Background

Total laryngectomy, as first described in 1873 by Billroth, became the mainstay of treatment for all laryngeal cancers for the better half of the twentieth century. ¹ However, the surgical management of laryngeal cancers has undergone great evolution, with progressively sophisticated open and endoscopic techniques available for individualized treatment of patients. Technological advances in radiologic imaging and surgical instrumentation are largely responsible for facilitating more tailored approaches. Furthermore, an understanding of the essential structural elements necessary for laryngeal function has allowed for more conservative techniques ranging from open conservation partial laryngectomies to endoscopic resections.

Transoral endoscopic laryngeal cancer surgery has developed in an effort to reduce morbidity compared to traditional open laryngeal surgery, while maximizing oncologic outcomes. Although these approaches cannot replace all open techniques, for selected cases they provide a minimally invasive approach, with optimal functional outcomes and equivalent oncologic results. ² , ³ Radiation as primary therapy has also made great strides in preserving laryngeal function. In advanced-stage cancer, multimodality treatment including surgery with radiation can be expected to achieve similar oncologic outcomes to radiation and chemotherapy, and thorough patient evaluation with a multidisciplinary team must be exercised to arrive at the optimal treatment selection on a case-by-case basis.

Line-of-sight transoral laser microsurgery (TLMS) using binocular microscopy and laser ablative instruments has been employed for over three decades. ⁴ , ⁵ , ⁶ In select laryngeal cancer patients this technique can achieve cure with excellent voice and swallowing preservation and has a proven oncologic record. However, limitations of this approach include a steep learning curve, need for frequent repositioning of the laryngoscope for larger tumors, lack of bimanual instrumentation, and need for dedicated pathologic assessment of margins. These factors have precluded the widespread, enthusiastic adoption of this challenging technique beyond highly specialized centers.

The concept of using the da Vinci surgical robotic system (Intuitive Surgical, Inc.) for transoral robotic surgery (TORS) of the larynx was introduced in 2005 and has evolved since. ⁷ , ⁸ TORS shows promise in overcoming some of the limitations of line-of-sight endoscopic laryngeal surgery mentioned above. ⁹ , ¹⁰ The articulated, wristed instruments with tremor filtration, motion scaling, and 540° of motion provide precise bimanual tissue manipulation in areas heretofore inaccessible. Also, the robot is not constrained by line-of-sight issues and provides a remarkable three-dimensional view with an endoscope that can be advanced into the oropharynx. However, the robot is limited by its size in its ability to access lesions inferior in the larynx. Therefore, TORS with the da Vinci system has been used primarily for supraglottic laryngectomies, which will be the primary focus of this chapter. It should be noted, however, that a new surgical system (Flex Robotic System, Raynham, MA) is designed to reach into the hypopharynx and larynx and shows promise accessing areas beyond what the da Vinci can reach. Intuitive Surgical, Inc., will also be unveiling a new generation, single port (Sp) system in 2017. This system holds great potential, especially for natural corridors, notable transanal colorectal surgery, and transoral surgery. Federal Drug Administration (FDA) approval for head and neck surgery is anticipated in 2018. As with the Flex Robotic System, the Sp has potential to expand transoral surgical capabilities in the larynx and hypopharynx.

TORS is an innovative and promising new approach for treating laryngeal cancer. A thorough understanding of endoscopic laryngeal anatomy is mandatory for mastering this technique. In this chapter we will discuss the indications, advantages, and limitations of endoscopic laryngeal surgery with the da Vinci robotic surgical system; review the current literature examining the outcomes of TORS in the management of laryngeal cancer; and describe endoscopic laryngeal anatomy and the TORS technique.

Indications

Extrapolating from TLMS approaches, laryngeal cancer surgery using TORS may be indicated for both glottic and supraglottic tumors. ² Tumor characteristics are evaluated by neck computed tomography (CT) with intravenous contrast, in-office flexible laryngoscopy, and direct laryngoscopy performed prior to definitive surgery. Early-stage glottic tumors without subglottic extension or posterior extension beyond the vocal process are most amenable to endoscopic surgery. ² Traditionally, tumor involvement of the anterior commissure has made exposure challenging, but the enhanced field of view and instrument maneuverability of the robot may expand indications for treatment of this site. However, using the robot to access this area is not possible in many patients because of its size. In the supraglottis, T1 and T2 tumors are amenable to endoscopic approaches, as are select T3 tumors that require resection of the paraglottic and/or pre-epiglottic space but do not involve the cricoarytenoid joint.

Although TORS may improve the visualization and dissection of larger laryngeal tumors, any tumor invasion through the laryngeal cartilaginous framework is a contraindication to endoscopic laryngeal approaches, as the soft tissue extension of tumor beyond the larynx cannot be treated adequately by a closed approach. In the supraglottis, tumor involvement of both arytenoids precludes an endoscopic or open partial laryngectomy approach, as the functional larynx requires preservation of at least one cricoarytenoid unit.

Appropriate patient selection also requires a preoperative medical assessment with particular attention to preexisting cardiopulmonary conditions. As with open partial laryngectomy techniques, a certain degree of aspiration must be tolerated after surgery, and therefore adequate pulmonary functional reserve must exist. A thorough preoperative physical examination should include an evaluation of neck range of motion (ROM), dentition, and mouth opening. Oral access can be further assessed during the time of diagnostic direct laryngoscopy as described in the following paragraphs.

Endoscopic Laryngeal Anatomy

Here we focus on the neurovascular landmarks that are encountered during a transoral resection of supraglottic tumors. The superior laryngeal artery (SLA) is the main artery for perfusion of the supraglottis. It enters the thyrohyoid membrane and divides into branches supplying the paraglottic and pre-epiglottic spaces, the epiglottis, arytenoids, and aryepiglottic folds. Preemptive identification and control of the SLA pedicle makes for a hemostatic surgical field, which is critical in the limited space of endoscopic supraglottic surgery, as well as for protection from life-threatening hemorrhage postoperatively. Although branches of the SLA anastomose with dorsal branches of the lingual artery, the lingual artery proper is not typically encountered during this surgery.

Goyal et al elegantly describe a cadaveric anatomical dissection of the supraglottic larynx performed using the da Vinci robotic system. ¹¹ Standard robotic setup is described in the following section. After adequate exposure of the supraglottic larynx is achieved using the Feyh-Kastenbauer (Gyrus Medical, Maple Grove, MN) or Flex Retractor (MedRobotics, Raynham, MA), an incision can be made through the mucosa overlying the median glossoepiglottic fold and extended laterally toward the lateral glossoepiglottic fold. Upon incision of the lateral glossoepiglottic fold, the middle pharyngeal constrictor muscle is identified and followed to its insertion anteromedially along the hyoid bone ( Fig. 6.1 ). The greater cornu of the hyoid bone is identified. The middle pharyngeal constrictor and suprahyoid musculature lateral to the greater cornu are released ( Fig. 6.2 ). The tendinous hyoid insertion of the anterior and posterior digastric muscle bellies is also seen. The hyoid bone is retracted medially, and the superior laryngeal neurovascular bundle comes into view. The SLA and internal branch of the superior laryngeal nerve (ibSLN) are identified here, entering the thyrohyoid membrane just inferior and anterior to the greater cornu of the hyoid ( Fig. 6.3 ) and superior and anterior to the superior cornu of the thyroid cartilage within the paraglottic space. Medial to the hyoid bone the intralaryngeal SLA and ibSLN can be followed in the pre-epiglottic fat, where the superior branch of the SLA courses toward the epiglottis and vallecula. It can be identified near the junction of the epiglottis and lateral glossoepiglottic fold. The superior branch may be the most superficial branch of the SLA encountered during supraglottic surgery, as it courses through the aryepiglottic fold. Additionally, a posteromedial branch of the SLA may be seen traveling toward the arytenoid. An anterior branch of the SLA travels within the paraglottic space, heading toward the superior border of the thyroid cartilage. In addition to these clinically relevant branches, dorsal branches of the lingual artery also supply the pre-epiglottic space.

The ibSLN is the most important nerve branch to the supraglottic larynx. It is described as having three divisions: superior, middle, and inferior. The superior division innervates the epiglottis and lateral glossoepiglottic fold. The middle division innervates the aryepiglottic fold and supraglottis to the level of the vestibule. The inferior division innervates the piriform recess, arytenoid, and posterior portion of the aryepiglottic fold. Compared to open supraglottic laryngectomy, endoscopic supraglottic techniques may preserve the ibSLN more proximally, resulting in improved functional outcomes, as more sensory innervation to the supraglottic larynx is preserved.