Continuous positive airway pressure is usually prescribed as first-line treatment in preventing the upper airway collapse in patients with obstructive sleep apnea syndrome (OSAS), but long-term treatment adherence represents an evident problem. Among the variety of surgical procedures described to expand the pharyngeal lumen, uvulopalatopharyngoplasty (UPPP) remains the most frequently performed technique for the treatment of retropalatal obstruction.
Uvulopalatopharyngoplasty was first described by Fujita in 1981, and basically consists of a tonsillectomy, trimming of the soft palate and uvula, and suturing of the tonsillar pillars. Due to its low success rate and the considerable morbidities involved, the role of this technique has been questioned since the 1990s, and in the last two decades many modifications of UPPP have been proposed. The recent evolution regarding the techniques of pharyngoplasty has been focused on the concept of obtaining the expansion and stabilization of the pharyngeal airspace through the treatment of lateral pharyngeal wall (LPW) collapse rather than through ablation of the redundant pharyngeal soft tissue. The role of LPW in the pathogenesis of OSAS has been demonstrated by Schwab. The narrowing of the LPW appears to be the sole independent risk factor for OSAS.
The aim of this article is to present a new surgical technique, functional expansion pharyngoplasty (FEP), which represents a conservative modification of expansion sphincter pharyngoplasty (ESP), as described by Pang and Woodson. Applying the original technique, which includes a superolateral incision of the soft palatal mucosa to expose the anterior arching fibers of the palatoglossus muscle bilaterally, and the preparation of a dorsal palatal flap, we experienced dehiscence of the rotated palatopharyngeus muscle and troubles related to palate incisions, such as globus sensation and dry throat.
The FEP technique involves splinting of the LPW and advancement of the soft palate. This is obtained by means of the supero-lateral repositioning of the palatopharyngeus muscle, with a less aggressive and more “physiologic” approach to the LPW and soft palate, in order to both increase pharyngeal airspace and decrease pharyngeal collapse without undermining velum muscles, and in doing so avoiding scarring of the velum.
MATERIALS AND METHODS
We use this surgical technique for the treatment of retropalatal obstruction in OSAS patients as an isolated technique, or in combination with other nasal and hypopharyngeal techniques in a multilevel protocol. In our protocol, the surgery originates from a diagnostic workup completed by video sleep endoscopy. In the event of retropalatal obstruction and lateral pharyngeal wall collapse, we carry out this procedure in order to treat the retropalatal segment. In the event of the coexistence of retrolingual hypopharyngeal obstruction, the technique of hyoid suspension is carried out without sectioning the subhyoid muscles.
This surgery is performed while the patient is under general anesthesia with orally endotracheal intubation. The patient is placed in a supine position with the head extended, and a mouth gag is then used to adequately expose the oropharynx. The first step is a bilateral tonsillectomy, sparing the palatopharyngeus muscle (PPM) and the mucosa of the tonsillar pillars (Fig. 1). The key point of the surgical procedure is the identification and careful dissection of the PPM in the midpoint of the tonsillar fossa (Fig. 2). Using a dissection forceps and pulling up the muscular fasciculus with a 2.0 Vicryl, the authors (G.S., O.P.) separated the superior 2/3s of the PPM from the superior pharyngeus constrictor (SPC) muscle. Medially, a muscular rim of the PPM is preserved to avoid damage to the pillar mucosa and consequent retracting scar tissue. Using an angulate scissor (Long Fomon type), the PPM is transected, creating a superior flap medially based on the palatine musculature. The inferior third of the PPM is laterally sutured to the SPC (Fig. 3). With a gentle blunt dissection using curved haemostatic forceps, a tunnel is then obtained through the palatal musculature from the apex of the tonsillar fossa to the hamulus of the pterygoid process (Fig. 4). The PPM flap is then elevated with a superolateral rotation through the palatine tunnel and fixed to the palatine musculature, close to the pterygoid hamulus, using a 2-0 MH Vicryl “figure-eight suture” (Figs. 5a–b). The PPM flap is anchored, stitched three times (with different angulations) into the muscle before its relocation in order to obtain a steady anterolateral fixation of the flap, which moves the soft palate in a forward direction and creates an immediate widening of the antero-posterior and lateral oropharyngeal diameters (Fig. 6). The procedure concludes with the suturing of the superior 2/3s of the tonsillar pillars. The uvula is trimmed only when abnormally elongated (Fig. 7).
A total of 85 patients with a mean age of 42.7 years underwent FEP over a 3-year period. The mean preoperative AHI was 33.3/h, while the mean time of SaO2 < 90% was 11.2%. Considering the classic definition of successful surgical treatment of OSAS (decrease in AHI higher than 50% of the preoperative values and final AHI lower than 20%), the success rate was 89.2%. Both AHI and mean time of SaO2 < 90% were significantly decreased from preoperative levels at 6 month follow-up (AHI = 11.7/h and mean time of SaO2 < 90% = 4.6%). No dysphagia or swallowing disturbances were referred. Only two cases of bleeding from tonsillar fossa were observed.
Approximately 30 years have passed since the introduction of UPPP. It is time to establish that this technique no longer represents the ideal technique for treating retropalatal pharyngeal obstruction in OSAS patients. Several studies have demonstrated that a common cause of UPPP failure is persistent retropalatal obstruction, and in some patients a worsening of the OSAS is observed. The cause of this phenomenon is represented by a defect of the technique itself; it generates a vast bloody area that simultaneously interests the entire velopharyngeal isthmus, and in many cases the excessive postsurgical scar retraction leads to a narrowing of the retropalatal airway lumen in the midline. In addition, studies carried out with magnetic resonance imaging (MRI), as well as the results obtained by sleep endoscopy, have modified the idea of pharyngeal physiopathology in OSAS patients, pointing out the crucial role of lateral wall collapse in the genesis of pharyngeal obstruction rather than the anteroposterior collapse of the soft palate.
The first surgical technique aimed at stabilizing the lateral wall was lateral pharyngoplasty, described by Cahali in 2003, a technique that was not widely used. In fact, this procedure involves a notable modification of the lateral wall with sectioning of the superior pharyngeal constrictor (SPC) muscle and the risk of important complications, including postoperative dysphagia. Instead, the surgical technique ESP, described by Pang and Woodson in 2007, has had much greater acceptance. It originated from the technique of sphincter pharyngoplasty, described for the correction of palatal incompetence using medial rotation of the palatal pharyngeal muscle, in such as way as to narrow the velopharyngeal isthmus. In the case of OSAS patients, the muscle is instead superolaterally rotated and sutured to the palatine musculature after incision of the muco-palatal plane. The surgery concludes with resection of the uvula.
The aim of the FEP technique that we propose is to put tension on the lateral wall, allowing advancement of the soft palate more efficaciously and less invasively than the previous techniques of lateral pharyngoplasty. The first assumption of physiopathological order is that a widening and stabilization of the pharyngeal airway lumen can be obtained by ablation of the redundant tissue only when it is found in those few patients with markedly hypertrophic tonsils (Friedman stages II and III). In all other cases, the obstructive problem is mostly linked to functional problems, in particular to increased collapsibility of the lateral pharyngeal wall. A physiological correction of this phenomenon can be obtained by taking advantage of the anatomical characteristics of the palatal pharyngeal muscle. It is comprised of a vertical component, which originates from the palatine aponeurosis, encompasses the levator veli palatini in its palatal course and then descends up to the thyroid cartilage of the larynx, making a posterior palatine arch and a horizontal component, which also originates from the palatine aponeurosis and is positioned in continuity between the palate and the superior constrictor pharyngeal muscle. For this reason, the isolation of the vertical component of the muscle and its repositioning as superolateral is possible by means of a tunnel that ideally reaches the pterygoid process, and therefore the pterygomaxillary raphe. This constitutes a physiological method for obtaining the widening of the retropalatal airway lumen, advancing the soft palate, and putting tension on the lateral pharyngeal wall. The lines of scar tension that develop in the superolateral sense lead to a stable widening of the pharyngeal diameters.
Our technique does not involve sensitivity and swallowing disturbances. In fact, the complete preservation of the soft palate and uvula involves less invasivity than the ESP technique. In this respect, it is worth noting that the muscle spindles of the palatoglossus muscles (anterior part of the soft palate) play a role in inducing unconstrained swallowing. Therefore, this anterior palatine arch, together with the paired muscularis uvulae, must be protected when performing soft palate surgery. On the other hand, the palatopharyngeal muscle (posterior part of the soft palate) has no muscle spindles; therefore, it can be partially separated without impeding swallowing, or without the future possibility of nasally applied, continuous positive airway-pressure therapy.
As presented here, functional expansion pharyngoplasty appears to be an effective pharyngoplasty technique. When compared to expansion sphincter pharyngoplasty, it appears to be a more physiologic and less invasive surgical technique, providing less discomfort and quicker healing. This technique can be utilized with success in patients with documented retropalatal obstruction due to the lateral pharyngeal walls collapse, which is typical in OSAS patients (best-assessed in an endoscopic examination) and obtains positive results with minimum collateral effects, even in case of small tonsils size.
The authors would like to thank Professor Eric J. Kezirian (Department of Otolaryngology, University College of San Francisco) for his editorial support. The authors also would like to express their gratitude to Dr. Valentina Pinto (Department of Plastic surgery, Bologna University Hospital) for her contributions to the figures.