Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common disorder that affects 2% to 4% of men and 1% to 2% of women between the ages of 30 and 69 years, and is increasingly becoming recognized as a major health problem.
Surgery with transoral robotic surgery (TORS) offers significant advantages compared with traditional open surgical approaches to the pharynx.
TORS allows for high-quality endoscopic optics for improved visualization with three-dimensional depth perception and robotic instrumentation.
The chief indications include a failed trial of continuous positive airway pressure, with polysomnographic evidence of moderate to severe OSAHS, in addition to daytime somnolence as documented through the Epworth Sleepiness Scale, with evidence of retrolingual collapse from a prominent base of tongue and/or prominent lingual tonsillar tissue.
The rate of success, defined as 50% reduction of preoperative apnea-hypopnea index (AHI) and an AHI less than 20, is achieved in up to 76.6% of patients.
Several surgical procedures have been developed to address tongue base obstruction, including tissue debulking procedures (midline glossectomy, radiofrequency ablation) and tissue repositioning (tongue suspension, genioglossal advancement, maxillomandibular advancement), each with varying results. The traditional external tongue base approach provides excellent exposure, although the potential for morbidity is significant. Minimally invasive transoral techniques include radiofrequency ablation, laser-assisted oropharyngeal surgery, submucosal minimally invasive lingual excision, and coblation endoscopic lingual lightening. There is limited evidence of their long-term efficacy, and suboptimal transoral access remains an issue. Base of tongue collapse is, therefore, challenging to address secondary to difficult surgical access and visualization along with uncertainty with regard to the volume of tissue that can be safely excised. Thus, there existed a critical need to improve surgical treatment of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) through either a shift in treatment paradigm or technological advances.
Robot-assisted technology was investigated as a means to overcome the surgical limitation associated with current technologies. Transoral robotic surgery (TORS) for resection of oropharyngeal and supraglottic neoplasms using the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA) was pioneered by Weinstein and O’Malley in 2006. In 2009, the US Food and Drug Administration (FDA) approved TORS for benign and malignant lesions of the tongue base. This technique was extended to transoral resection of the base of tongue and supraglottoplasty in patients with OSAHS by Vicini and colleagues in 2009, and in 2014 the FDA approved TORS procedures for benign base-of-tongue resection procedures after its safety and feasibility in patients with OSAHS were shown. Since then, it has been shown to be an effective treatment option for both solely base-of-tongue procedures and when combined with multilevel surgery. TORS has the ability to overcome the issues with surgical access that had previously hampered surgical treatment options. The robot system allows for high-quality endoscopic optics for improved visualization with three-dimensional (3D) depth perception and robotic instrumentation. The instruments have 6 degrees of freedom and 90° of articulation, which provides superior dexterity and precision. At this time, it is estimated that more than 450 TORS procedures for OSAHS have been performed throughout the world.
The chief indication for surgery in OSAHS is that the patient has failed a trial of continuous positive airway pressure (CPAP) either because of noncompliance or inability to tolerate the device. Typically, the patient should have polysomnographic evidence of moderate to severe OSAHS in addition to daytime somnolence as documented through the Epworth Sleepiness Scale. For TORS-specific surgery, patients should have evidence of retrolingual collapse from a prominent base of tongue and/or prominent lingual tonsillar tissue, which is determined either by awake nasopharyngoscopy or drug-induced sleep endoscopy. Most patients are overweight men, but patients with a preoperative body mass index (BMI) less than 30 kg/m 2 are preferred. Mouth opening measured as interincisive distance of 25 mm or more is a prerequisite for sufficient exposure. The aim of these surgical procedures is to enlarge the airway space and/or increase the muscular tension around the retroglossal region by reducing soft tissue volume or by altering the facial skeleton framework.
Contraindications for TORS are classified as patient compliance, patient anatomy, and medical comorbidities. If the patient is compliant with CPAP, or in those who have not yet tried CPAP, surgical intervention is discouraged. A degree of trismus or limited mobility of the neck may make the base of tongue inaccessible. Significant micrognathia and macroglossia may also limit the exposure for TORS procedures. Dynamic compression of the lateral airway from soft tissue is a relative contraindication because TORS essentially addresses only anterior-posterior collapse of the airway. An American Society of Anesthesiologists (ASA) score greater than 2 with particular reference to significant or unstable cardiovascular disease or the need for anticoagulation must be treated with caution. Patients with any degree of dysphagia (unless secondary to lingual tonsillar hypertrophy), swallowing complaints, or psychiatric illnesses should also not be considered for TORS.
The base of the tongue has a rich vascular supply from the lingual artery. Significant vessels are located laterally and inferiorly. The average length of the lingual artery as visualized by computed tomography angiography is 101.24 ± 16.99 mm. The dorsal lingual artery is the major branch that arises from the lingual artery, usually below the hyoglossus muscle. At the level of the hyoid bone, it is located above it and medial to the hypoglossal nerve. Inferiorly located, with regard to the artery, lies the lingual vein, which, in turn, accompanies the hypoglossal nerve, which is invisible preoperatively and intraoperatively. The medial region of the tongue base is without major vessels. There are numerous small branches from the lingual artery approaching the midline. These branches can be used as a safe plane to remind the surgeon to be extremely careful when dissecting deeper.
The foramen caecum linguae is an important anatomic landmark for midline partial glossectomy surgery. Anatomically, the foramen caecum linguae is located at the one-third middle and posterior junction. The average distance from the foramen caecum to the hypoglossal/lingual artery neurovascular bundle was 1.66 cm in a cadaver study, and 1.68 cm in a study using computed tomography angiography. The average distance between 2 lingual arteries at the foramen caecum of the tongue was 27.78 ± 6.57 mm, and the distance to the surface of the tongue was 29.27 ± 5.39 mm. Therefore, 15 mm and 20 mm are used as the surgical functional zone based on the average distance and 95% confidence interval for the distance between bilateral lingual arteries and arteries to the tongue surface, respectively.
Lingual tonsils are parts of the Waldeyer ring along with the palatine tonsils, adenoids, tubal tonsils, and lateral pharyngeal bands. Lingual tonsils are situated at the base of tongue and bounded by the epiglottis posteriorly, circumvallate papillae anteriorly, and tonsillar pillars bilaterally.
Patient preparation and positioning
An appropriate mouth gag is chosen to provide adequate exposure to the anatomic structures without compromising the workspace necessary for the robotic arms and instruments. The authors use the Davis Meyer (Karl Storz, El Segundo, CA) retractor, which includes multiple tongue blades of different lengths. The surgery is performed with the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA). The required robotic instrumentation includes the high-definition camera and the EndoWrist instruments (Intuitive Surgical, Sunnyvale, CA). The binocular camera provides magnification of up to 10 times, which results in a 3D high-definition image that allows easy identification of vessels and nerves. It is available in 12-mm and 8-mm diameter scopes, both of which provide excellent optics while providing adequate working space in the mouth. Two 5-mm articulated EndoWrist instrument arms are typically used. These instrument arms provide 180 ° of articulation and 540 ° of rotation, tremor filtration, and amplitude scaling, and allow bimanual tissue manipulation in multiple planes. Typically, a 5-mm Maryland forceps is placed in one arm and the spatula-tip monopolar cautery in the other for dissection and coagulation ( Fig. 1 ).
It is imperative to have ready sufficient overhead lighting, a Yankauer suction, an additional cautery device, appropriate-length forceps, hemostats, Metzenbaum scissors, and other basic soft tissue instruments ( Fig. 2 ). The patient gurney should be centered with the surgeon console approximately 1.8 to 2.1 m (6 to 7 feet) away. The surgeon console should be situated on the same side of the operating table as the assisting surgeon to allows for easier communication between the assistant and the console surgeon. The anesthesia cart is placed at the foot of the bed (patient’s head is turned 180 ° from anesthesia) and the assistant is seated at the head of the patient to provide suctioning and assistance with cauterization. The scrub nurse stands alongside the patient cart opposite the robotic console. Difficult-airway equipment, including a fiberoptic endoscope or GlideScope (Verathon Medical, Bothell, WA), must be readily available.
The primary surgeon is seated at the robotic console, which is typically in close proximity to the operating room table. The console affords a 3D view of the surgical field and allows manipulation of the 2 robotic arms and the camera www.intuitive.com/en/products-and-services/da-vinci . The surgical assistant supports the primary surgeon by retracting tissues, creating a smoke-free environment, and suctioning blood to aid visualization. As needed, the assistant helps with adjusting the robotic arms and camera to prevent collisions, as well as facilitate hemostasis. There is an integrated microphone-loudspeaker system inbuilt in the robotic system that aids communication between the primary and assistant surgeon. The surgical scrub aids in passing instruments and providing equipment as needed but may also provide assistance with suctioning. It is imperative that the surgical scrub is familiar with the TORS setup to aid in decreasing both setup and operative time. The assistant surgeon and the surgical scrub can see a two-dimensional representation of the surgeon’s view on the slave monitor, which is attached to the robot in the da Vinci S HD model and to the control tower–vision cart in the Si model.
The patient is positioned supine and the upper airway is anesthetized with topical lidocaine. The patient is then intubated with a nasotracheal tube and the operating table is turned 180 ° from the anesthesia cart ( Fig. 3 ). A 2-0 silk stitch is placed in the anterior portion of the tongue to assist in retraction and positioning of the tongue. The mouth gag is placed to provide adequate exposure of the base of the tongue. At this point, the surgical bed is lowered to the lowest position possible. A Mayo stand without the accompanying tray should be placed over the patient’s head so that the curved end of the retractor blade can be connected to the Mayo stand, and the stand elevated to help hyperextend the neck ( Figs. 4 and 5 ). The robotic patient side cart is wheeled to the patient’s head so that the base of the cart is approximately on a 30 ° angle with the base of the surgical bed. The robotic base may come from either the left or right side depending on the room setup.