An adjunctive method of radiofrequency volumetric tissue reduction of the tongue for OSAS

Abstract

OBJECTIVES: Temperature-controlled radiofrequency volumetric reduction (TCRF), a minimally invasive procedure, has been used to treat tongue base obstruction in Obstructive Sleep Apnea Syndrome (OSAS). An adjunctive method was objectively evaluated.

METHOD: A prospective, nonrandomized clinical study was undertaken on 20 consecutive OSAS patients with isolated tongue base obstruction. Under local anesthesia, multiple lesions of the ventral tongue (genioglossus insertion) and dorsal tongue were given at each treatment session. A visual analog scale was used to assess changes in speech and swallowing. Polysomnography and Epworth Sleepiness Scale (ESS) were used to assess outcome. Patients were maintained on nasal continuous positive airway pressure after each treatment.

RESULTS: Patients received a mean 4.6 ± 0.6 treatments for a mean total of 7915 ± 1152 joules. There was no significant change in speech or swallowing at 3 months after completion of treatment. Patients reported a significant decrease in sleepiness with a mean change in ESS from 12.4 ± 2.9 to 7.3 ± 3.0 (P < 0.001). Mean apnea/hypopnea index decreased from 35.1 ± 18.1 to 15.1 ± 17.4 (P < 0.001). Transient mild to moderate pain and swelling occurred after each treatment. There were no significant complications (ulceration, paresthesia, infection).

CONCLUSION: TCRF can successfully treat the OSAS patient with tongue base obstruction. Combined treatment of the ventral (genioglossus insertion) and dorsal tongue appears safe and may improve outcome with less total energy when compared with traditional dorsal-only applications.

The mechanisms of obstructive sleep apnea (OSA) are well established. 1,2 Pharyngeal muscle relaxation during sleep leads to collapse of the upper airway. The palate and the tongue base are the most common sites of obstruction. Surgeons, in general, have been slow to recognize that OSA results from diffuse upper airway narrowing. In spite of the fact that only 25% of patients have isolated palate obstruction, uvulopalatopharyngoplasty (UPPP) continues to be the most common surgical procedure for OSA. 3 Aboussouan et al 4 has shown the cause of UPPP failure is untreated tongue base obstruction. We have shown that clinical outcomes can be significantly improved by combining surgical treatment for tongue obstruction, when indicated, with UPPP. 5 Unfortunately, surgeons are hesitant to perform tongue base procedures. The usual cited causes are lack of training, confidence, and increased risk.

The medical application of radiofrequency ablation (RFA) has been established over the last 3 decades, 6,7 In 1997, we reported results of a porcine pilot study and temperature-controlled radio-frequency volumetric reduction (TCRF) of the tongue. 8 The results suggested the potential role of TCRF in the treatment of OSA. This led to a prospective, nonrandomized clinical trial of TCRF of the tongue base for OSA. 9 Eighteen patients were enrolled in the study. The patients received a mean of 5.5 treatments at 4-week intervals for a mean total energy of 8500 joules. All treatments were in the area of the circumvallate papilla and tongue base. Outcome data showed a mean tongue volume reduction of 17% that resulted in a mean reduction in apnea/hyopnea index (AHI) from 39.6 to 18.6. Ninety-nine treatment sessions resulted in 1 tongue abscess. Postoperative antibiotics were not part of the study design. Woodson et al 10 recently reported on a multi-institutional study of tongue TCRF and OSA. Seventy-three patients were enrolled in this study with 56 (76.7%) patients completing the posttreatment evaluation (polysomnography). The group received a mean 5.4 treatments for a mean total energy of 13,994 joules. The mean AHI decreased from 40.5 to 32.8. A total of 335 treatments resulted in 8 infections. Postoperative antibiotics and steroids were a part of the treatment regimen.

Table 1.

Previous pharyngeal surgery

Surgical Procedure	Frequency	Percentage
UPPP	2	11
Phase 1	8	42
Hyoid, Phase 1	1	5
Phase 2	3	16
GA	1	5
None	4	21

Phase 1, UPPP + genioglossus advancement (GA); Phase 2, Maxillary + mandibular osteotomy.

The cited studies have focused treatment on the tongue base and circumvallate papilla area. This current study has included treatment in other areas of the tongue. The ventral surface of the tongue and the genioglossus insertion area have been emphasized. The question is posed, Can including treatment of the ventral surface of the tongue improve outcomes and reduce risk?

METHODS

Study Design

This is a prospective, nonrandomized, institutional review board (IRB) approved study. The inclusion criteria were individuals aged 18 to 60 with mild OSA AHI >10 to severe OSA. All patients had anesthesia risk group of ASA Class I, II, or III. Patients with AHI > 20 were required to be maintained on nasal Continuous Positive Airway Pressure (CPAP) during the treatment phase. The majority of the patients had previous unsuccessful airway surgery for OSA (Table 1). Airway narrowing and obstruction was limited to the hypopharynx. Pretreatment airway assessment included physical examination, cephalometric radiography, and fiberoptic pharyngolaryngoscopy. Nasal and palatal obstruction was ruled out by physical examination and fiberoptic examination. Patients with previous UPPP were assessed by the primary author (R.W.R.). Inclusion in the study required previous adequate tissue removal and no evidence of stenosis. Tongue base obstruction was determined by cephalometric radiography and fiberoptic examination. Pretreatment cephalometric analysis required a posterior airway space (PAS) less than 6 mm (normal, 10.5 mm ± 2). Fiberoptic examination demonstrated retrodisplacement of the tongue base and epiglottis against the posterior pharyngeal wall. The IRB protocol excluded patients of pediatric age, unstable medical or psychological problems (ASA Class IV, V) and preexisting speech and swallowing disorders. Patients underwent a series of TCRF under local anesthesia in an outpatient setting. The treatment interval was 4 to 6 weeks. The endpoint of the study was a total cumulative energy of less than 10,000 joules (5 treatments) or improvement in OSA symptoms. Posttreatment outcome data was accumulated at 3 months.

OUTCOME MEASURES

Standardized subjective self-reported outcomes were used to assess results and treatment effects. The Epworth Sleepiness Scale (ESS) is a validated instrument that reflects the chance of falling asleep in 8 common daily situations. Subjective sleepiness is reported by the patient on a scale ranging from no chance of dozing (0) to a high chance of dozing (3). A score greater than 8 would indicate sleepiness. Treatment effects were assessed using visual analog scales (VAS). A standard 10 cm VAS with anchors measured each subject's symptoms and assessments of speech and swallowing before treatment and at the conclusion of treatment. Scores ranged from 0 (best) to 10 (worst).

Objective outcomes were determined by attended level 1 polysomnography. Polygraphic monitoring included an electrocephalogram (C3–A2 and 02–A1 electrodes of the international electrode placement system), electro-oculogram, chin and leg electromyogram, electrocardiogram (modified V2 lead). Respiration was investigated by oral nasal airflow, thoracic and abdominal movements (inductive plethysmography, snoring sounds), subminiature electric microphone type MCE-2000 taped above the larynx, and oxygen saturation (pulse oximetry). Abnormal breathing patterns were scored using criteria for identifying sleep apnea and sleep hypopnea. An apneic event is cessation of breathing for greater than 10 seconds, and an hypopnic event is a 30% reduction in title volume of greater than 10 seconds accompanied by a 4% oxygen desaturation. Scored data include apnea-hypopnea index (AHI) and lowest oxygen desaturation (LSAT). Body mass index (BMI kg/m 2 ) was calculated before treatment and at the conclusion of treatment.

Fig 1.

Treatment area: A, dorsal tongue, B, ventra tongue.

TCRF TECHNIQUE

TCRF of the tongue was performed using the somnoplasty system (Gyrus-ENT, Memphis, TN). Radiofrequency is delivered at 465 kHz using a specifically constructed needle electrode and delivery system. The radiofrequency needle electrode has a 10 mm active length with a 10 mm protective sheath. Target temperature was 85° C. Joules per treatment site ranged from 400 to 750. An average of 3 lesions were created per treatment session. This included 1 to 2 lesions, midline or paramedian, at the tongue base-circumvallate papilla and 1 to 2 midline lesions of the ventral surface of the tongue (Fig 1). Local anesthesia was achieved by direct injection of 5 cc of 0.25% bupivacaine hydrochloride with epinephrine at each treatment site. Immediately before treatment, an additional 2 cc of 2% xylocaine hydrochloride with epinephrine was injected into each treatment site. Data accumulated include joules (watts/seconds) per treatment site, total joules, maximum temperature (degrees Centigrade), maximum watts, and treatment time. All patients were treated postoperatively with oral Keflex 500 mg 4 times a day for 3 days and Vicodin as needed. Steroids were not used. Patients were seen the day after treatment, at 4 weeks, or as needed to assess swelling, pain, and potential complications.

STATISTICAL ANALYSIS

All summaries of continuous variables are expressed as mean ± standard deviation (SD). Most continuous data were not normally distributed, so nonparametric tests were used. Differences between pre- and posttreatment variables were tested with the Wilcoxon signed-rank test. Differences between responders (AHI decreased by 50% or more) and nonresonders were tested with the Mann-Whitney U test. The data were analyzed with Intercooled Stata 7.0 software (Stata Corp, College Station, TX). A P value < 0.05 was considered statistically significant.

Table 2.

Demographic data

Age	49.5 yrs ± 10.7
Sex (% male)	79%
BMI (kg/m 2 )	30.0 ± 5.8
AHI	35.1 ± 18.1
LSAT	82.0 ± 8.7

RESULTS

Twenty patients were enrolled in this prospective review. Nineteen consecutively treated patients have completed treatment with postoperative evaluations. One patient failed to obtain a postoperative polysomnogram. Results are based on these 19 patients. The demographic information is included in Table 2. The mean age of the patients was 49.6 years ± 10.7. The group consisted of 15 males (79%) and 4 females (21%). As a group, the subjects were obese with a mean BMI of 30.0 ± 5.8. The group had moderate-severe sleep apnea with a RDI of 35.1 ± 18.1 and LSAT of 82.0 ± 8.7.

Treatment outcomes and parameters are summarized in Table 3. The group underwent an average of 4.6 treatments ± 0.6. The total joules delivered was 7915 ± 1152 that included 5636 ± 1042 to the tongue base and 2284 joules ± 589 to the ventral surface. The mean total joule per treatment was 1741 ± 224. The group, as a whole, showed significant improvement at 3 months. The AHI improved from 35.1 ± 18.1 to 15.1 ± 17.4(P < 0.001). The LSAT improved from 82.0 ± 8.7 to 86.3 ± (P < 0.01). As a result of treatment, the posterior airway space (PAS) improved from 4.3 ± 1.4 to 5.3 ± 1.7 (P < 0.05). The Epworth Sleepiness Scale decreased from 12.4 ± 2.9 to 7.3 ± 3.0 (P < 0.001). There was no significant change in the postoperative BMI that was 30.1 ± 5.8 (P > 0.3). VAS for speech was 1.2 ± 0.6 before treatment and 1.3 ± 0.6 at the conclusion of treatment (P > 0.3). VAS for swallow was 1.4 ± 0.6 before treatment and 1.4 ± 0.50 at the conclusion of treatment. There were no major complications in this study group (tongue abscess, airway compromise). There was one minor complication of transient tongue neuralgia that lasted 2 months.

Bivariate exploratory analysis of predictors of AHI response (ie, decreasing AHI by ≥ 50%) suggest that a lower preoperative AHI (P < 0.01) and a higher preoperative LSAT (P < 0.01) are each associated with AHI response. The responded, nonetheless, had at least moderate OSA (AHI 29 ± 14, LSA 85 ± 8). A lower preoperative age (P = 0.07) and a lower preoperative BMI (P = 0.08) may also be associated with AHI response, but they did not reach statistical significance. The amount of total energy did not predict treatment response (P > 0.1). Patients 9, 11, 15, and 17 had not had previous surgery for OSA. Patient 9, in retrospect, was not a good candidate for TCRF because of severe OSA and morbid obesity. There was no significant difference in treatment response between the group with previous OSA surgery versus no previous surgery.

DISCUSSION

The concept of treating the ventral surface of the tongue—genioglossus insertion—is based on the current knowledge of airway physiology in sleep-disordered breathing (SDB) and previously described surgical procedures. It is known that the genioglossus muscle determines tongue position. EMG activity of the genioglossus muscle is increased in the awake state and decreases during transition from wakefulness to sleep. Persons with sleep apnea during wakefulness have greater genioglossus EMG activity than people without sleep apnea. 11,12 We have previously described a surgical procedure that repositions the geniotubercle and genioglossus muscle. We have shown, polysomnographically, that surgical advancement of the genioglossus muscle can improve SDB. 13 This led us to theorize that producing volumetric contractions of the genioglossus muscle at its insertion can counteract the effects of loss of tone during sleep. This hypothesis appears to have validity. It further appears that patients required significantly less total energy (7900 joules/patient) than reported by Woodson et al 10 (13,900 joules/patient) and small amounts of energy on the ventral tongue (2000 joules/patient) affected outcomes.

The technique of administration was borne from previously cited papers. Powell et al 8 demonstrated in a porcine tongue model that RFA resulted in volumetric contraction and RFA energy directly correlated with lesion size. At approximately 800 to 900 joules, a lesion could be expected to be 1.2 cm 2 (R = 0.98). Using a 2 cm electrode (1 cm active), the lesion created could be safely below the tongue surface. In the discussion, they indicated that lesions of 600 to 750 joules were better tolerated with respect to pain and swallowing than a lesion of 800 to 1000 joules. Woodson et al 10 described a significant relationship between the volume of local anesthetic and electrolyte solution at the time of treatment and treatment outcomes. It has been shown that injection of an electrolyte solution at the time of treatment increased maximum lesion size. This formed the basis of injecting 2 cc of local anesthetic immediately before treatment and limiting energy delivery from 400 to 750 joules/lesion.

Table 3.

Treatment outcomes and parameters

	Pretreatment	RF Parameters (joules)	Post treatment
Patient	AHI	LSAT	BMI	Dorsum	Ventral	Total	No.	AHI	LSAT	BMI
1	14	90	27.8	4800	1600	6400	4	3	94	27.9
2	17	93	26.0	4700	1600	6300	5	4	94	26.1
3	29	90	26.0	6500	1600	6700	5	5	81	26.3
4	25	85	28.3	6700	1800	8500	5	8	87	28.6
5	62	81	28.9	6100	2700	8800	5	34	80	28.6
6	63	80	34.4	6400	2600	9000	5	32	84	34.0
7	20	85	39.5	7000	2200	9200	5	6	91	39.1
8	20	90	27.4	4800	1600	6400	4	4	96	27.4
9	72	70	46.1	7600	2200	9800	5	74	72	46.3
10	52	82	28.8	5800	2000	7800	4	13	85	29.0
11	25	83	22.7	5600	2400	8000	4	1	95	22.8
12	55	62	29.3	5400	2200	7600	4	23	78	29.1
13	33	64	31.9	4500	1800	6300	3	17	70	32.2
14	20	80	33.7	6200	2200	8400	5	9	85	33.5
15	24	90	26.7	5200	2800	8000	5	2	94	26.9
16	33	81	36.1	6900	3200	10000	5	19	88	36.5
17	18	87	24.8	4500	2200	6700	5	9	90	24.7
18	52	90	27.8	4200	3100	7300	4	2	92	28.0
19	33	78	24.1	4200	3600	7800	5	21	83	24.1
Mean	35.1	82.0	30.0	5636	2284	7915	4.6	15.1	86.3	30.1
SD	18.1	8.7	5.7	1042	589	1152	0.6	17.4	7.6	5.8

SD, Standard deviation.

Pazos and Mair 14 reported complications of radiofrequency ablation in the treatment of sleep disorder breathing. They described a significant complication rate in treating the base of the tongue with RFA. Twenty-five treatment sessions resulted in 8 (32%) significant complications. This included 4 patients with tongue neuralgias, 2 patients with severe floor of mouth edema, and 2 patients with tongue abscesses. Their technique involved treating 2 areas of the dorsum of the tongue with 750 to 1000 joules per treatment site. All patients were treated with oral antibiotics for 1 week and oral steroids for 5 days. As a result of these complications, their recommended avoidance strategy included antibiotics for 10 days and oral steroids for 5 days. Patients with moderate to severe OSA should be monitored overnight with pulse oximetry and nasal CPAP. Patients with airways rated ASA-III or greater should only undergo tongue base RFA with extreme caution. Patients with persistent complaints of dysphagia, odynophagia, globus, and neck or throat pain for longer than 1 week after RFA should undergo careful physical examination and potential scan. We did not experience the number of complications nor severity of complications that that Pazos and Mair experienced. In 87 treatment sessions, there were no serious complications. One patient experienced initial tongue pain after treatment that slowly resolved over approximately 6 to 8 weeks. There were no ulcerations, erosions, significant floor of mouth swelling, or abscesses. Approximately 50% of our patients returned to work the next day. RFA of the ventral surface appeared to be much better tolerated than the tongue base. There was minimal pain and mild-to-moderate swelling that resolved in 24 to 48 hours. All patients were treated with oral antibiotics for 3 days. This did not include oral steroids in any of the treatments. We do agree that patients with moderate-to-severe sleep apnea be maintained on nasal CPAP for airway protection after RFA of the tongue. Overnight monitoring does not appear necessary. We strongly recommend the use of oral ice chips immediately after RFA of the tongue and continued use for 24 hours.

CONCLUSION

This study demonstrates that TCRF tongue reduction reduces the severity of OSA. Antibiotics should be given after each treatment session and the use of oral steroids be avoided. Patients with moderate to severe sleep apnea should be maintained on nasal CPAP during treatment. The best candidates for TCRF are nonobese individuals with mild-to-moderate OSA; however, individuals with severe OSA may still be considered candidates. The limitation of this study are lack of a control group, small sample size, and short-term follow-up; however, the results of combined treatment of the ventral and dorsal surfaces of the tongue with TCRF are compelling.

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