of the Literature REVIEW

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1 REVIEW Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring: a Review of the Literature Boris A. Stuck, MD; Joachim T. Maurer, MD; Gerhard Hein, MD; Karl Hörmann, MD; Thomas Verse, MD Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Mannheim, Mannheim, Germany Study Objectives: Radiofrequency surgery of the soft palate presents a promising alternative for the treatment of snoring. The aim of this study was to give an overview of the current literature and to quantify the results in terms of a meta-analysis of treatment efficacy. Methods: Current databases were searched for publications concerning the treatment of snoring with radiofrequency surgery up to January Only original articles published in peer-reviewed journals were taken into consideration. Results: The review is based on 22 publications, mostly consisting of prospective noncontrolled clinical trials. Snoring was assessed with the help of visual analogue scales or snoring scores provided by the bed partner. In all these trials, a significant reduction of snoring was reported. Postoperative morbidity was low, but complication rates differed substantially. INTRODUCTION IN CONTRAST TO OBSTRUCTIVE SLEEP APNEA, WHERE NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE IS STILL THE GOLD STANDARD OF TREATMENT, PRIMARY OR HABIT- UAL SNORING IS USUALLY ADDRESSED WITH THE HELP OF INTRAORAL DEVICES OR SURGERY. Following the inauguration of the laser-assisted uvulopalatoplasty (LAUP) by Kamami et al in 1994, 1 various surgical techniques have been developed. Although LAUP and uvulopalatopharyngoplasty (UPPP) are the most widespread procedures, they are associated with significant postoperative morbidity and, especially in the case of UPPP, are usually performed under general anesthesia. Therefore, much effort has been invested in establishing minimally invasive techniques for the treatment of snoring. In 1998, Powell et al first reported the use of radiofrequency surgery of the human soft palate in the treatment of snoring. 2 Promising results were presented for treatment efficacy as well as intraoperative and postoperative morbidity. In the following 5 years, various study groups attempted to repeat or modify this study in order to assess the value of the new procedure. In the meantime, a large number of studies have been performed using various types of radiofrequency devices. The aim of the present study was to provide an overview of the current literature concerning radiofrequency surgery of the soft palate in the treatment of snoring and to quantify the effect of the different treatment methods. Disclosure Statement Karl Hörmann, MD, has a consultancy agreement with Gyrus ENT. Submitted for publication July 2003 Accepted for publication December 2003 Address correspondence to: Boris A. Stuck, MD, Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Mannheim, Mannheim, Germany; Tel: ; Fax: ; boris.stuck@hno.ma.uni-heidelberg.de Conclusions: According to all of the published material, radiofrequency surgery of the soft palate leads to a significant reduction of subjective snoring, and snoring is reduced to a tolerable level. Nevertheless, these findings will have to be confirmed by controlled clinical trials. Key Words: radiofrequency surgery, soft palate, snoring Abbreviations: BMI, body mass index; LAUP, laser-assisted uvulopalatoplasty; RDI, respiratory disturbance index; UPPP, uvulopalatopharyngoplasty Citation: Stuck BA; Maurer JT; Hein G et al. Radiofrequency surgery of the soft palate in the treatment of snoring: a review of the literature. SLEEP 2004;27(3): METHODS Our systematic review of the current literature was based on articles published in peer-reviewed journals up to January Only original articles were considered. Articles were included in the review if they referred to the treatment of the human soft palate with any device delivering radiofrequency energy in patients complaining of snoring. Publications concerning the treatment of obstructive sleep apnea as the primary focus were not included. MEDLINE, as provided by the National Library of Medicine ( was used for the literature survey, searching for combinations of the terms sleep, radiofrequency, soft palate, and snoring. Additionally, these articles were reviewed for further citations in their reference lists; files from personal communications and databases were also included. The selected articles were screened for the following information: study design (prospective / retrospective clinical trial, controlled, randomized); number of patients enrolled; inclusion criteria concerning body mass index (BMI) and severity of sleep-disordered breathing in terms of respiratory disturbance index (RDI), device, and treatment protocol used; follow-up periods; criteria for success; postoperative complications; and overall outcome. In order to compare the different data for postoperative complications, a complication rate was based either on the number of treatment sessions as given in these publications or, if no complication rate was provided, as calculated from the raw data. Mucosal erosions or ulcerations or prolonged dysphagia were classified as minor complications; palatal fistula or uvula loss were classified as moderate. The need for hospital admission or life-threatening events was classified as severe complications. The results concerning the overall outcome of temperature-controlled radiofrequency tissue ablation were summarized in terms of a meta-analysis for prospective trials that provided quantitative data on subjective improvement. One analysis was done for studies using 10-cm visual analogue scales (7 studies) and 1 was performed for studies based on 10- digit snoring scales (4 studies). In addition to summarizing the results in tables (mean ± SD before and after treatment, mean treatment effect ± SD), the weighted average means and SD were calculated using SAS (SAS Institute Inc, Cary, NC, USA). The weights were based on the sample size of the studies. To improve the analysis by including missing data (means or SDs) SLEEP, Vol. 27, No. 3, Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring Stuck et al

2 and in order to obtain the raw data (pretherapeutic and posttherapeutic snoring scores) to perform a genuine meta-analysis, all primary authors of the studies mentioned above were contacted. If not provided in the studies or by the authors, the SD of the studyspecific treatment effect was calculated based on the SDs of the scores before and after treatment (SD treatment effect = (SD before2 + SD after2 )). The covariance was set to 0 as a conservative assumption. An overall P value was calculated for the studies using the snoring index and visual analog scales. With regard to the information given by the authors, a t test was assumed in order to calculate the overall P value. The null hypothesis is no effectiveness: mean of scores before minus mean of scores after equals 0 versus the alternative effectiveness: mean of scores before minus mean of scores after does not equal 0. The underlying test statistic can be described by the following term: If the null hypothesis is correct, this test statistic follows a t distribution. Hence, the null hypothesis is rejected if the absolute value of this term exceeds the corresponding value of the t distribution. The P value denotes the probability that the sample generates a test statistic that leads to a rejection of the null hypothesis. In case of a 2- sided test, it is calculated according to the formula: P value = 2*(1 P (t emp)). P is the value of the respective cumulative distribution function of the underlying test distribution based on the mean scores and SD before and after treatment. RESULTS The survey of the literature generated 22 original articles dealing with radiofrequency surgery of the soft palate in the treatment of snoring Eighteen studies were prospective clinical trials; 15 of these focused on treatment efficacy, 3 of which included a comparison with other treatment modalities such as intraoral devices, LAUP, or UPPP. Two studies restricted themselves to assessing postoperative complications, and 1 study was a medium-term follow-up study of previously published material. Four studies were retrospective trials (2 addressing treatment efficacy and 2 referring to postoperative complications only). To date, no controlled clinical trial with an untreated control group exists, neither in nonrandomized or randomized form. Nineteen of the 22 studies used temperature-controlled radiofrequency tissue ablation (Somnoplasty), a monopolar delivery system with built-in temperature sensors. The remaining 3 studies used the Ellman (monopolar), 10 VidaMed, 12 or Coblation (bipolar) 17 system. Between 1 and 4 application sites per treatment session were selected. Obstructive sleep apnea was ruled out with polysomnography in 19 of these studies, with a maximum respiratory disturbance index of 10 or 15. Furthermore, obese patients were excluded in most of the trials (16 out of 22), although the maximum body mass index varied between studies (between 27 and 40 kg/m 2 ). Follow-up periods were usually 6 to 8 weeks, but especially retrospective trials had a significantly longer follow-up time (2-18 months). 20,22,23 Concerning postoperative complications, no serious adverse events were reported, though it should be mentioned that there was a significant variation in the overall complication rates provided, which ranged from Table 1 Energy Delivery and Number and Nature of Postoperative Complications in Studies that Used Radiofrequency Surgery of the Soft Palate to Treat Snoring Study Device Study Subjects, Lesions, Energy / Energy in Minor Moderate Comments / Specifications for Complications / Design no. no. Session, J Total Events Events Adverse Events Powell Somnus PNRCT % 0% Mucosal erosion (11) Boudewyns Somnus PNRCT % 2% Mucosal erosion (19), swelling (1), bleeding (2), fistula (1), uvula loss (1) Cartwright Somnus PNRCT 10 No data No data No data No data No data No data Coleman Somnus PNRCT % 0% Mucosal erosion (6) Emery Somnus PNRCT 43 44% 3% Mucosal injury (47), palatal fistula (1), uvula loss (1), uvula sloughing (1) No data for subgroup provided No data for subgroup provided Fischer Somnus PNRCT 4 No data No data No data No data No data No data Hukins Somnus PNRCT % 0% Mucosal erosion (3) Li Somnus PNRCT 8 No data % 0% Retreatment of 8 patients with relapse, initial study: Powell Taliaferro Ellman PNRCT % 0% Mucosal injuries (8) Troell Somnus PNRCT % 0% Mucusal erosion (11) Back VidaMed PNRCT % 0% Ferguson Somnus PNRCT % 0% 1 lesion / treatment % 0% 3-4 lesions / treatment Sher Somnus PNRCT 105 No data % 2% Mucosal ulceration (3), palatal fistula (2), uvula sloughing (2) No data for subgroups provided No data for subgroups provided Terris Somnus PNRCT % 0% Mucosal erosion (23), 37% of those occult Pazos Somnus Retro 30 No data No data No data 0% 50% Mucosal breakdown (11), uvula sloughing (2) Back Coblation PNRCT % 0% Mucosal infection ( small abscess ) (4) Blumen Somnus PNRCT % 0% Haraldsson Somnus PNRCT * 0% Mucosal ulceration (2), hyperreflexia (2), otalgia (2) Johnson Somnus Retro 60 No data % 0% Prolonged pain (6), postoperative bleeding (1) Terris Somnus PNRCT No data Trotter Somnus Retro No data No data Stuck Somnus Retro 85 No data No data No data 1% 0% Mucosal erosion (1) Complication rate according to the number of treatment sessions; PNCRT refers to prospective nonrandomized clinical trial; Retro, retrospective trial; No. of lesion, number of lesions per treatment session (temperature-controlled radiofrequency surgery only, mean values); Energy / Session, amount of energy applied per treatment session (temperature-controlled radiofrequency surgery only, mean values); Energy in total: total amount of energy applied per patient (temperature-controlled radiofrequency surgery only, mean values); RF, radiofrequency. *Total number of treatment sessions unknown SLEEP, Vol. 27, No. 3, Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring Stuck et al

3 0% 12,13,18,20 to 50%. 16 The most frequently reported complication was a mucosal erosion or ulceration. Mucosal blanching was also reported to accompany the treatment and to be related to the intensity of postoperative pain 12 but was not assessed by us as a complication. In general, the comparison between different studies concerning postoperative complications poses difficulties. Especially mucosal erosion seems to a certain extent inevitable at the site of the intrusion of the needle (and is not regarded as a complication). It has to be distinguished from secondary erosions or ulcerations due to the energy delivered. Nevertheless, mucosal erosion is often listed as a complication without further description. Four studies reported moderate complications in terms of severe palatal damage (palatal fistula, uvula loss, or sloughing). 3,6,14,16 One of these studies reported the highest rate of overall postoperative complications (50%), all being moderate complications such as major mucosal breakdown and uvula sloughing. 16 In this study, technical parameters and the intraoperative setting were comparable to the other studies using FIGURE 1 Mean treatment effect and SD of prospective studies with the Somnus system. VAS refers to visual analog scales; SI, snoring index. *Weighted means and SDs. Table 2 Summary of Results of Prospective Trials with the Somnus System* Study Subjects, Measurement Preoperative Postoperative Treatment P values no. Scores Scores Effect Powell VAS 8.3 ± ± ± 1.7 <.0001 Coleman VAS 8.3 ± ± ± 2.5 <.0001 Hukins VAS 7.5 ± ± ± 2.8 <.001 Ferguson single lesion 16 VAS 8.9 ± ± ± 2.3 <.01 Ferguson multiple lesions 31 VAS 9.1 ± ± ± 2.8 <.01 Sher VAS 7.8 ± ± ± 3.0 <.0001 Blumen VAS 8.3 ± ± ± 1.3 <.01 Terris VAS 7.5 ± ± ± 3.3 <.001 All studies using VAS 231 VAS 8.1 ± ± ± 2.7 <.0001 Boudewyns SI 7.6 ± ± ± 2.7 <.001 Cartwright SI 7.5 ± ± ± 3.3 <.001 Emery single lesion 19 SI 7.8 ± ± ± 2.8 <.05 Emery multiple lesions 24 SI 8.9 ± ± ± 1.9 <.05 Haraldsson SI 8.2 ± ± ± 3.2 <.01 All studies using SI 114 SI 8.0 ± ± ± 2.7 <.0001 *Data are presented as weighted means ± SD weights based on sample size SD calculated based on the weighted SD before and after treatment VAS refers to visual analogue scale; SI, snoring index temperature-controlled radiofrequency surgery. One significant difference was the regular use of oral corticosteroids before and after treatment in every patient. Series with a larger number of patients showed complication rates of about 1% to 5%. 3,14,23 In those studies where postoperative morbidity was compared with other surgical approaches (UPPP or LAUP), radiofrequency surgery was associated with the least amount of postoperative pain. 4,11,18 For example, mean postoperative pain duration was 2.6 days for radiofrequency surgery compared to 13.8 days for LAUP and 14.3 days for UPPP in the study of Troell et al. 11 Concerning the amount of energy delivered with temperature-controlled radiofrequency tissue ablation, comparable protocols were used for single-lesion treatments. Six hundred forty-seven 14 to J per treatment session were applied in these cases. If 3 or more lesions were created per session, the mean amount of energy delivered varied between and J. Due to the lack of data in these studies, comparisons concerning the rate of postoperative complications could not be made. Apart from 2 early studies that used 80 C as the target temperature, 2,11 85 C was selected in all the other trials using the Somnus system. The number and specifications of postoperative complications and the amount of energy delivered per treatment session are shown in Table 1. Treatment efficacy was assessed with the help of visual analogue scales or snoring scores filled out by the bed partner in 16 of the 18 studies addressing treatment efficacy. Objective assessment of snoring sounds was only performed in 3 studies and did not correlate with subjective evaluations. 4,8,15 As stated above, the prospective studies using temperature-controlled radiofrequency tissue ablation and providing results of subjective snoring (visual analogue scales or snoring index) were summarized in terms of 2 meta-analyses. In those studies using the visual analogue scales, a total number of 231 patients were treated. The weighted mean score ± SD of these studies was reduced from 8.1 ± 1.8 to 3.5 ± 2.2. The mean weighted treatment effect was 4.8 ± 2.8. In those studies using the snoring index, a total number of 114 patients were treated. The weighted mean ± SD was reduced from 8.0 ± 2.1 to 3.4 ± 2.3, and the weighted mean treatment effect was 4.7 ± 3.1. The statistical evaluation concerning the overall P values of the studies that used visual analog scales and the snoring index provided a P value of <.0001 for both study groups. All primary authors of the above mentioned studies could be contacted and have responded. Missing data (eg, SDs) could be provided in every case. Only 4 out of 11 primary authors were able or willing to provide us with the raw data of their studies 2,8,18,19 ; an analysis of the raw data therefore could not be performed. Detailed results of the statistical analysis are given in Table 2. The study-specific treatment effects and SDs are shown in Figure 1. In 3 trials, different treatment protocols concerning the number of applications sites per treatment session were compared (ie, 3-4 versus 1). 6,13,14 One study was based on snoring scores 6 and compared a group of 19 patients receiving 698 J (mean value) at the midline as a single treatment to a group of 24 patients receiving 3 lesions with a mean total number of 1254 J per treatment session. The group receiving multiple lesions (total amount of energy per patient, 2196 J) showed a slightly more pronounced reduction of mean snoring scores (8.9 to 2.5) compared to the group receiving single lesions (total amount of energy per patient, 2165 J; 7.8 to 2.3). The 2 studies comparing the effects of sin- SLEEP, Vol. 27, No. 3, Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring Stuck et al

4 gle- versus multiple-lesion treatments based on visual analogue scales showed comparable effects for these 2 treatment protocols, 13,14 with a higher total amount of energy delivered per patient for the multiplelesion group (1676 vs 3418 J, 13 and 1898 vs 2001 J 14 ). The main advantage of multiple-lesion treatments seems to be the reduced number of treatment sessions necessary (3.3 vs 1.75, vs 1.94, 13 and 2.9 versus ) rather than a higher efficacy concerning the final outcome. In a study with a longer follow-up period, a relapse over time was seen in 41% of the patients. 9 The results for the visual analog scales in this study increased from 2.1 to 5.7 after 14 months. Eight of the 9 patients showing a significant relapse were again treated with radiofrequency surgery. Their mean snoring score could again be reduced from 5.8 to 3.3. Two studies reevaluated initial success rates (3 months) after 12 or 9.5 months, respectively. 12,17 Mean postoperative snoring index increased from 4 to 5 in the first study (12 months), 12 and the success rate decreased from 33% to 28 % in the second (9.5 months). 17 Detailed information focusing on overall outcome is given in Table 3. DISCUSSION Since the first report in 1998, a total amount of 22 studies concerning the treatment of the human soft palate with radiofrequency surgery for snoring have been published. Postoperative morbidity was low in these trials, especially when compared to standard procedures (LAUP, UPPP). Although complication rates differ substantially, no serious adverse events have been reported to date. The disproportionately high complication rate of 50% in 1 of the studies may be due to the specific protocol employing the regular use of corticosteroids before and after treatment; in the other studies, corticosteroids were usually only given in selected cases with severe postoperative swelling. Presumably, a learning curve exists for this procedure, and it may be assumed that complications decrease over time with increasing experience of the surgeon, as it has been shown for tongue-base reduction with Table 3 Treatment Outcome of Studies that Used Radiofrequency Surgery of the Soft Palate to Treat Snoring radiofrequency surgery. 23 Adequate data for soft-palate radiofrequency surgery were not provided in the publications found. The vast majority of the publications (19 of 22) used temperature-controlled radiofrequency tissue ablation (Somnoplasty). This monopolar system provides built-in temperature control so that the maximum temperature can be maintained during the entire procedure. Furthermore, the thermic effects of this technique are self limited due to regimentation of target temperature; maximum effects are achieved after a specific time. 24 This technique is therefore often considered to be particularly safe. Due to the limited number of studies with different delivery systems, a satisfactory comparison of treatment effects or complication rates is difficult to establish. Therefore, it remains unclear whether these additional technical features (and additional costs) are of clinical benefit. Although all published material reported beneficial effects on snoring, the evidence for the beneficial effects of radiofrequency surgery is limited by the lack of controlled clinical trials and the lack of objective assessment criteria in respect to snoring. The lack of reliable tools for the objective assessment of snoring sounds may explain the prevalent use of subjective treatment evaluation. Significant placebo effects have to be considered when evaluating treatments for snoring. According to the current literature, snoring can be significantly reduced to a nonbothersome level with the repeated administration of radiofrequency energy to the soft palate. Presenting a summary of the data available, results are given in terms of a meta-analysis for prospective clinical trials using the Somnus system. Analyses were performed for 2 studies based on visual analogue scales and 2 based on the snoring index. In those studies, the weighted mean scores were reduced from 8.1 ± 1.8 to 3.5 ± 2.2 (visual analogue scale) or from 8.0 ± 2.1 to 3.4 ± 2.3 (snoring index). Overall P values for the studies using the visual analogue scale and snoring index were <.0001 in both study groups. However, it should be kept in mind that such results are mostly evoked by the increase in sample size when adding 1 study to another. A numerical effect does not necessarily mean that the effect also exits contents wise. However, the summary of descriptive statistics combined with the P Study Treatment Study Subjects, Mean Mean Measurement Follow-Up Results Snoring Comments Device Design No. RDI BMI Period Powell Somnus PNRCT VAS 8-12 weeks First study Boudewyns Somnus PNRCT SI 8 weeks Cartwright Somnus PNRCT SI 8 weeks Compared to Retainer Coleman Somnus PNRCT VAS 8 weeks Emery Somnus PNRCT SI 7 weeks lesion / treatment SI 7 weeks lesions / treatment Fischer Somnus PNRCT Satisfaction 8 weeks 75% Satisfaction Small RF subgroup Hukins Somnus PNRCT VAS 8 weeks Li Somnus PNRCT 22 No data 27.4 VAS (Relapse) 14 months 41% Relapse Treatment repeated Taliaferro Ellman PNRCT Satisfaction 3-5 weeks 84% Satisfaction Troell Somnus PNRCT 22 No data 27.1 Postoperative pain No data No data Compared LAUP/UPPP Back VidaMed PNRCT 21 No data 26.9 SI 3 (12) months 9-4 (5) Ferguson Somnus PNRCT 16 No data 27.4 VAS 6 weeks lesion / treatment 31 No data 28.7 VAS 6 weeks lesions / treatment Sher Somnus PNRCT VAS 8 weeks Entire group 57/105 No data No data VAS 8 weeks lesion / treatment 32/105 No data No data VAS 8 weeks lesions / treatment Terris Somnus PNRCT Complications No data No data 37% occult lesions Pazos Somnus Retro 30* No data No data Complications 1 month No data Back Coblation PNRCT 18 No data 25.7 SI 3 (9.5) months 33% Success Blumen Somnus PNRCT VAS 6-8 weeks Compared to LAUP Haraldsson Somnus PNRCT 16 No data 26.2 SI No data Johnson Somnus Retro 60 No data No data VAS 2-18 months Terris Somnus PNRCT VAS 16 weeks Compared to LAUP Trotter Somnus Retro 36 No data No data VAS 17.5 months 9 7 General anesthesia Stuck Somnus Retro 85 No data No data Complications 4 months No data PNRCT refers to prospective nonrandomized clinical trial; Retro, retrospective reviewrf, radiofrequency; retro, retrospective trial; RDI, respiratory disturbance index; BMI, body mass index; VAS, visual analog scale (0-10); SI, snoring index (0-10); LAUP, laser-assisted uvulopalatoplasty; UPPP, uvulopalatopharyngoplasty *Soft palate plus tongue base patients, number of patients in soft palate subgroup unknown, Complications assessed with transnasal endoscopy Mean values Success defined as postoperative snoring index <3, median values SLEEP, Vol. 27, No. 3, Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring Stuck et al

5 values gives a concise and satisfactory pattern concerning the therapeutic effects. Nevertheless, the authors are aware of a possible publication bias. Three studies compared single-lesion with multiple-lesion protocols, showing comparable or only slightly higher success rates for multiplelesion protocols. The main advantage of multiple-lesion protocols seems to be the reduced number of treatment sessions. A relapse of snoring over time seems to be a problem for at least some of the patients, although additional treatments with the same technique may be beneficial in these cases. With regard to the fact that a relapse of snoring is a general problem in surgical treatment, the possibility of repeated treatment sessions in cases of snoring relapse has to be regarded as an advantage. According to the data available, radiofrequency surgery should be considered for the treatment of snoring if anatomic conditions are given that are generally considered suitable for radiofrequency surgery (small uvula, absence of relevant tonsilar hypertrophy, and a floppy soft palate). An important advantage of this technique lies in the minimally invasive nature of the procedure. Nevertheless, the necessity of repeated treatment sessions and the significant costs for the radiofrequency generators and needle devices should be kept in mind as a disadvantage of this technique. Randomized placebo-controlled clinical trials should be performed in the near future in order to strengthen the evidence for the use of radiofrequency surgery. Furthermore, the development and use of reusable and sterilizable treatment devices would be beneficial in reducing costs and ensuring reimbursement. CONCLUSION According to the current literature, radiofrequency surgery of the soft palate is a valuable tool in the management of snoring and is associated with the least amount of postoperative morbidity. Nevertheless, controlled clinical trials and objective outcome assessments are still lacking. REFERENCES 1. Kamami YV. Outpatient treatment of sleep apnea syndrome with CO2 laser: laser-assisted UPPP. J Otolaryngol : Powell NB, Riley RW, Troell RJ, Li K, Blumen MB, Guilleminault C. Radiofrequency volumetric tissue reduction of the palate in subjects with sleep-disordered breathing. Chest 1998;113: Boudewyns A, Van De Heyning P. Temperature-controlled radiofrequency tissue volumetric reduction of the soft palate (Somnoplasty ) in the treatment of habitual snoring: Results of a European multicenter trial. Acta Otolaryngol 2000;120: Cartwright R, Venkatesan TK, Caldarelli D, Diaz F. Treatments for snoring: A comparison of Somnoplasty and an oral appliance. 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Otolaryngol Head Neck Surg 2002;127: Trotter MI, D'Souza AR, Morgan DW. Medium-term outcome of palatal surgery for snoring using the SomnusTM unit. J Laryngol Otol 2002;116: Stuck BA, Starzak K, Verse T, Hörmann K, Maurer JT. Complications of temperaturecontrolled radiofrequency volumetric tissue reduction for sleep disordered breathing. Acta Otolaryngol 2003;123: Stuck BA, Kopke J, Maurer JT, et al. Lesion formation in radiofrequency surgery of the tongue base. Laryngoscope 2003;113: SLEEP, Vol. 27, No. 3, Radiofrequency Surgery of the Soft Palate in the Treatment of Snoring Stuck et al