CHAPTER 109 Transoral Laser Microresection of Advanced Laryngeal Tumors

Michael L. Hinni, John R. Salassa, Bruce W. Pearson

• Transoral laser microsurgery (TLM) permits both small and large laryngeal tumors to be resected. The limits of resectability are based on access and functional consequences and not on extent or T stage.

• Piecemeal resection of cancer permits precise tumor mapping and may improve local control over traditional en bloc resections. It further permits larger tumors to be removed through endoscopes that could otherwise not accommodate the physical volume.

• TLM offers numerous functional advantages including fewer tracheostomies, no fistulas, earlier swallowing, and sensation.

• TLM can replace traditional conservation laryngeal operations.

• TLM can fit well into multimodality therapy strategies.

Terms and Definitions

Transoral laser microsurgery (TLM) is a surgical treatment strategy for primary cancers of the mouth, pharynx, and larynx. In TLM, the instrument of excision is a carbon dioxide (CO₂) laser beam, an operating microscope imparts the perspective, and the natural passageways of the upper aerodigestive system provide the access.

Two features distinguish TLM from open surgery ¹: healing is allowed to occur by secondary intention² and the tumor block can be subdivided into manageable units by the laser (in situ).

TLM is clearly a conservation strategy, but it is not a reconstructive one. “Piecemeal” removal is a distinguishing feature of TLM—and a key source of controversy. Tumor transection endows important diagnostic dimensions to TLM, and magnification exploits the difference in visual appearance between normal tissue and cancer.

Safe TLM requires two conditions: adequate exposure through the mouth and a tangible specimen.

TLM is an excision, not vaporization. A specimen is the basis of meaningful frozen section margins. Individual specimens may be small, but, in aggregate, the resected tissue volume parallels that of an open operation.

In many ways, TLM is a misleading name. Transoral laser microsurgery is not totally transoral—open surgery is still required for nodes in the neck. TLM is not entirely laser, either—it depends on endoscopic cautery, vascular clipping, and occasionally blunt and sharp dissection. Finally, TLM is not exclusively surgical—radiotherapy may be offered (for neck indications, but never to finesse margins).

The aim of TLM is to improve cure and function through patient selection and technical excellence. The goal is the cure rate of open surgery and the functional promise of a tissue-conserving treatment like radiotherapy, all of this with less morbidity, at lower cost.

“Advanced” (as in “advanced laryngeal tumors”) is a confusing term. In the context of laser surgery, it once meant any tumor larger than T1a glottic. In traditional discussions, it used to mean cancer with a fixed cord. The staging system suggests a different connotation—positive neck nodes. What is clear is that laryngeal cancer is not one disease. It is many different diseases. And unless we digress and clarify the descriptors of the different laryngeal cancers, all discussions of treatment are ambiguous. The answer to the question, “Does an advanced case qualify for TLM?” is “It depends. What do you mean by advanced?” Let’s look at the classifications.

Is it cancer? Laser surgery manages everything along the histologic spectrum, but this chapter only relates to the worst actor, invasive squamous cell carcinoma. The Ljubljana taxonomy ³ is probably the closest thing we have to an internationally accepted classification of epithelial hyperplastic laryngeal lesions (EHLL). For the most benign, “simple hyperplasia,” acanthosis predominates. “Abnormal hyperplasia” is next, and basal proliferation is the hallmark. “Atypical hyperplasia” features dysplasia and atypia. Fourth is carcinoma in situ (CIS), cytologic neoplasia on an intact basement membrane. All these can be laser resected, but TLM is a higher strategy for a higher challenge, group five, neoplasia with subepithelial penetration (i.e., invasive squamous cell cancer).

Is it TLM? An excellent classification for laser cordectomies has been developed by the European Laryngological Society.⁴ It names five types: subepithelial, subligamental, transmuscular, total, and extended cordectomy. The first three are elegant one-piece excisional biopsies, and a laser may be used on them. TLM (and the strategy of depth determination) comes into play for the last two.

What site? Before “multidisciplinary” committees imposed a theoretic anatomic classification (glottic, supraglottic, and subglottic) on laryngeal cancer, surgeons included clinical behavior in the sorting system. For 50 years, laryngeal cancer was “intrinsic” or “extrinsic.”⁵ Intrinsic was “interior region” cancer, primarily glottic in origin, and slow growing, and its nodes were generally late.⁶ TLM treats most of these, but not all. Extrinsic cancer was more supraglottic, originating around the laryngeal opening or its pharyngeal surface. It had a higher rate of metastases and was more lethal. TLM treats the local disease, but not the metastases.

Now the official categories are glottic, supraglottic, and subglottic, whereas “transglottic” is used to describe tumors that span the ventricle. However, in the anterior larynx, glottic and subglottic cancers behave similarly.⁷ Subglottic cancer often turns out to be glottic, with descent. The height of the glottis is controversial (5 mm high, 10 mm high), or excluded posteriorly (sparing the posterior commissure). None of the sites is off limits to TLM.

In discussing local extent, clinicians often reduce their spoken references to “early” and “advanced” laryngeal cancer, the traditional dividing line being vocal cord motion. In these terms, TLM is primarily an “early” cancer treatment, as opposed to the “advanced” group.

The tumor, node, metastasis (TNM) staging system ⁸ uses T_X, T_is, T₁ (a and b in the glottis), T₂, T₃, T_4a, and T_4b to define a local tumor, expanding 3 regions to 18 “extents.” And this is just for the local disease (T). Nodes multiply the possibilities by 7. Metastases multiply the possibilities by 3, for more than 300 possibilities. Some are suitable for TLM. Some are not. No one knows where we should place the dividing line, or where “advanced” should start (or end). The staging system does encourage a summary format, stage 1, stage 2, stage 3, and stage 4, but the neck dominates this classification. If the neck is positive, everything is stage 3 or 4 (advanced), even if the primary is miniscule.

The staging of laryngeal cancer is not linked to any particular therapy and has significant limitations. TNM staging leaves out historic factors (age, previous treatments, habits, work, duration of and number of symptoms, literacy, religious beliefs, distance from treatment facility, etc.) and leaves out comorbidities. Both symptom severity scores and comorbidity scales have been shown to improve the accuracy of TLM.⁹ TNM also ignores complex patient factors (e.g., exophytic vs. endophytic, keratinized vs. ulcerated, stridor, obesity vs. cachexia, forced expiratory volume, ejection fraction, hemoglobin, protein levels, blood sugar, liver function tests). These and other limitations of TNM staging pose challenges to the treating physician.

This leaves the doctor with the problem of how to interpret the term “advanced” in the context of TLM. It makes little sense to link advanced to a higher TNM stage (3 or 4) if patients with T₁ and T₂ local cancers will be included (all that is required to make a T2 cancer “stage 3” is for someone to feel a node in the neck). For example, the 2002 American Joint Committee on Cancer (AJCC) TNM staging of larynx cancer states that stage III includes T₁, T₂, or T₃ N₁(or T₃ N₀), where N₁ is a single node smaller than 3 cm. The AJCC also lists stage IVA to include T₁, T₂, T₃, or T_4a N₂ (or T_4a N₁ or N₂), where N_2a is a node between 3 and 6 cm in size, on the same side; N_2b is multiple nodes smaller than 6 cm, on the same side; and N_2c is bilateral or contralateral nodes smaller than 6 cm in size.

This chapter is primarily about the treatment of the local diseases by TLM. Therefore we need to classify local diseases and to help distinguish those for whom TLM is an option and those for whom it is not.

Five Types of Local Laryngeal Cancer

From the surgeon’s standpoint, local laryngeal cancer comes in five different “flavors,” each one more damaging (to function) and more difficult to cure. Severity relates to what stock local excision would be required for complete removal. What would that impose on the patient, in terms of voice, swallow, and nasal breathing? This does not indicate the treatment is surgery. It does ensure that the appropriate local option for surgery is identified, especially to the patient, when the selection among various modalities is made. Each flavor can thus be defined by one of five classic excisions, which ascend in severity from laryngoscopic biopsy to total laryngectomy. Each excision removes a customary block, from one nodule to the whole larynx and its coverings, and each has a formal technique. We have a published record for each of local control rates from 98% to 80%. The expected functional outcome ranges from normal voice, swallow, and breathing down to tracheoesophageal puncture (TEP) voice and stomal breathing. Each of these five categories can be named as follows: very early, early, intermediate, advanced, and very advanced.

1. Very Early

Exophytic midcordal T_1a carcinoma. Encompassed by transoral excisional biopsy removal. Includes one-piece subepithelial cordectomy (stripping), subligamental ⁴ partial cordectomy, and midcordal transmuscular cordectomy.

2. Early

Two subtypes, glottic and supraglottic.

a. Early Glottic

T_1a, T_1b, and T_2a true cord carcinoma whose formal external excision would be a vertical partial laryngectomy,^10,¹¹ or hemilaryngectomy.^12,¹³ The European Laryngological Society’s total cordectomy and extended cordectomy¹⁰ concepts probably fit here.

b. Early Supraglottic

T1 supraglottic carcinoma fitting within a supraglottic laryngectomy block.^1,^14,¹⁵

3. Intermediate

Laryngeal cancer that fits within a supracricoid partial laryngectomy block.^16,¹⁷ Thus T₂ glottic carcinoma (T₂ by spread to the supraglottis), T₃ glottic (T₃ by thyroid cartilage erosion from the anterior commissure—mobility is preserved), T₂ supraglottic (T₂ by descent to involve the vocal cords), or T₃ supraglottic cancer (if T₃ by involvement of the preepiglottic space PES).¹⁸^–²⁰

4. Advanced

T₃ glottic carcinoma (T₃ by unilateral cord fixation and invasion of the paraglottic space or the thyroid ala) is the prototype because it is lateralized and fits within a near-total laryngectomy.²¹ Lateralized invasive T_2b glottic carcinoma qualifies if the T_2b is by impaired mobility of one vocal cord. Also, advanced glottic carcinoma includes T₂ supraglottic carcinoma, where T₂ means involvement of the vallecula or the medial pyriform wall, and T₃ supraglottic carcinoma, where T₃ means unilateral cord fixation with invasion of the paraglottic space or the thyroid ala.

5. Very Advanced

Bilateral anterior T₃ glottic carcinoma invading both ventricles, bilateral posterior T₃ supraglottic cancer invading the postcricoid region, or T_4a glottic or supraglottic carcinoma, which means the cancer has invaded into adjacent structures outside the larynx—the strap muscles, the thyroid gland, the tongue beyond the immediate base, the trachea, or the esophagus. The minimum excision these cancers would require is at least a wide field total laryngectomy (T_4b is incurable by surgery). T_4b means gross distant extension. But this is virtually unheard of in cancers with no prior treatment. Examples include direct extension into the prevertebral space or the mediastinal structures or encasing the carotid.

Now we can examine TLM in the context of the clinical severity of the local disease. Others can judge the use and validity of the approximate term locally advanced.

Acronyms

CHEP Cricohyoidoepiglottopexy.²² Reconstruction for supracricoid partial laryngectomy (SCPL).

CHP Cricohyoidopexy.^23,²⁴ Reconstruction for SCPL.

HSL Horizontal supraglottic laryngectomy.

NTL Near-total laryngectomy.^25,²⁶ Frontoanterior VPL with epiglottoplasty, SCPL, and NTL have at various times all been called subtotal laryngectomies.²⁷^–³⁰

PES Preepiglottic space.

SCPL Supracricoid partial laryngectomy. Frontoanterior VPL with epiglottoplasty, SCPL, and NTL have at various times all been called subtotal laryngectomies.²⁷^–²⁹

TLM Transoral laser microsurgery.

TEP Tracheoesophageal puncture, tracheoesophageal prosthesis.^31,³²

VPL Vertical partial laryngectomy. Includes the vertical frontoanterior and frontolateral ^10,^11,^33,³⁴ partial laryngectomies, and hemilaryngectomy.

Laser Surgery and Transoral Laser Microsurgery in the Treatment of Early, Intermediate, and Advanced Cancers

Laser surgery is not new in larynx cancer. Davis and colleagues ³⁵; Jako and colleagues³⁶; Strong³⁷; and Vaughan and assessites³⁸ all treated selected tumors during the 1970s and early 1980s.

Through the 1980s and 1990s, Motta and others ³⁹ and Steiner^40,⁴¹ pioneered a new concept: tumor transection in situ. Consider the implications. If infiltrative cancer could be safely resected in pieces, tumor depth could be determined in situ. Incremental resection would become possible—as in Mohs’ chemosurgery.⁴² (Mohs treated cancer successfully in more sites than just the skin.) One could “follow the tumor” (i.e., custom tailor the excision to each individual patient). If tumors could be subdivided into manageable subunits, early, intermediate, and even some advanced laryngeal cancers might be candidates.

Of course, transoral cordectomy provided outstanding results long before the laser was added. Suspension ⁴³^–⁴⁶ and the microscope were the keys, not a laser. What the laser added was questionable—costs for new equipment, time to set up, regulations in the operating room, thermal injury hazards, maintenance issues, anesthesia issues, more suction, filters, retraining requirements, and new credentialing. And what the laser gave up was considerable—the tactile feedback of cold steel microinstruments, the ability to cut around corners, the plume-free operating site, the char-free pathology specimen, operating room space, an unencumbered microscope, and the precision of a cut path versus a vaporization path.

But in the 1980s and 1990s, a sustained experience of endoscopic laser surgery for larger than T_1a glottic cancers was growing in Germany.^40,^41,⁴⁷^–⁵¹ This raised additional questions among traditionalists. They had concerns about exposure, hemostasis, reconstruction, margins, and wound healing. The greatest concern, however, was tumor transection. Steiner cut right through laryngeal cancer—in situ—through a laryngoscope! The claimed advantage was visualization and confirmation of tumor depth. How did the skeptics respond? First, they were asked to compromise access and work through smoke with an endoscope, with no convincing evidence this was meaningful. Then they were asked to give up orientation and violate the principle of en bloc resection—with no laboratory evidence this was safe!

Other concerns fueled the discussion. After a laser supraglottic resection, there was no reconstruction! Open supraglottic laryngectomy always led to aspiration if one failed to repair the gap between the glottic unit and the tongue base.^15,^52,⁵³ After laser SCPL, there was no cricohyoidopexy. Yet this was essential in open SCPL.^19,²⁴ There were so many additional issues a laser did not address (e.g., bleeders over 2 mm, ossified cartilage, neck nodes).

Furthermore, the obvious problems of access were troubling. Big tongues, small mandibles, capped teeth, mild trismus, and other challenges all lay in waiting, even for the most resourceful of operators. Very early midcordal T_1a carcinomas may have been fine. But early cancers would require greater exposure, intermediates more, and so on. Some would be too big to extract through an endoscope. A growing plethora of “laser laryngoscopes” raised suspicion that the problem of access remained unsolved.

Another challenge would be quality control from the pathology department. In cancer operations, negative margins are compulsory. If laser specimens were vaporized, the pathologist would have no margins to read. If they were excised with a laser, margins would at best be charred. If they were excised in several pieces, positive margins would be meaningless!

In North American practices, these considerations delayed TLM. This occurred despite much of the pioneering work originating in North America—the entire organ serial section studies from New Haven,⁵⁴ Philadelphia,⁵⁵ and Toronto^56,⁵⁷; the development of the CO₂ laser itself at American Optical Corporation by Strong⁵⁸ and associates in 1965; and the pioneering clinical laryngology of Strong³⁷; Jako,³⁶ Vaughan,³⁸ Davis,³⁵ and Ossoff⁵⁹ and their coworkers; and Shapshay.⁶⁰ But the German centers were leaders in the collaborative development of all the ancillary laryngologic instrumentation needed to capitalize on the technique. They pushed their experience well beyond the concerns recited earlier, tracked their results, and continue to report on their experience.⁴¹

In 1996 the authors of this chapter began to study this body of work more closely, and subsequently we took numerous steps to incorporate TLM into our practices. This effort provided new perspectives on laryngeal cancer management and the initial selection of therapy. Now we seek to share what we have learned.

Theoretic Basis of Transoral Laser Microsurgery

TLM does violate a time-honored dictum of surgical oncology—en bloc resection. A typical glottic or supraglottic cancer (above T₁) is likely to be extracted in three to six separate pieces!

En bloc has always been a prudent tactic to avoid unseen physical dispersion of viable malignant cells in a wound. When a scalpel penetrates cancer, the cells exposed will be alive. Viable cancer cells may adhere to the blade. Nothing prevents the surgeon from inadvertently transferring unseen cancer to an adjacent site in the wound. If unseen cell transplantation does occur during open surgery, and then we close the wound, how could tumor not recur? In open traditional surgery, this is why we isolate cancer in an unbroken package of normal surrounding tissue—to prevent contact between cancer and a scalpel or a scissor. This way, maybe we can avoid transplanting living malignant cells from the cancer back into the patient.

Rethinking this chain of events in laser microresections raises a new question. What would be the apparatus of physical transplantation? Cancer cells do not adhere to a beam of light. There is no physical carrier to transplant the tumor. Then again, grasping forceps and the suction cautery tips are used in TLM. They could do it. But assuming no tearing of the specimen, how would exposed cancer cells be viable? Cells revealed by laser energy are thermocoagulated, not viable. Finally, in the TLM paradigm, we do not close the wound. An unseen cancer cell falls on a thin layer of coagulum, not a healthy tissue surface. This layer is gradually sloughed, not incubated.

These are theoretic reasons we postulate that laser surgery permits local cancer ablation without en bloc resection. Is there any laboratory or clinical data? Werner and colleagues showed (for CO₂ laser incisions) that the lymphatic vessels of the wound margin are sealed immediately, and lymphatic vessels remain sealed for about 10 days after laser surgery.⁶¹ And we also have 20 years of European clinical data.⁶²^–⁶⁵ Steiner and colleagues^41,⁶⁴^–⁶⁷ have been performing TLM since the early 1980s. He and his colleagues have observed a low local recurrence rate (2% to 10%), a high survival rate, and a low rate of complications.^66,⁶⁷ They have not seen an increase in late neck or distant metastases during follow-up of more than 10 years. The incidence of cure by TLM is the same as the best results reported for open conservation surgery. Put another way, open surgery follows the principle of block resection but produces no more local cures than TLM! TLM allows laser tumor subdivision, but local failure occurs with the same low incidence as in traditional open conservation surgery.

If tumor transection can be safely accomplished (it is not automatic, care is still important), we have an attractive new technique to determine the depth of cancer invasion before we commit to the plane of excision. If we misjudge and cleave too close to the tumor, this is just another form of tumor transection. We can extend the excision, incrementally. All we have lost is some time.

If tumors can be divided in situ, the tumor itself ceases to be a factor in obstructing our vision. Complete removal always requires that we expose the entire mucosal margin of the tumor. Now we can achieve that goal in a mosaic of views, unrestricted by the bulk of the disease.

If tumors can be extracted in pieces, the internal diameter of the laryngoscope does not set the limit on how large a tumor we can resect. The limit becomes the exposure for each step and our disciplined attention to specimen orientation. Mohs ⁴² transected cancers in situ successfully, and his attention to orientation was uncompromising.

Later in this chapter we summarize our TLM results, as well as those of others.⁶⁷ We have documented a low incidence of failure at the primary site and also reported the ultimate causes of death. Our conclusion is that ultraradical treatment of the primary is not justifiable in a disease for which the main causes of death are advanced neck recurrences, distant metastases, second primaries, and serious general diseases. In modern times, quality of life is increasingly salient. In related diseases like hypopharyngeal cancer (TLM treats pyriform cancer, too⁶⁸), 5-year survival rates have stood between 15% and 30% for decades. Aggressive combined therapy (chemotherapy, radiotherapy, and radical surgery) have not improved the poor prognosis. Again, if we can effect local control with conservation laser surgery, the argument in favor of radical ablation clearly declines.

Transoral Laser Microsurgery Compared with Open Conservation Surgery

Open operations approach intralaryngeal carcinoma from its “blind side.” The surgeon cannot see the primary cancer until he or she has opened the neck, divided the fascia, separated the strap muscles, opened the framework, and penetrated the lumen at a critical point, determined by the local anatomy. Once exposed, field margins are oozy, not laser cut. Structures within the field relocate with the surgery, instead of maintaining a fixed position. The tumor margins are diminutive, not magnified, and the headlamp is illuminated, not microscope super-illuminated. For safety and reproducibility, open operations closely replicate a named excision block, chosen without the benefit of intraoperative depth information. For example, supraglottic laryngectomy removes the superstructures above the cords, which produces a predictable wound, requires a characteristic reconstruction, and can be repeated for numerous supraglottic cancer patients, despite the fact each has unique anatomy, distinctive preoperative findings, and slightly different tumor characteristics. Because the neck will be opened, the timing of a node dissection is determined. The neck dissection is continuous with the primary wound, so steps must be taken to prevent a fistula. Because the framework is elevated to the tongue base and both swell, airway safety demands a temporary tracheotomy. Supraglottic laryngectomy supports the principle of en bloc resection, but this was necessitated by the scalpel, not the cancer. It assists teaching, but for gross anatomy, not for the microanatomy and micropathology. Open supraglottic laryngectomy provides the access needed for reconstruction, but the open surgery necessitated the reconstruction.

By approaching laryngeal carcinoma through the mouth, TLM requires no disassembly for access. The laryngeal framework continues to support the airway. A tracheotomy is usually superfluous in a supraglottic TLM. The strap muscles retain their swallowing contribution. Through the endoscope, the operator confronts the authentic primary right from the beginning of the resection, with no disassembly of the patient just to reach the cancer. The laryngoscope stabilizes the field. The magnification and brilliant illumination unveil important subtleties (e.g., dysplasia at a margin). With no disturbance of the neck, and no connection of a neck wound with a laryngeal wound, pharyngocutaneous fistulae disappear from the list of potential complications.

During TLM, diagnosis continues.⁶⁹ Wherever the local tumor extends, the microscope and the laser try to follow. Magnified tissue appearances acquire new significance. Some tumors change the vascular patterns in the mucosa. Deeper in, invasive cancer tends to appear pale and dysmorphic. Tissues give up subtle information about their consistency as they are retracted. Cancer is stiff or soft (soft can progress to friability and bleeding). Beyond the tumor, the expected microarchitecture is striated muscle, fat, seromucinous glands, fibrous perichondrium, (ossified) cartilage, or bone. Fat looks yellow and lobulated; mucous glands are pale and lobulated but more noticeably vascular. Muscle is striated. Fibrous tissue is white and dry. Ossified cartilage and bone carbonize to a dominoes-like appearance. The undersurface of the strap muscles is loose and areolar.

TLM is a natural ally of combined treatment. Once the tumor is out, the locoregional microvasculature is still undisturbed—the best milieu for postoperative radiotherapy. And complete three-dimensional resection under the microscope has minimized the chances of a positive margin.

During the weeks after TLM, the endolaryngeal wound heals by secondary intention (in many ways similar to a tonsil bed). The framework resists stenosis because it remains intact. The thermal damage from laser resection is superficial (after electrocautery, it is deeper). No local flaps are mobilized or transposed, so there is no chance to bury residual tumor. “Second look” endoscopies become a meaningful way to revisit the primary site.

Months later, persistent granulation may signal the need for endoscopic removal, to improve voice. Follow-up laryngoscopy also allows the removal of small, ossified cartilage sequestra, which sometimes develop after laser resection has been carried down to the framework. Reepithelialization seems to forecast recovery but does not completely eliminate all risk of recurrence. Not even a negative second look excludes later recurrence. An overhanging anterior glottic scar may hide an unsuspected nubbin of residual tumor—still a salvageable circumstance, by simple laser resection, if discovered in time by this tactic. Before recommending TLM, discuss the willingness of the patient to return for a “second look.”

Instrumentation and Techniques of Transoral Laser Microsurgery

Instruments

We use a floor-model CO₂ laser console that can generate an output beam of 1 to 50 W or a hand-held hollow CO₂ fiber (Omni-Guide). The latter device permits some cutting at angles. Two modes, pulsed and continuous, are possible. Pulsed mode produces the fastest vaporization and the least adjacent thermal injury—the least char, hence the best clear recognition of the texture at the cut surface. But any vessel larger than an arteriole will bleed, and the bleeding must be arrested with electrocautery. Pulsed mode at low power (2-3 W) is ideal for glottic mucosa. One can maintain control over the cut (working slowly), avoid collateral heat (especially unintended thermal injury to the anterior commissure), and also avoid a “hole” of unintended depth (by pausing). For most normal laryngeal incisions, we use continuous mode at around 6 W of power. This setting provides excellent hemostasis but not enough char to upset the pathologists. Most mucosa bleeds too much in pulsed mode. Continuous mode results in a little more coagulation (about 50 to 100 µm).

The overall spectrum of power in laryngeal work is wide—1 W (focused, pulsed mode, for fine cutting of cordal mucosa), to 20 W (defocused, continuous mode, to vaporize friable semi necrotic centers inside bulky cancer, one of the few justifications for vaporization).

Besides mode and power, four more variables influence the effect:

• Speed: How quickly one moves the beam. Thermal transmission takes some time.

• Focus: Defocus the beam to create a superficial cautery effect but turn up the power, especially for broad forward advancement. Defocusing reduces the density of the power.

• Target tissue: Normal tissue (moist, not running wet) cuts best. Wet tissue (fluid is visible) cuts slowly, with a lot of thermal artifact from the boiling that has to take place first.

• Bleeding: Flowing blood stops laser surgery cold. It has to be ended (with electrocautery) before the excision can continue. Bleeding tissue just takes refuge under an expanding black char ball. Paradoxically, a beam set for the least char may impose the greatest char, by requiring the use of electrocautery.

An articulated arm brings the laser beam to the microscope body. From here we direct it with the joystick on a Sharplan Acuspot 712 micromanipulator. The frame of the micromanipulator bears a gimbaled half-silvered mirror through which we see the target and with which we manipulate the laser beam. The narrowness of the micromanipulator frame is important. Anything wider than the microscope body will conflict with the introduction of instruments (22 to 23 cm long). Unimpeded maneuvering and hemostasis at the primary site demand a clear path alongside the microscope for the grasping forceps and suction cautery tubes.

If the hollow Omni-Guide CO₂ fiber is preferred, the micromanipulator can be removed from the microscope granting greater visibility and increasing the working space. The company can provide both straight and angled introducing fiber carriers. Occasionally we use both the micromanipulator (for precise tremor-free work) and the fiber.

The CO₂ cutting beam is invisible, at 10,600 nm (far infrared). The wavelength of visible light is 400 nm (violet) to 700 nm (red). The surgeon observes a red spot on the target produced by an integral red Helium Neon (HeNe) beam at 632.8 nm (visible red). A video camera is mounted on the microscope as in otologic microsurgery. A monitor displays the operative field, so the operating room nurses can anticipate and assist.

More than anything else, laser microresection requires sophisticated skills in direct laryngoscopy. Much of this is experience, but part of it is an understanding of the laryngoscopes. Narrow tubular endoscopes (i.e., narrow side-to-side) overcome difficult exposure best. The tongue is incompressible (a fluid) and confined by the arch of the mandible. It can only be distorted. Wherever the scope contacts the tongue, it employs strong pressure and deforms it such that a straight path to the anterior commissure results. The narrower an endoscope, the more it can sink into the tongue, and the more the tongue can squeeze around the sides.

A narrow vertically oval instrument like the Hollinger anterior commissure laryngoscope is the optimal tool to overcome difficult anterior visualization. But a narrow monocular laryngoscope is too narrow to accommodate the side-by-side dual optical pathways of an operating microscope. A Dedo anterior commissure laryngoscope overcomes this limitation. It provides just barely enough width to accommodate a microscope. The Zeitels Endocraft laryngoscope ⁷⁰ maintains this advantage and adds a useful tip enhancement for glottic work—less bevel. A blunt tip is better for holding aside the false cords. Regular tips actually cover the anterior commissure by the time the rest of the barrel reaches distal enough to lateralize the false cords. Zeitels’ scope also features proximal slots along the sides to improve access for the instruments. Special modifications load both the Dedo and the Zeitels instruments with extra light and need extra suctions carriers. Laser plume is the most troublesome limitation to clear vision during TLM, so the optimum allocation of suctions is important.

Storz and colleagues ^66,⁶⁷ have developed a specific assortment of laryngoscopes for TLM. Their standard adult laser laryngoscope (8661 CN) has a dome-shaped cross-section, a lip at the tip (anterior commissure), and an unobtrusive suction channel incorporated into the upper wall of the blade and the handle. For larger tumors, distending laryngoscopes are the best. Two we have considered indispensable are the Weerda distending operating laryngoscope (8588 L) and the Weerda/Rudert distending supraglottiscope (8588 E). These instruments are wider, independently adjustable, and fitted with great suction tubes. The upper blade features flare at the side to help hold the tongue out of the way. The lower blade mounts on a strong left proximal C arch (8588 L) or a strong ring (8588 E) to provide minimal encroachment on instrument access.

The best vallecular laryngoscope is probably the Lindholm instrument (8587 A). The essential laser laryngoscopes for difficult access and subglottic access are the Steiner models. These are long and thin. The “half dome” subglottiscope (8661 DN) sinks into a large tongue the best, and the suction channel is incorporated into the handle. The flat-bodied subglottiscope (8661 E) gets past prominent incisor teeth the best, and a separate suction can be clipped.

We protect the incisors by fashioning a custom splint of heated Aquaplast (PS-1685), a thermoplastic substance that sets to a hard stable cap and diffuses the pressure over five or six teeth (WFR/Aquaplast Corp., Wyckoff, N.J.). Sometimes we provide external counterpressure to the larynx with a band of tape across the table to provide downward pressure to the larynx.

You can never have too much suction for plume evacuation—suction tubes on the laryngoscopes, suction tubes on the grasping instruments, suction in the insulated cautery, and plain dedicated suction tubes. Support each one with a separate suction line. Then add special suction tubes for blood. We prefer plain suction tubes for cleanup and gentle tissue manipulation and insulated suction-cautery tubes for flowing blood (two of each). Insulated (model 8606) suction cauteries come in various diameters—the insulation is necessary to prevent them from sparking out to the endoscope. Prevent suction trauma (and worse, sticking to a friable specimen and tearing it) with a small relief hole in the tubing or at the sucker tip. We recommend at least three separate suction lines per case.

Larger vessels sometimes require something more targeted than suction cautery. Insulated model 8663 alligator forceps will pick up a small bleeder around a corner for electrocoagulation. Control the lateral vascular pedicles coming into the supraglottis with insulated MicroFrance CE 0459 bipolar cautery-forceps (specify 22.5-cm length). Place titanium clips on named arteries such as the superior laryngeal and the anterior cricothyroid arteries. Delayed secondary hemorrhage would be a formidable complication in a patient with no tracheotomy. Stop this problem before it arises by using laryngeal vascular clip applicators (model 8665 works well).

Bouchayer fenestrated forceps (8662 R or L) are excellent grasping instruments for small cordal specimens. But to secure the grip we need on the larger specimens we manipulate in TLM, normal laryngeal microinstruments are too delicate. Saw-tooth grasping forceps meet the need. Use one (model 8662 EL, FL, GL, or HL) to maintain a stable grip on tumor subunits. Use two to advance by double grasping. The L denotes a suction channel.

Controlled resection is only as certain as the stability we create for the micromanipulator. A rock-steady microscope stand, like a Universal S3, serves our Zeiss OPMI 111 well. Reduce the wrist and finger movements you transmit to the system with adjustable armrest stabilizers on a pneumatic chair (like the Möller-Wedel Combisit E). Adjust the microscope and the patient to a comfortable position for you (as in otologic microsurgery) instead of the other way around.

During TLM, operating laryngoscopes require frequent redirection. This is why a rack-and-pinion chest table (like the Storz Göttingen model) is worthwhile. It permits efficient breakdown and redirection of the suspension system, which affords the operator the opportunity to quickly re-establish a different stable vantage point several times per case. Coupled with table-height and tilt adjustment (controlled from the head end of the table too), the operator can repeatedly re-establish the optimal line of sight.