Transoral endoscopic laser laryngeal microsurgery depends upon the ability of the surgeon to determine the extent of tumor invasion prior to excision via detailed physical examination performed under general anesthesia and imaging studies. The primary objective is to achieve complete resection of the cancer with clear margins, while maintaining as much organ function as possible (e.g., swallowing, speech, etc.). While transoral laser laryngeal microsurgery (TLM) has many advantages such as decreased post-operative morbidity, reduced recovery time and the potential for organ preservation, recurrence or incomplete resection are significant risks. Hence, the procedure requires skill and sound clinical judgment. It is generally contraindicated in patients with known extensive invasion into other structures and recurrent cancer in previously irradiated areas.22

The CO₂ laser has a firmly established role in the treatment of benign laryngeal disorders such as papillomas, polyps, vascular malformations and strictures. Since Jako and Strong first introduced the CO₂ laser in 1970, several groups, including those led by Shapshay, Zeitels, Ossoff, Steiner, Motta and Rudert, have published extensively on their experiences with laser surgery in benign laryngeal disease.37 The use of other lasers such as the KTP(Nd:YAG) laser, the pulsed dye laser and the diode laser has also been reported, but their use has not been as widespread due to lack of availability in most medical centers. Therefore, the carbon dioxide laser remains largely the laser of choice.

In the pre-operative evaluation, patients always undergo an indirect mirror or a flexible fiberoptic laryngoscopy examination to determine the extent of the lesion and vocal cord mobility. Video stroboscopy of the vocal cords may be included in the pre-operative evaluation to determine the dynamics of vocal cord movement. Some patients may undergo diagnostic imaging (CT or MRI of the neck) to determine the extent of disease. Vocal cord polyps warrant a trial of speech therapy for vocal coaching and training in proper voice use prior surgery. Patients with carcinoma of the larynx, recurrent papillomatosis and Reinke’s edema must be strongly encouraged to quit smoking.

The most common parameters for the CO₂ laser beam using a micromanipulator is a 250 μm spot size with a working distance of 350 mm. Laser power is usually below 8 W. In the superpulse mode, where exposure time is 0.1 s or less, a low power setting of 2–3 W is used. The superpulse mode is useful in achieving maximum ablation through minimal penetration and maximum energy absorption at the surface of interest. There is almost no charring due to the minimal thermal diffusion in the surrounding areas around the target. In preparation for incision of epithelium in cases such as Reinke’s edema, microvascular coagulation is required. The laser is typically set for a 0.05 s pulse of 1 W of power using an unfocused beam.20 Recently, flash scanner technological originally developed for use in dermatologic applications has been re-purposed and adapted for use in laryngeal microsurgery. These devices allow creation of user-defined ablation patterns and cuts under precise computer control. The high cost of these systems has limited the broad adoption of this technology (Acublade-SurgiTouch system, Lumenis, Santa Clara, CA).

Suspension microlaryngoscopy provides a method in which the surgeon is able to directly visualize the larynx and its surrounding structures. Gustav Killian was among the first to describe suspension laryngoscopy in 1912 and later developed the Killian-Lynch suspension laryngoscope along with Robert Clyde Lynch. Zeitels showed effective use of suspension laryngoscopy in 120 cases in a prospective assessment.43 Suspension allows for bimanual direct laryngoscopic surgery.44 Furthermore, suspension laryngoscopy permits the use of a laryngoscope with a larger bore thereby enhancing exposure. Figure 7 demonstrates the positioning of a patient in suspension, and Fig. 8 shows the normal anatomy of the larynx as visualized under suspension microlaryngoscopy.

With the patient anesthetized and lying supine, the head is fully extended. A rigid laryngeal endoscope is introduced through the oral cavity and past the epiglottis into the larynx until the desired endolaryngeal structures are visualized. The vocal cords should be clearly visualized from the anterior commissure to the vocal process on both sides. The rigid laryngoscope is then stabilized and secured using a suspension arm. Surgery is performed using a microscope with a 400 mm focal length lens or using a Hopkins rod endoscope inserted thru the laryngoscope bore. There are several instances that make suspension microlaryngoscopy very difficult or even impossible. Abnormal anatomy such as a short, stiff neck, long or protruding maxillary teeth, displaced larynx and lesions or a mass at the base of tongue may limit and prevent suspension laryngoscopy in these patients.42

Suspension laryngoscopy provides a direct airway in which anesthesia may be administered either through an endotracheal tube that is inserted parallel to the laryngoscope or via jet ventilation. This direct airway also provides an unimpeded path for the surgeon to access the vocal cords and other structures in the larynx. The rigid laryngoscope also prevents collapse of the pharynx and hypopharynx that would then obstruct the surgeon’s view. The greatest advantage that suspension laryngoscopy provides is that it allows for a minimally invasive approach to laryngeal surgery where traditional approaches have involved large external incisions and significant morbidity.

Since Jako coupled the carbon dioxide laser to the operating microscope in 1972 for laryngeal surgery, the CO₂ laser has been the wavelength of choice. The CO₂ laser is used in the majority of operations because of its widespread availability in most medical centers and its efficiency in simultaneously cutting tissue and maintaining hemostasis. Other commonly used lasers in otolaryngology include the KTP(Nd:YAG) laser and the argon laser. In laryngeal surgery, the CO₂ laser is generally coupled to a micromanipulator attached to the microscope. This allows the surgeon to use microsurgical instruments and the laser at the same time. It also provides maximum surgical field visualization with high magnification and an unobstructed view of the lesion. The CO₂ laser has several advantages over conventional surgical instruments that cut or cauterize in that traditional devices may obstruct the field of view or amplify the surgeon’s intention tremor via a lever arm of up to 20 cm. Furthermore, post-operative edema is less with CO₂ laser endoscopic surgery compared to non-laser methods, and thus reduces the risk of post-operative airway obstruction and subsequent tracheostomy. Diminishing the amount of edema also improves the patient’s post-operative swallowing function. The thermal damage zone when using micromanipulators introduces limited artifact into the histological assessment, and it coagulates small blood vessels and seals lymphatic channels thus minimizing the incidence of metastases.20 The diameter of the laser beam, pulse duration and irradiance can be adjusted to produce different tissue effects. Spot sizes between 1 to 4 mm are used for tissue ablation and 0.2–1 mm used for cutting with powers varying anywhere from 2 to 10 W. Some micromanipulators further focus the beam down to an even smaller spot size, and combined with short pulse durations or flash scanner technology, can ablate tissue with minimal to no charring just as in skin resurfacing.45 Morbidity of using the CO₂ laser when appropriate is far less than cold surgery, and the cost effectiveness is much greater.46

In certain cases where lesions extend out of the surgeon’s visual field, the CO₂ laser can be delivered by a flexible hollow waveguide. However there are limitations with the use of the hollow waveguide due to its limited angulation, the diameter of the laser spot and the significant and variable loss of power during transmission.20 Regardless, recent techniques using hollow fiber technology are evolving.47–51

Patients who are otherwise healthy and undergo a limited resection are routinely given a single dose of intravenous steroids, observed in the post-operative care unit and discharged on the same day. Patients who have multiple medical problems or have more extensive surgical excisions, and therefore have a higher possibility for airway compromise, are admitted overnight at minimum for airway observation and scheduled steroid dosing. Post-operative antibiotics are not routinely administered. Strict voice rest for the first 48 h is observed followed by modified voice rest (no screaming, no whispering, limited talking) for the next 2 weeks. Patients are then monitored in clinic with repeat flexible fiberoptic laryngoscopy exams. Any change in voice, difficulty breathing or weight loss is monitored closely and may necessitate repeated exams and procedures.

In general suspension laryngoscopy is safe for patients as long as the patient has gone through proper pre-operative evaluation by the otolaryngologist and anesthesiologist.42 Compli­cations associated with TLM are more pertinent to the use of the laryngoscope instead of the actual laser itself. Difficult intubation or forceful endoscopic suspension can easily chip, loosen, or fracture teeth if the surgeon is not careful with the orientation of the laryngoscope in the oral cavity. In a study of 339 microlaryngoscopy patients, 75% were found to have small mucosal lesions of the oral cavity, oropharynx and lip.57 Though the injuries were minor, they were a source of major complaints for the patients but resolved over a period of several days. Other complications associated with laser microsurgery include lingual and hypoglossal nerve palsy. Prolonged displacement of the tongue can cause severe contusion and swelling that often leads to dysphagia and sometimes-permanent dysesthesia (sensory disturbance) in the tongue.

There are many general safety considerations involving the use of surgical lasers in surgery that were discussed earlier in this chapter. In particular to laryngeal surgery where high-powered lasers are used in small confined areas with flammable gas, the use of caution cannot be emphasized enough. Stray laser light is not a rare event and is capable of causing burns in unwanted areas. It is recommended practice to cover areas beyond the target site to protect from unwanted burns. Control of oxygen content, inhalation agents, and use of special laser endotracheal tubes in these procedures is important.

Though TLM rarely requires tracheotomy post operatively, it is nevertheless a real possibility in the intermediate and advanced cases. Surgeons must always be aware of certain indicators for tracheotomy. Prolonged compression of the tongue during TLM can cause lingual edema that can lead to airway compromise. Sudden secondary hemorrhage is a major risk in TLM and often necessitates a tracheotomy. Large arteries and vessels should not only be cauterized but clipped as well to avoid sudden secondary hemorrhage.

TLM typically causes the formation of large granulomas if cartilage is exposed by the surgical procedure. These granulomas are perpetuated by small osseocartilaginous sequestrae unless they are removed.22 TLM involving the anterior commissure often results in a round anterior glottic effect, and this often leads to breathiness and hoarseness.58

Laser surgery for benign lesions in the larynx is relatively safe compared to most other treatment modalities. It is a minimally invasive technique with almost no complications attributed to the laser itself.

Future directions of laser use in laryngology involves new devices for delivery, office based laser applications, the use of the laser for welding tissue and the creation of lasers that are even more precise than those which are currently available. A recent technological advance (Omni Guide, Boston, MA) has provided surgeons the use of CO₂ lasers through a flexible fiber. The Omni Guide Beam Path uses a hollow “photonic band gap fiber.” The fiber is placed in a handpiece coupled with a suction that eliminates the need for a micromanipulator and allows the surgeon to have the freedom of a laser cutting tool in his or her hand. The Omni Guide Beam Path has proven useful in the surgery of both benign and malignant lesions.59

Awake office based laser surgery is gaining popularity in the treatment of benign laryngeal lesions because of the relative safety of lasers and the quick recovery period post procedure. Though the CO₂ laser has traditionally been the laser of choice for laryngeal surgery, different lasers have been reported to be useful in office-based surgery. In the office, new technologies such as distal chip endoscopy and rare-earth doped fiber lasers have allowed for creative and innovative surgical techniques. Typical diseases treated with these new techniques are dysplasias and papillomas. A 585 nm pulsed dye laser was originally the laser of choice for vascular lesions; however the 532 nm pulsed KTP laser has proven to be superior. The use of the 2,013 nm Thulium laser which mimics the CO₂ laser closely may become useful as an office based laser as well.60–64 Even though otolaryngologists are performing more office procedures that incorporate lasers, the breadth of procedures remains limited for important reasons such as airway compromise, which is poorly handled in the office setting.

Pre-operative management of patients undergoing laser assisted otologic surgery includes a full history and physical, an audiogram and likely non-contrast computer tomography (CT) imaging of the temporal bone and internal auditory canal. When choosing a laser to use near a neurosensory organ like the ear, it is important to consider the potential collateral damage. The thermal and photoacoustic effects in laser use are a function of dosimetry and tissue optical and thermal properties. Bone has substantially smaller water content than skin or other soft tissues and visible wavelengths are not well absorbed. In the absence of any distinct chromophore, using an argon or a KTP(Nd:YAG) laser to ablate bone requires the use of an initiator. An initiator absorbs laser light and undergoes pyrolysis. In middle ear surgery, a small droplet of blood or charred tissue placed on the laser target serves this purpose. Accordingly, there is a risk of thermal injury, as considerable temperature elevations occur within this region, and ablation occurs with at best modest thermal confinement.82 In contrast, infrared wavelengths are well absorbed by both the hydroxyapatite crystals in bone and the interwoven collagen fibers. Ablation proceeds by the classical mechanisms just as in skin, though photoacoustic transients may be generated leading to audible pops. These mechanical transients may propagate through the inner ear and may result in injury to the delicate neuroepithelium.

In general, shorter laser pulse durations lead to less thermal injury provided the conditions for thermal confinement are met.94,95 However, repeated pulses in rapid succession may lead to the build up of heat in the target site; hence successive pulses should be separated by a sufficient amount of time to allow for complete thermal relaxation. Short pulse laser systems (e.g., Erbium:YAG) generate an acoustic pressure wave that leads to a vibration of the ossicular chain which may result in “noise trauma”. The heat generated by the laser may also cause “convection currents” that also lead to vibratory stimulations. Both of these stimulations can cause acoustic injury and should be controlled by appropriate dosimetry selection. Regardless, the mechanical transients produced during laser ablation are comparable or even less harmful than the vibratory effects produced using conventional methods to perform surgery.7,65,82,96,97

In addition to the argon laser, the CO₂ laser, the KTP laser and more recently, the erbium-YAG laser are used to perform a stapedectomy or stapedotomy in patients with otosclerosis. In the stapedectomy and stapedotomy, the stapedial tendon is vaporized with the laser, then the incudostapedial joint is disarticulated using mechanical instrumentation, and the posterior crus is severed with the laser (Fig. 11a, b). The anterior crus of the stapes is then fractured manually without the laser and the stapes superstructure is removed. The laser is then used to place a single large hole or a set of smaller holes generating a “rosette” type pattern in the stapes footplate to accommodate the prosthesis (Fig. 11c). A mobile prosthesis is put into place.65,68,70–83 No study to date has demonstrated which laser among the three most commonly used in stapes surgery (argon, KTP and CO₂) is best. Recently, erbium:YAG lasers have been developed for use in performing this operation, however the high cost of these lasers has limited broad adoption.71,98 The success of laser stapes surgery is based on audiometric analysis (hearing tests) and complication rates. Audiometric results after laser stapedotomy in relation to mean differences in the bone conduction auditory thresholds show improvements of 0.53–5.6 dB in those thresholds regardless of the laser system utilized.70,99

Smaller cholesteatomas and residual tissue in previously attempted excisions of cholesteatoma have been vaporized with the CO₂, Argon and KTP lasers with some reports of lower recurrence rates.65 Laser use is particularly beneficial when removing cholesteatoma from the delicate bones of the middle ear such as the stapes or in removing disease that traverses the obturator foramen of the stapes. When using the laser in this application, its energy is absorbed more by the cholesteatoma than by the bony surroundings.92,93