Many patients seek relief of OSAS symptoms, wish to avoid the cardiopulmonary sequelae of OSA, and also have poor CPAP tolerance. Facing these struggles, a 40-year-old, African-American woman found relief through GGA using the Genial Bone Advancement Trephine™ (GBAT™) System.

BACKGROUND

OSAS is a well-described condition caused by collapse of upper airway structures during sleep. The negative effects of OSAS on quality of life and general health have been well documented. Despite the availability of multiple treatment options, management of OSAS remains a challenge. The most successful first-line treatment is CPAP. However, CPAP is not uniformly accepted by all patients. Long-term adherence rates have, however, been variable, ranging from 50% to 85%.¹ Not surprisingly, some patients pursue surgical therapy as an alternative to CPAP use.

Surgery remains a second-line option for treatment of OSAS due to many factors including difficult postoperative recovery, comorbid conditions that may make patients poor surgical candidates, complications associated with the therapy, and treatment failures. When surgical treatment is contemplated, the first, and perhaps most important, task is to define the pattern of obstruction in each individual patient. Areas that are frequently identified include the nasal cavity, soft palate, posterior pharynx, and base of tongue. Less commonly implicated areas include the supraglottic structures and trachea. Collapse at the level of the soft palate and oropharynx is classified as retropalatal whereas that of the hypopharynx up to and including the base of the tongue is referred to as hypopharyngeal. Often, mixed patterns are present with both a retropalatal and hypopharyngeal component. Research of uvulopalatopharyngoplasty (UPPP) highlights how a patient’s particular pattern of collapse is important. Friedman et al in 2004 reported that success with UPPP alone could be as low as 8% if the tongue base was implicated as a component of obstruction.² Conversely, success rates upwards of 80% were seen when the tongue base was uninvolved. As a consequence, the author proposed a staging system to identify the site of obstruction and to dictate appropriate surgical therapy.² The need for site-specific surgery has given rise to many new techniques tailored to the various areas of pathology. Each procedure has its own technical considerations and varying degrees of success.

Specifically looking at surgical correction of hypopharyngeal obstruction has been the focus of much investigation, and many techniques targeting this area have been described. Irrespective of the procedure, the aim of hypopharyngeal surgery is to increase the size of the posterior pharyngeal space, thereby decreasing the likelihood of collapse. Currently, one of the most common procedures to attain this goal is GGA. In 2006, Kezirian et al performed an evidence-based review of hypopharyngeal surgery.³ The authors identified 91 reported cases of genioglossus advancement in the literature, of which 56 were successful (success defined as greater than 50% reduction in AHI, and an overall AHI of less than 20). The 62% success rate of genioglossus advancement in decreasing the AHI placed it ahead of mortised genioplasty, radiofrequency tongue base ablation, midline glossectomy, hyoid suspension, and tongue stabilization.

The GBAT System developed by Stryker Leibinger is the latest development in genioglossus advancement. The system was designed for one-step isolation and advancement of the genioglossus muscle. In this procedure, a gingivobuccal incision is created to skeletonize the anterior face of the mandible. Subsequently, a circular osteotomy, performed with a 12 or 14 mm trephine over a guide plate, captures the attachment of the genioglossus muscle on the genial tubercle. The bone segment and attached musculature are pulled forward and the outer cortex and medullary bone are removed. The remaining inner cortex with attached musculature is fixed to the anterior surface of the mandible with a prebent plate. The subsequent advancement of the tongue musculature opens the posterior airway.

PATIENT CASE

Our case patient was a 40-year-old, 5-foot, 4-inch-tall, 160-pound (BMI=27.5) African-American woman with a long history of loud snoring as well as frequent apneic episodes witnessed by her bed partner. She reported a 1-year history of restlessness, lethargy, excessive daytime sleepiness, and occasional morning headaches. Due to concern over the witnessed apnea, she was urged to pursue additional evaluation.

The patient was initially evaluated by nocturnal polysomnography at the Jefferson Sleep Disorders Center. On evaluation, she was observed to snore loudly throughout the night. Her AHI was 23.08, and her SaO2 nadir was measured at 90%. The results were interpreted as consistent with moderate OSAS, and CPAP was recommended. Despite multiple attempts to utilize the device, the patient could not tolerate CPAP due to mask discomfort. She was, therefore, referred for surgical consideration.

Her initial evaluation revealed a Friedman tongue position of III with a short palate and tonsil size of I.² Mueller’s maneuver identified collapse at the level of the base of tongue. Her Epworth Sleepiness Scale (ESS) was 11. She had no history of prior upper airway surgery.

She subsequently underwent GGA with the GBAT System under general anesthesia without any adjunctive procedures. Follow-up assessment 2 months later revealed persistent but improved snoring with subjectively improved sleep and decreased daytime somnolence. Her Epworth Sleepiness Scale decreased from 11 to 7. Follow-up nocturnal polysomnography, revealed an AHI that had dropped from 23.08 to 4.7. Her overnight SaO2 nadir remained stable at 91%.

DISCUSSION

Historically, the execution of GGA has not been without complications. Incomplete capture of the genioglossus, damage to the teeth while performing the osteotomy, and avulsion of the genioglossus muscle off the bone have all been described in the literature. In our experience, the GBAT system minimizes many of these morbidities associated with GGA. The first advantage is the shape of the osteotomy. In 1995, Mintz et al demonstrated that a circular osteotomy of 12 mm adequately captured the genioglossus at its attachment.^4,5 They further demonstrated that damage to the tooth roots could be avoided by preoperative assessment with panoramic radiographs. In 2005, Hennessee et al demonstrated, on seven cadaveric heads, the GBAT System’s ability to capture 100% of the genial tubercles and 85% of its muscular attachments by circular osteotomy, all with no damage to the tooth roots.⁶ The self-contained trephine allowed for quick and safe performance of the osteotomy and thereby decreased the likelihood of damage to the surrounding structures and avulsion of the musculature off the bone segment. Additionally, in the largest series to date, the GBAT System was used in 35 patients with limited complications that included transient chin numbness, tooth numbness, hematoma formation, and plate exposure.⁷

Using a >50% reduction in the AHI and an AHI of <20 as a measure of success in the surgical treatment of OSAS, the GBAT System adequately treated the case patient’s sleep-disordered breathing. At our institution, Thomas Jefferson University, the GBAT system is frequently employed because it is an effective means of advancing the tongue base and is a technically easy treatment option for OSAS, which can be employed as an adjunctive procedure or in isolation. The case study illustrates both the benefit and the minimal morbidity of this procedure in one patient.

Scott Troob is a third-year medical student at Jefferson Medical College, Philadelphia, interested in pursuing a career in otolaryngology. Karl Doghramji, MD, is professor of psychiatry, Jefferson Medical College; medical director, Jefferson Sleep Disorders Center; and program director, Fellowship in Sleep Medicine, Thomas Jefferson University. Maurits Boon, MD, is a clinical instructor at Jefferson Medical College and associate residency director at Thomas Jefferson University with special interest in treating and researching obstructive sleep apnea.

REFERENCES

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