Transoral robotic surgery is now a well-accepted technique in malignant tumours of the tongue base. Here the team from St Mary’s and the Royal National Throat Nose & Ear Hospital in London describe its use in carefully selected patients with sleep-disordered breathing.
Sleep-disordered breathing (SDB) is used to describe a spectrum of abnormalities ranging from primary snoring to upper airway resistance syndrome and obstructive sleep apnoea (OSA). OSA is an underestimated but serious social health problem affecting at least 2-4% of the adult population.
In contrast to primary snoring, OSA is associated with high morbidity and mortality. There is a clear positive correlation between OSA severity and both cardiovascular and neurocognitive events.
The gold standard treatment for moderate or severe OSA is continuous positive airway pressure (CPAP) although compliance rates range from 28% to 80% . For patients not able to tolerate CPAP an alternative treatment is required, of which surgery may be an option. The existing surgical treatment options have demonstrated variable success, particularly when multi-segmental and involving the tongue base and epiglottis .
The base of the tongue (BOT) is recognised as a significant site of obstruction in many patients suffering from OSA . The presence of multiple surgical measures aimed at improvement of tongue base obstruction validates the failure of a ‘one size fits all’ approach to the BOT. A lack of precision and focus often results in inadequate BOT surgery. In addition, difficulty in access and patient physiognomy makes BOT surgery a difficult challenge. Minimally invasive techniques have proven inadequate when treating patients with moderate-severe BOT hypertrophy. Furthermore, traditional open tongue base approaches are associated with significant morbidity and remain unacceptable to patients with OSA .
Transoral robotic surgery (TORS) addresses the difficulty with operative exposure of the tongue base. It permits greater dexterity, precision and surgical access to the BOT. The robot system provides improved visualisation with three-dimensional (3D) depth perception and robotic instrumentation, in addition to tremor filtration and motion scaling. On the other hand, potential disadvantages include lack of tactile or haptic sensation and exorbitant capital cost.
The concept of TORS as a treatment of OSA was first introduced in 2010 by Vicini et al.  as a transoral robotic modification of Chabolle’s open tongue base reduction and hyoid epiglottopexy . It has now been shown to be an effective treatment option for OSA patients [5-7].
TORS indications – St Mary’s / RNTNEH protocol
Patient assessment for TORS is paramount in order to improve the possibility of surgical cure and avoid unnecessary operations. Patients eligible for TORS are those who have polysomnographic evidence of moderate-severe OSA with daytime somnolence documented by the Epworth Sleepiness Scale (ESS) and a body mass index (BMI) of less than 35kg/cm2.
Only patients that have tried and previously failed or refused treatment with CPAP are deemed suitable. Airway endoscopy, both awake and under drug-induced sedation, allows obstruction at the level of the BOT and / or epiglottis to be diagnosed. Drug-induced sedation endoscopy (DISE) provides a dynamic, three-dimensional and real time evaluation of the anatomical sites of upper airway collapse. It has been found to be a reliable and consistent clinical tool for assessing the anatomical site of airway obstruction during sleep.
Patient anatomical features such as neck circumference, mouth opening, mandibular width and length, hyoid-mental length and Mallampati grade are all assessed preoperatively, as they may determine patient suitability for TORS.
TORS set-up and surgical procedure
The TORS set-up has been previously described for BOT neoplasms. The operating surgeon sits at the operating console, which should be situated on the same side of the operating table as the assisting surgeon to allow easier communication within the theatre team. The assistant surgeon is seated at the head of the patient to provide suction, assistance with retraction of tissues and adjustment of robotic arms and instruments. The Da Vinci robot is docked at an angle of 30°-45° relative to the base of the surgical bed.
The patient is positioned supine with a shoulder roll and head ring. Nasotracheal intubation is performed when possible to permit unrestricted and clear access to the tongue base and epiglottis during surgery. St Mary’s TORS set-up is shown in Figure 1.
Figure 1: TORS set-up using the standard da Vinci system.
A = 30° up 8 or 12mm dual channel endoscope;
B = 273µm thulium laser; C = 5mm long tip Maryland dissector; M = patient’s mouth.
Tongue base reduction
There are different techniques described in the literature when performing BOT reduction. Vicini performs an inverted pyramid technique , whereas Friedman prefers a triangular resection method . The incision starts in the midline and extends from the foramen caecum and circumvallate papillae to the vallecula, permitting sparing of a 1cm mucosal bridge between the base of the epiglottis and the tongue interface (Figure 2). At St Mary’s, resection is carried out by means of 273μm thulium laser fibre ablation (2013 nm, 15W). The limits of resection are from the midline extending posterior to the circumvallate papillae for a distance of 2cm towards the vallecula. The resection then continues for 1cm either side of the midline to a depth of 1cm (Figure 2). The lateral limits of the resection are at these limits in order to avoid damage to the lingual artery.
I. TBR: marking area for laser ablation
II. TBR following ablation
III. Partial epiglottic resection
IV. Completed epiglottoplasty
Figure 2: Tongue base reduction and epiglottoplasty (e = epiglottis, b = base ot tongue).
The epiglottis is grasped with the Maryland dissector and a wedge-shaped part of the upper one-third of the epiglottis is resected using the thulium laser fibre (Figure 2). The plane of resection is above the pharyngoepiglottic folds to minimise the chance of aspiration and to avoid bleeding from branches of the superior laryngeal vessels.
Intra- and postoperative management
Mean set up time is 19.5±10.5 min and mean operative time for BOT reduction is 26.5±9.2 min and for epiglottoplasty is 10.4±4.9 min . The average amount of removed tissue from the BOT is 10.3±4.1ml. Blood loss is minimal and patients receive perioperative and postoperative steroids to minimise lingual edema, nausea and pain. In addition, antibiotics and analgesics are given postoperatively (Table 1). Soft oral diet is allowed a few hours after surgery for most patients, although some centres use a nasogastric tube for all patients in the immediate postoperative period. The average hospital length of stay is 3.5±3.2 days with a wide range (1-19 days), reflecting the different hospital policies in different centres. In our unit, the first two patients stayed hospitalised for 48 hours as a matter of precaution but the remaining cohort (19/21 patients, 90.5%) were all discharged within 24 hours. The disposable costs for TORS are estimated to be approximately £1000 a case.
Outcomes and complications
TORS is an effective treatment option for surgery to the BOT and epiglottis. Success rate ranges from 45% to 90%, with success defined as a decrease in postoperative apnoea-hypopnoea index (AHI) of greater than 50% and a postoperative AHI of less than 20 episodes per hour [5-9]. A large multicentre study demonstrated a mean success rate of 66.9%, and 53.8% of patients had an AHI of less than 15 episodes per hour and did not require CPAP after surgery . Statistically significant improvement was also seen in ESS score, lowest oxygen saturation, and overall patient satisfaction and quality of life score. No major complications relating to tongue mobility, hypoglossal nerve injury, lingual artery injury or speech have been noted so far. Likewise, no aspiration symptoms have been reported after epiglottoplasty. The most common operative complications are transient dysgeusia (14%), bleeding (5%) which was self-limiting in most cases, and temporary tongue numbness caused by pressure from the tongue blade attached to the mouth gag (100%, typically resolved within 1-4 weeks) . Other potential complications include transient dysphagia (5%) and transient pharyngeal oedema (0.4%).
Most patients with OSA benefit from the use of the gold standard therapy of CPAP. However, because of the morbidity and mortality associated with moderate and severe OSA, noncompliant patients should be considered and assessed as to whether surgery might offer an alternative treatment. The literature would support that TORS may have a role in selected patients. Although the application of TORS for OSA is still in its infancy, the results so far are promising. TORS allows the surgeon to address BOT obstruction with excellent visualisation and an easier approach that is well tolerated by the patient.
Patient selection has a pivotal role as TORS certainly does not proclaim to offer a ‘one-size fits all’ surgical solution for OSA. DISE evaluates the pattern of collapse in each patient before selecting and planning patients for surgery. Previous studies have shown that at least 25% of patients with moderate-severe OSA have significant BOT and supraglottic obstruction that is suitable for TORS.
TORS for OSA may be a stand-alone procedure addressing obstruction at the level of BOT and / or epiglottis or can be carried out as part of multilevel surgery that may include either palatal and / or nasal surgery. Furthermore, recent studies demonstrate that TORS can be feasibly performed without the need for tracheostomy .
In conclusion, patients who undergo TORS with or without concomitant procedures had a significant improvement in objective and subjective OSA parameters and symptoms. TORS should be considered as an additional option for treating OSA related obstruction at both BOT and epiglottic levels. It has been associated with good efficacy and low complication rates. Currently, there are limited data to support its long-term efficacy and further studies are needed to elucidate its position in the surgical management of OSA patients.
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Declaration of competing interests: None declared.