Laser Revision Stapedectomy

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Chapter 24 Laser Revision Stapedectomy

Larry B. Lundy

Videos corresponding to this chapter are available online at www.expertconsult.com.

In recent years, the safety and efficacy of revision stapedectomy have come under scrutiny. Experienced surgeons report that the results of revision stapedectomy are often worse than results of primary stapedectomy, and that the risks of sensorineural hearing loss, tinnitus, and vertigo are increased. With the application of laser technology to revision stapes surgery, less traumatic and more precise techniques can be applied, allowing better results and diminished risks compared with revision stapedectomy without lasers. This chapter reviews the clinically relevant principles of laser technology, compares results of revision stapedectomy with and without laser application, defines candidates for surgery, and reviews surgical technique.

LASER PHYSICS AND PRINCIPLES

Laser energy is derived from the release of energy (photons) occurring when stimulated electrons return to their resting orbital. As proposed by Einstein in 1917, when photons of the appropriate wavelength strike excited atoms, a second additional photon is released as the electron returns to its ground state (Fig. 24-1). In this stimulated emission situation, the photon that is emitted from the excited atom has exactly the same frequency, direction, and phase as the incident photon, providing laser energy that is collimated, coherent, and monochromatic.

FIGURE 24-1 According to the Bohr atomic model, an electron can absorb a photon, and the electron makes a transition to a higher energy level from its normal ground state. The electron eventually returns to the ground state by the spontaneous emission of a photon. In the condition of stimulated emission, a photon of appropriate energy interacts with the electron already in its excited state, causing the release of two photons.

(From Weisberger EC: Lasers in Head and Neck Surgery. New York, Igaku-Shoin, 1991.)

Lasers are typically named by the active medium, or the source of atoms that are excited and undergo stimulated emission of photons. The active medium can be a liquid, solid, or gas. Common gas lasers include CO₂, argon, and helium-neon. An example of solid state lasers are the neodymium:yttrium-aluminum-garnet (Nd:YAG) and the potassium titanyl phosphate crystal (KTP). The KTP laser is simply a Nd:YAG laser beam that passes through a KTP crystal, which halves the wavelength and doubles the frequency of the laser beam (Table 24-1).

TABLE 24-1 Characteristics of Laser Types

The wavelength of the emitted photons, or laser beam, has important characteristics for tissue interaction. Lasers whose wavelengths fall into visible (380 to 700 nm) and infrared (700 nm to 1 mm) portions of the electromagnetic spectrum are considered thermal lasers. Interaction of these lasers with normal biologic materials is mediated by a photothermal process. On contact with tissue, the laser energy is converted to thermal energy, resulting in a rapid increase in tissue temperature. The laser-tissue interaction depends as much on the tissue type and its composition (e.g., bone, muscle, cartilage, or nerve) as it does on the laser energy.

Visible-spectrum laser (argon at 514.5 nm and KTP at 532 nm wavelengths) energy absorption by tissue depends partly on tissue color. For soft tissue work, chromophores of hemoglobin and melanin absorb most of the energy. Lighter color tissues reflect most of the laser energy. Energy absorption from the invisible CO₂ laser (10,600 nm wavelength) is primarily by intracellular and extracellular water, which is instantaneously converted to steam.

For any laser, the magnitude of the laser-tissue interaction can be regulated by the laser’s power output, the power density at the point of impact, and the energy fluence. Every surgeon who uses a laser should thoroughly understand these fundamental concepts. Power is the time rate at which energy is emitted, and is expressed as watts. The power output is directly adjusted by the control panel on the laser console. Laser energy is delivered through a focusing lens. Power density is a measure of the intensity, or concentration, of the laser beam spot size (Fig. 24-2). It is the ratio of power to surface area of the spot size, and is expressed in terms of watts per square centimeter:

FIGURE 24-2 Planes of focus with spot size and power density.

where area of spot size is πr², and where r = spot size radius in centimeters.

Power density is inversely proportional to the square of the radius of the spot size. Consequently, for any specific power output, changes in the spot size can have a tremendous effect on power density (Fig. 24-3).

FIGURE 24-3 Relationship between spot size and power density.

The third fundamental, practical concept is that of fluence, which is simply the power density × time, expressed in joules (J). This is the total amount of energy delivered to the tissues:

As fluence increases, the volume of affected tissue also increases. The thermal energy having an impact on tissue increases dramatically as the time of exposure increases. If power density (W/cm²) is held constant, and exposure time is doubled, the energy delivered is doubled. The thermal effect of the tissue increases significantly, however, because the increase in temperature is continuous. For example, assume the laser power is set at 2 W, the spot size is 0.2 mm², and exposure time is 0.2 second. Is this the same as delivering two separate impulses at 0.1 second each? Yes and no. Yes, it is the same in terms of energy delivered from the laser. But no, it is not the same in terms of thermal energy imparted to the tissue because during the time between the two separate 0.1 second pulses, no matter how brief, the tissue is cooling (Fig. 24-4). Other factors come into play, such as the absorption characteristics of the damaged tissue in the center of the laser spot and dissipation of heat, but the important concept is that of the increase and decrease of the temperature.

FIGURE 24-4 A and B, Temperature and time of exposure relationship for a single pulse (A) versus two separate pulses (B).

HISTORY OF REVISION STAPEDECTOMY

Background

After the introduction of the stapedectomy procedure by Shea ¹ in 1958, the surgical treatment of otosclerosis was revolutionized. During the 1960s and 1970s, otologic surgeons performed hundreds of thousands of stapedectomies. An otologic surgeon commonly performed thousands of stapes procedures during his or her peak professional years. The accepted success rate (as defined by closure of the air-bone gap to ≤10 dB) was 90% or greater, with a 1% or less incidence of significant sensorineural hearing loss, including deafness. The most common technique during this time was the total stapedectomy, with removal of the entire stapes footplate. The small fenestra technique began gaining some acceptance, although not universal, in the early 1980s.

As with any surgical procedure, the success rate of stapedectomy was not 100%; with even a small percentage of failures (i.e., air-bone gap closure of >10 dB) in such a large pool of patients, there was a significant number of patients who were candidates for revision stapes procedures. Stapes surgeons soon discovered two important facts: The success rate of revision stapedectomy was not nearly as high as that of primary stapedectomy, and the incidence of significant sensorineural hearing loss, including dead ears, was significantly higher than the incidence associated with primary stapedectomy. Prominent otologists obtained air-bone gap closure within 10 dB in 50% or less of revision cases.²^–⁷ The incidence of significant postoperative sensorineural hearing loss ranged from 3% to 20%, with 14% having profound loss.^2,^3,^6,⁸

Glasscock ² and Sheehy³ and their associates and Lippy and Schuring^8,⁹ advocated leaving the oval window neomembrane intact and undisturbed, if possible, in revision cases to reduce the risk of severe sensorineural hearing loss, even though it may result in fewer patients with postoperative hearing improvement. Feldman and Schuknecht,⁴ Pearman and Dawes,¹⁰ and Derlacki⁵ reported opening the neomembrane to identify the vestibule and ensure correct prosthesis placement.

To diminish the risk of significant sensorineural hearing loss, the surgeon often would not open the oval window and vestibule, and would place a prosthesis on the existing oval window membrane. By doing so, the prosthesis would often rest on a thick fibrous oval window membrane or perhaps a residual bony footplate or new bone growth. Although this technique protected against sensorineural hearing loss, the lower incidence of closure of the air-bone gap to within 10 dB remained. The stark contrast of results of revision stapedectomy compared with primary stapedectomy, plus technologic advances in hearing aids, diminished the enthusiasm for revision stapes surgery in all but the most experienced hands.

Laser

Concomitant with the realization that revision stapedectomy surgery was not as successful as primary stapedectomy was the introduction of lasers in temporal bone surgery. The use of the laser in temporal bone surgery was the object of experiments in 1967 by Sataloff ¹¹ and 1972 by Stahle and colleagues.¹² The evolution of laser otologic surgery has been based on a mixture of clinical, experimental animal, and laboratory observations. In 1977, Wilpizeski¹³ examined argon and CO₂ lasers on monkeys by performing myringotomy, ossicular amputation, stapes fenestrations, lysis of stapedial tendon, and crurotomy. He noted damage to the organ of Corti in monkeys after using “excessive power.”

Escudero and associates ¹⁴ were the first to use a laser in human otologic surgery in 1977. They used the argon laser with a fiberoptic handpiece to tack temporalis fascia to tympanic membrane perforations. In 1979, Perkins¹⁵ presented a preliminary report of argon laser stapedotomy with excellent initial results in 11 patients. In 1980, DiBartolomeo and Ellis¹⁶ expanded argon laser applications in 30 patients for middle ear and external ear soft tissue and bony problems. In 10 patients, otosclerosis was corrected, including one revision case. In 1983, McGee¹⁷ reported on the use of argon laser in more than 500 otologic cases, 100 of which were primary stapedectomies. There were no laser-related complications in his study. In 1989, McGee¹⁸ reported an update on 2500 tympanomastoid procedures, of which 510 were primary stapedectomies. By comparing 100 consecutive laser stapedectomies with a previous 139 small fenestra stapedectomies using instruments, McGee found that the laser technique permitted much shorter hospital stay, less vertigo, and excellent hearing results (93% air-bone gap closure ≤10 dB at 6 months). This large study indicated the safety of argon laser use for stapedectomy, and yielded comparable hearing results and less vertigo. This clinical evidence is inconsistent with experimental animal studies, in which temporary changes of cochlear microphonics and saccular perforations were noted.^17,^19,²⁰ Clinical experience from several centers has illustrated the safe use of lasers in ear surgery; however, arguments and opinions persist regarding the best type of laser.²¹^–²⁵

Comparison of Lasers

The visible spectrum lasers were used initially because they were the only ones that were precise and accurate enough for stapes surgery. Similar to any tool or instrument, each type of laser has advantages and disadvantages. The visible-wavelength lasers (argon and KTP) have the practical advantage of precision because the aiming beam and the working beam are the same. The blue-green (argon) or green (KTP) aiming beam has clear, crisp margins, which allows extreme precision. Several years ago, some manufacturers of the KTP laser incorporated the use of a separate helium-neon laser aiming beam. This helium-neon aiming beam produces a red spot, and the margins are not as clear and crisp as the blue-green argon laser or green KTP laser. The alignment of the two beams (the helium-neon aiming beam and the visible laser beam) remains very precise because the wavelengths are similar (helium-neon is 632.8 nm wavelength).

The CO₂ laser beam is invisible; a separate laser aiming beam (helium-neon) is required. This aiming beam is coaxial and focuses in a different plane from the CO₂ laser beam because of the differences in wavelength of the helium-neon and CO₂ lasers. With these lasers, there is more potential for misalignment and a greater margin of error than with the KTP and argon lasers. It is crucial that the CO₂ laser and its helium-neon aiming beam be calibrated precisely and checked frequently during the procedure to ensure maximum accuracy.

The tissue absorption of the visible-laser energy is color dependent, and for the argon and KTP lasers, peak absorption is dark red. For lightly colored tissues, such as a neomembrane or bone, a significant amount of laser energy is reflected rather than absorbed. A practical solution involves placing a minute quantity of blood in the field, or applying several bursts (not in rapid succession) to get a dark char, increasing the laser energy absorption. With the CO₂ laser, this absorption is not a problem because the laser beam is invisible, and absorption by water and tissue is not color dependent.

The visible-wavelength laser beam can be carried by thin fiberoptic cables, which allow two modes of delivery: a micromanipulator attached to the microscope or a hand-held probe (Fig. 24-5). The hand-held probe provides greater angle of divergence of the laser beam (i.e., rapid deterioration of power density) and must be placed very close to the tissue. This instrument is directly in the operative field and can obstruct a portion of the visual operative field. With the micromanipulator, the angle of the laser beam is less divergent. It does not require an instrument in the field (except a suction for smoke plume removal), but does require the use of a “joystick” control mechanism to direct the beam. The CO₂ laser energy cannot be carried by a standard fiberoptic cable; use of a micromanipulator system is the only choice. Older CO₂ lasers have a system of articulated arms and mirrors that significantly reduces accuracy. Newer models allow the optical chamber to be attached to the side of the microscope, however, with fewer arms and mirrors, a significant technologic advance.

FIGURE 24-5 A, Micromanipulator delivery system. B, Hand-piece delivery system.

The delivery of CO₂ laser energy has potentially advanced with the introduction of an omnidirectional photonic bandgap reflector system developed by researchers at Massachusetts Institute of Technology in 1998. This technology allows for the CO₂ laser beam to be transported within a hollow-core, flexible fiber, eliminating the need for articulating arms and mirrors.²⁶ A commercial organization (OmniGuide, Inc.) was established in 2004, and the first otology device, OtoBeam, was used in June 2007. This optical fiber has an outer diameter of 0.9 mm, with a spot size of 0.25 mm. The angle of divergence when the CO₂ beam leaves the end of the optical fiber is 7 degrees; the tip of the optical fiber must be relatively close to the tissue to avoid significant power loss.

In recent years, questions have arisen regarding the safety of visible-spectrum lasers in stapedectomy and revision stapedectomy. The issue revolves around depth of penetration of laser energy into an open vestibule with potential injury to inner ear structures, such as the saccule or utricle. No laser surgeon advocates firing any type of laser beam into an open vestibule. These concerns have not been borne out, as experience with hundreds of patients and multiple authors has indicated.^15,^16,²¹^–²³ ^,25 ^,27

Serious theoretical safety issues related to visible spectrum lasers arose when Lesinski ²³ pointed out that the shorter wavelength of the visible wavelength (argon and KTP) lasers penetrates tissue more deeply than the longer wavelength (CO₂) lasers. By constructing a model of the vestibule and placing a black painted thermocouple in it at a depth comparable to the saccule or utricle, he measured very high temperatures when the visible laser was allowed to strike the thermocouple directly. This effect was not noticeable with the CO₂ laser. He concluded there was the potential for the visible lasers to traumatize the saccule or the utricle or both, risking sensorineural hearing loss.

Years of clinical experience with visible lasers used for primary and revision stapes surgery had failed to show clinical evidence to support this concept. This discrepancy between theoretical and clinical experience is probably best explained by the fact that visible laser energy is maximally absorbed by darkly colored or pigmented structures. A thermocouple painted black would absorb most of the laser energy of the KTP (green) and the argon (blue-green) laser. In the human inner ear, there are no darkly colored structures, however. The saccule and the utricle are a light pink; the laser energy is much more likely to be reflected rather than absorbed. A second possible reason that clinical experience fails to support the theoretical concern is the possibility that microperforations of the saccule or utricle or both do occur, but may have no clinical significance or measurable effect on hearing.

Laser Use: 1990s to 2007

The renewed interest in laser use for revision stapes surgery combined with the theoretical issues of “best” type of laser (visible versus invisible) sparked a series of self-appraisals by stapes surgeons. The two major concerns of revision stapes surgery—successful outcome (air-bone gap ≤10 dB) versus sensorineural hearing loss—continue to be important, regardless of use of the laser or not. In essence, revision stapes surgery has improved as surgeons have employed better selection criteria. A recurring theme throughout the literature is that patient selection for revision stapes affects the outcome. If a patient never had a good result to begin with, the chances are less that a good result would be obtained by revision. Likewise, patients with vertigo and reaccumulation of the air-bone gap do not fare as well. The results of revision stapes surgery without the laser are better than historical controls of the 1970s and 1980s (Table 24-2).²⁸^–³⁴ The results of revision stapes surgery using the laser are also better than the historical controls, and show a lesser incidence of sensorineural hearing loss (Table 24-3).^23,^27,³⁵^–⁴⁰

TABLE 24-2 Revision Stapes Procedure without Laser (1990s-2007)

TABLE 24-3 Revision Stapes Procedure with Laser (1990s-2007)

Analysis of Failed Stapes Surgery

The analysis of the long-term success and failure rate of primary stapes surgery is difficult for several reasons. The original surgeon seldom has the opportunity to follow all of the patients over the long term; the surgeon would be unaware of some of the failures. Most of the revision stapes surgery performed is often done by another surgeon other than the original. In our mobile society, patients often move to other locations. If their original successful result deteriorates, they may simply seek a hearing aid. Younger and middle-aged patients may outlive the older experienced surgeon, or at least live longer than the surgeon’s active practicing years. Finally, it is common that the original operative reports and audiograms are unavailable years later when the revision stapes is being considered. Although these circumstances are not unique to otosclerosis and otology, they increase the difficulty of establishing the long-term outcome of stapes surgery and of comparing different techniques, prostheses, and surgeons’ outcomes.

Nonetheless, several factors responsible for the reaccumulation of the air-bone gap have been repeatedly identified in almost all studies. The most common intraoperative finding associated with recurrence of conductive hearing loss is a displaced prosthesis.^29,^44,⁴⁵ Findings at the time of revision stapes surgery generally can be classified as common or uncommon (Table 24-4).

TABLE 24-4 Findings at the Time of Revision Stapes Surgery

Common	Uncommon
Displaced prosthesis	Dislocated incus
Incus erosion	Prosthesis too long
Fibrosis of oval window	Fixation of malleus/incus
New bone growth	Depressed footplate fragment
Prosthesis too short	Reparative granuloma
Residual footplate	Perilymph fistula

Although there are no excellent long-term follow-up data to support or implicate any one technique because of the previously mentioned social factors, certain conclusions can still be reached. Most of the primary stapes surgery involved total or near-total removal of the footplate during the years of frequent stapes surgery. Regardless of the prosthesis used, the oval window tissue seal is much larger than the prosthesis. All of the soft tissue seals (lobule fat, areolar fascia, temporalis fascia, vein, tragal perichondrium) have to occlude the oval window to prevent perilymph leak. Subsequently, a snug fit of this tissue results in prolapse of the tissue into the vestibule to some degree, or a relative heaping up of the tissue in the oval window niche, or both. As this tissue heals, portions within the vestibule could easily band to the saccule or utricle ^41,⁴² because the vestibule is only a few millimeters deep. When this tissue in the oval window is removed mechanically during revision surgery, tears and avulsions of the saccule or utricle or both could easily occur, resulting in vertigo or significant sensorineural hearing loss, or both. This potential for inner ear damage can be estimated only because there is no good way to assess this possible condition preoperatively or intraoperatively.

Accurate centering of the prosthesis in the oval window with these tissue grafts and total footplate removal is difficult because the margins of the oval window are obscured by the tissue grafts. As healing occurs, this tissue fibroses and matures, presumably resulting in scar contracture, which causes the distal end of the prosthesis to migrate to the margin of the oval window, where it adheres to the bony margin of the oval window. Subsequently, the combination of this adhesion/fixation and the inefficient angle of vibration of the prosthesis results in a conductive hearing loss from fixation. With stapedotomy or small fenestra techniques, this is a much less frequently encountered cause of failure because the prosthesis has much less tendency to migrate within the oval window.

With total or near-total footplate removal using mechanical techniques, footplate fragments can be left in the oval window or depressed into the vestibule. These fragments may be under-recognized because the purpose of revision stapes surgery is to re-establish an efficient conductive mechanism, not the total exploration of the oval window. These bone fragments, if contacting the prosthesis, impede the motion of the prosthesis, resulting in a conductive hearing loss. Bone fragments can be embedded in the soft tissue scar and be in contact with the saccule or the utricle or both. The removal of the scar tissue with mechanical techniques can concomitantly remove the embedded bone fragment and tear the membranous structures in the vestibule. There is no certain way to assess this possible condition preoperatively or intraoperatively.

Incus erosion at the lenticular process at the attachment of the prosthesis is another common finding in revision cases.⁴³^–⁴⁶ One theory of causation holds that a tightly crimped shepherd’s crook results in ischemia and subsequent necrosis of the lenticular process.^7,^47,⁴⁸ Another theory holds that a poorly performed crimping initially or owing to the “spring-back” nature of stainless steel used in the shepherd’s crook results in a loose-fitting shepherd’s crook.⁴⁹ This laxity results in differential vibration of the incus and wire, ultimately eroding a notch in the lenticular process. Several prostheses are available with platinum ribbons for the shepherd’s crook, supposedly for easier and better fitting crimping. Also, as noted earlier, migration of the distal end of the prosthesis, particularly with previous total stapedectomy, can result in fixation of the distal end of the prosthesis. Subsequent normal vibration of the incus within the prosthesis crook or bucket handle would likely result in erosion of the incus at its attachment. The appearance of the lenticular process is that it has been “sawn” through from repeated vibration.

Uncommon findings, such as a subluxated incus, previously unrecognized malleus/incus fixation, and improper prosthesis length, are avoidable causes of failure with proper training and clinical experience. Bony regrowth in the oval window owing to otosclerosis is a condition without a proven prevention strategy.

Case for Use of Lasers in Revision Stapes Surgery

During the 1990s through 2007, several studies analyzed the success and complication rates of laser revision stapes surgery (see Table 24-3). The results are consistent regardless of the type of laser used or the method of delivery of the laser energy. The average success rate in closing the air-bone gap to within 10 dB is 65%; the incidence of significant sensorineural hearing loss is 1.6%, and the incidence of dead ears is 0.3%. There is no significant difference in outcomes using the visible spectrum or CO₂ laser. Although these results do not equal the results of primary stapes surgery, they do represent an improvement of the historical controls.

How could the laser account for some of this improvement, particularly when there has also been an improvement in the results of revision stapes surgery without the use of lasers? The answer lies in the management of the underlying cause of the original failure. Lasers give the surgeon an additional resource with which to deal with unforeseen or difficult circumstances.

Proponents of use of the laser in revision stapes surgery maintain it is less traumatic and more precise than mechanical instruments. Laser energy in the soft tissue of the oval window results in less bleeding than with instrumentation, which improves visualization. Laser “hits” vaporize soft tissue, allowing for precise delineation of the margin of the oval window, identification of the prosthesis–soft tissue interface, recognition of regrowth of bone and existing bone fragments, and precise sizing of the fenestra. If a bony fragment is identified within the fibrous tissue of the oval window in the ideal site of planned prosthesis placement, it can be vaporized without having to manipulate it with instruments. Even with otosclerotic bony regrowth in the oval window, the laser can be used to create the fenestra and avoid the microdrill or pick. This ability to manage the oval window with less trauma partly accounts for the improved success rates and the decreased rate of sensorineural hearing loss.

Limitations of Lasers

A primary limitation of lasers is the learning curve associated with the micromanipulator or the fiberoptic handpiece. Visible lasers have both options, whereas the CO₂ laser uses the micromanipulator only, owing to the physics of the long wavelength of CO₂ and fiberoptic cables.

The potential for buildup of thermal energy in the oval window tissue is real; the rapid-fire sequence of laser hits should be avoided. Experienced laser surgeons recommend a 2 second pause between hits to allow for adequate tissue cooling. Evacuation of the smoke plume with a small suction also dissipates heat from this area by providing regional airflow around the oval window. No laser surgeon advocates allowing laser energy delivery directly into an open vestibule, regardless of the laser type; the precision of contemporary lasers permits one to avoid this.

The laser can also be useful in managing the incus because it can be used to vaporize the necrotic tip of the lenticular process. A prosthesis using nitinol for the shepherd’s crook has been introduced for primary stapes surgery.⁵⁰ Nitinol is an alloy with shape memory made of nickel (55.3% by weight) and titanium (44.7% by weight).⁵¹ The shepherd’s crook “shrink wraps” around the incus or malleus with the introduction of heat at 45° C (113° F). This heat can easily be obtained with a single KTP laser shot at 0.5 W at 0.1 second duration or use of a battery-powered cautery unit (eye cautery). Current published literature is limited to primary stapedotomy with this prosthesis,⁵⁰^–⁵⁴ but the author has used it on revision cases successfully with its attachment to the incus and the malleus. The use of a stapes prosthesis with a nitinol self-crimping shepherd’s crook eliminates the need for manual crimping, greatly simplifying this step. When this prosthesis is used for malleus attachment, care must be taken not to place the heat source too close to the tympanic membrane because a perforation could result. With the KTP laser, this possibility is greatly reduced because of the ability to place the laser spot accurately on the shepherd’s crook.

TECHNIQUE

Primary or revision stapedectomies can be performed with the patient under local anesthesia with intravenous sedation or under a general anesthetic. For anesthesia with intravenous sedation, typically 50 to 100 μg of fentanyl citrate and 1 to 2 mg of midazolam are administered intravenously before the ear is prepared and draped. A short-acting barbiturate (50 to 100 mg of thiopental) is administered intravenously just before infiltration of the ear canal. This agent allows a brief somnolence, allowing painless infiltration of the local anesthetic. With a 27 gauge needle, 1% lidocaine (Xylocaine) with 1:15,000 dilution of epinephrine is administered to infiltrate the ear canal skin. Typically, only 0.3 to 0.5 mL of this solution is used. The high concentration of epinephrine is not necessary for adequacy of vasoconstriction, but is used for a more rapid onset of vasoconstriction. During the surgical procedure, if the patient is restless and seems inadequately sedated, additional medication can be given. Caution must be exercised because an impatient surgeon or an inexperienced anesthesiologist can overmedicate, which paradoxically increases restlessness and movement.

Surgeons performing stapes procedures in the past frequently avoided general anesthesia. Typically, the patient with general anesthesia would have an endotracheal tube, which is a very strong, noxious stimulus to the larynx and trachea. The anesthesiologist would have to give high doses of anesthetics to suppress coughing and bucking during surgery. During emergence from anesthesia and extubation, the patient would frequently buck, gag, and cough, however. There was concern by surgeons that transmitted pressure could dislodge the prosthesis or graft, resulting in a poor outcome. In addition, the anesthetic agents (especially narcotics) plus oval window manipulation would cause the patient to become nauseated, and retch or vomit in the recovery room and immediately postoperatively, also causing concern of a poor outcome.

Since 1996, the author has almost exclusively used general anesthesia employing a laryngeal mask anesthesia system. With general anesthesia, the patient is completely motionless. Local infiltration of the canal skin is with the same mixture noted earlier. With the use of laryngeal mask airway, the patient has no laryngeal or tracheal irritation and is able to breathe spontaneously on his or her own. Particularly, extubation is much smoother without coughing, retching, and bucking. Severe, active gastroesophageal reflux disease is a contraindication to the laryngeal mask anesthesia technique. Patients with mild to moderate gastroesophageal reflux are given a histamine blocker (e.g., ranitidine) and metoclopramide intravenously in the immediate preoperative period. At the conclusion of the case, the laryngeal mask airway is removed with the patient still under deep anesthesia to avoid coughing and retching. As mentioned, the author has used this technique since 1996, and all patients undergoing primary and revision stapes surgery are discharged home within a few hours after surgery is completed.

A transcanal tympanomeatal-stapedectomy flap is raised with the patient under local anesthesia with vasoconstriction and intravenous sedation. On entry into the middle ear, the cause of the conductive hearing loss is assessed (Fig. 24-6). The malleus and incus are inspected and gently palpated to rule out fixation. Any obstructing middle ear fibrous adhesions are lysed with the laser. The chorda tympani nerve, if present, is frequently adhered to the tympanomeatal flap and can be sharply dissected with the laser. At the appropriate setting, the obliterating tissue of the oval window surrounding the prosthesis is vaporized until the exact oval window margins and depth are identified. For the KTP laser, the spot size is 0.15 mm, the power setting is 1.2 to 1.4 W, and the pulse duration is 0.1 second. For the CO₂ laser on the superpulse mode, the spot size is also 0.15 mm, the power setting is 0.8 to 1 W, and the pulse duration is 0.1 second.

FIGURE 24-6 A, Elevation of tympanomeatal flap. B, Migrated prosthesis with oval window obliteration.

FIGURE 24-7. A, Dissection of distal stapes prosthesis. B, Loosening of prosthesis at the incus. C, Removal of prosthesis.

FIGURE 24-8. Opening of vestibule.

The attachment of the prosthesis at the incus is freed or loosened with a right angle hook. The prosthesis may be removed at this point or may require further lysis at its base (Fig. 24-7). A series of laser hits are applied to the oval window neomembrane in a nonoverlapping rosette pattern in the center of the oval window (Fig. 24-8). A minimum of 2 second intervals between bursts is necessary to minimize heat buildup of the neomembrane and perilymph. A 0.6 mm stapedotomy is created and is incomplete until the vestibule and clear perilymph are identified. The stapedotomy size is confirmed by use of a 0.4 mm and 0.7 mm McGee rasp. If the incus long process is satisfactory, a nitinol prosthesis with a fluoroplastic piston of 0.5 mm diameter is used. A length of 4.25 mm is used in 90% to 95% of cases. If the lenticular process is unsatisfactory, the same type of prosthesis is used from the malleus to the fenestra. The most commonly used length for this prosthesis is 4.50 to 4.75 mm. After laser crimping, the ossicular chain is gently palpated to ensure freedom of movement and appropriateness of prosthesis length. The oval window is sealed with areolar fascia. The tympanomeatal flap is returned to its anatomic position and secured with saline-moistened absorbable gelatin sponges or antibiotic ointment.