Special Problems of Otosclerosis Surgery

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Chapter 25 Special Problems of Otosclerosis Surgery

William H. Lippy, Leonard P. Berenholz

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

As the incidence of otosclerosis declines, fewer surgeons acquire adequate experience in stapes surgery, and even fewer surgeons treat the problems of either complicated or unsuccessful stapedectomy. This chapter presents a comprehensive approach and diagnostic criteria for selection of these unusual patients. Intraoperative problems and solutions are defined and illustrated. The solutions are presented in a logical, safe, stepwise manner to avoid irreversible results.

Before embarking on the nuances of primary and revision stapedectomy, first let us summarize a more recent finding with regard to pregnancy and its effect on otosclerosis. Traditional teaching has assumed that pregnancy would exacerbate otosclerosis. Our evaluation of incidence and progression of otosclerosis in women with children versus childless women has conclusively shown no impact of the pregnancy on further hearing loss in otosclerosis.1

Before addressing technical aspects, a few practical and philosophical points should be presented. When surgery is scheduled, a significant family member or friend should accompany the patient so that another person fully understands the goals and risks of the proposed surgery.

During surgery, the surgeon should terminate the procedure if he or she encounters a problem that might jeopardize the patient’s hearing further. The patient and the surgeon can accept termination more easily than a bad result. The surgeon should not lose focus just to be compulsively neat during stapedectomy. For example, one should not search for the superstructure if it falls into the hypotympanum, should not remove pieces of footplate floating in the perilymph, and should not force on a prosthesis or a wire keeper that is excessively tight. Second-stage procedures can be done.

This chapter reviews the technique of stapedectomy and the principles that prevent misadventures and discusses solutions to unusual problems. In addition, revision techniques for failed stapedectomy are described in detail. Finally, experience is presented in specific areas, such as far advanced otosclerosis with little or no testable hearing, and stapedectomy in children, in elderly patients, in patients with small air-bone gaps, and in fighter pilots. Stapedectomy in the presence of chronic otitis media, the need for promontory drilling, and findings in the other ear in patients with otosclerosis also are summarized.2–4

INTRAOPERATIVE AUDIOMETRY

In the past, surgeons showed the success of stapedectomy when the patient, under local anesthesia, heard sound ranging from a soft whisper to a loud voice. More sophisticated methods are now applied with great success. By using a portable audiometer in the operating room, the surgeon can precisely measure a patient’s hearing before and after surgery. Such improved assessment benefits the surgeon and the patient.

Any portable audiometer can be used. One of the earphones is removed from the headset and inserted into a sterile plastic sleeve, which is available as a disposable orthopedic drill sleeve. The surgeon holds the sterile earphone to the patient’s ear (Fig. 25-1). Testing begins with the presentation of a tone that is easily heard by the patient.

image

FIGURE 25-1 Intraoperative audiometer setup.

Threshold is obtained by progressively decreasing the loudness of the presented tone until the patient cannot hear it. The frequency with the greatest air-bone gap is usually used for single-frequency testing. Circulating nurses can easily learn to operate the audiometer. Hearing is tested at the beginning and the end of the operation to measure changes in hearing resulting from surgery. Despite the disturbed eardrum and blood in the middle ear and in the perilymph, the hearing usually is within 15 dB and often 5 dB from the final hearing result. The result is qualitative, not quantitative, so one is testing for a hearing gain.

Testing by an audiometer in the operating room offers several advantages. First, the surgeon and the patient have instant and accurate feedback on the success of the operation. Second, the improvement of hearing defines the end point of surgery. Third, in revision cases, the surgeon can explore the footplate area without opening the oval window by repositioning the prosthesis in various locations in the oval window. Finally, in difficult cases, different techniques can be attempted to determine the best prosthesis and best placement for optimal hearing.5

ROUTINE STAPEDECTOMY

The basic technique of our routine stapedectomy, which has remained largely unchanged for 43 years, illustrates the principle of a safe approach. Use of this technique and the application of the principles described earlier have closed the air-bone gap in 96% of 17,000 cases. More importantly, overclosure of the air-bone gap occurs in 75% of the cases. Worse hearing ears developed in only 0.5%.

Before surgery, the surgical nurse carefully explains the procedure to each patient. This knowledge helps an otherwise anxious patient to be calm and cooperative. The anesthesiologist or nurse anesthetist begins an intravenous infusion and monitors the patient during the stapedectomy.

The operation begins with the injection in four quadrants of the ear canal with a mixture of 0.5 mL of epinephrine 1:1000 solution and 4.5 mL of 2% lidocaine. This solution results in maximal control of bleeding and minimal cardiovascular changes or symptoms. If the patient remains anxious, intravenous medication is administered in a dose that keeps the patient comfortable, but awake enough to permit intraoperative audiometry.

Each step of the operation should be completed carefully and exactly. Precision in one step makes the next step easier and results in perfection.

The speculum holder, which is always used, is positioned so that each portion of the tympanomeatal flap incision is visible as it is made. The flap should be elevated carefully to prevent damage to the skin and tympanic membrane. As the middle ear is entered, an absorbable gelatin sponge (Gelfoam) pledget soaked in the previously mixed anesthetic solution is placed into the middle ear to anesthetize the middle ear mucosa. As the drum is pushed back, the manubrium of the malleus and incus can be seen and palpated. Any fixation should not preclude completion of the operation, but should be noted so that the patient can be advised later if the hearing result is suboptimal.6

A sharp, strong curette simplifies the task of curetting the ear canal. Enough of the scutum should be removed to see the origin of the stapedius tendon, the facial nerve, and the entire footplate area.

A control hole is placed in the footplate at the junction of the anterior one third and the posterior two thirds of the footplate. The hole may facilitate later removal of the footplate. It also permits early detection of a rare perilymph gusher, when it can be more easily controlled. In addition, if the footplate comes out with the superstructure, the hole reduces the sudden change of pressure in the vestibule. If the footplate is too thick for a needle, the argon laser is used to make the control hole.

After the incudostapedial joint is severed and the tendon is cut, the superstructure is fractured toward the promontory and removed to expose the footplate. The control hole can now be extended across the footplate, and the footplate posterior to the hole is removed. A stapedotomy or partial stapedectomy is done. We have found no significant difference in outcome when comparing stapedotomy, partial stapedectomy, or total stapedectomy except for the lower rate of overclosure in stapedotomies.7 A vein from the forearm, previously harvested, pressed, and prepared, is immediately placed across the oval window with the adventitial side down to seal and protect the vestibule.

Until more recently, the Robinson stainless steel piston prosthesis was used in all cases. This prosthesis comes with either a standard or large well, 0.4 or 0.6 mm stem width, and in various lengths. We have found that a prosthesis with a large well, narrow stem, and length of 4 mm is suitable in 99% of cases, eliminating the need to measure. Instead of the stainless steel prosthesis, we now use the titanium bucket handle prosthesis. With potential future advances in magnetic resonance imaging (MRI) technology in mind, we made the change from stainless steel prosthesis to the titanium prosthesis to optimize MRI compatibility. Results obtained using the titanium prosthesis are equal to the results obtained using the stainless steel prosthesis. In addition to increased MRI compatibility, an advantage offered by use of the titanium prosthesis is that there is no reflection of light from the titanium prosthesis.8 The absence of a reflection enables the surgeon to visualize the placement of the prosthesis better.

The prosthesis is placed by use of a two-handed technique. One hand lifts the incus with an incus hook, while the other gently directs the prosthesis with a strut guide. A controlled study evaluating hearing results with various prosthesis widths revealed similar hearing results in 0.4 and 0.6 mm prostheses. The narrow 0.4 mm stem prosthesis is used because the 0.6 mm prosthesis occasionally can be too wide for a narrow oval window niche.9 Because this prosthesis centers itself in the oval window opening, middle ear packing is not used. The patient’s hearing can be tested immediately after the tympanic membrane is replaced. If the wire keeper does not easily swing over the lenticular process, its use is unnecessary. Forcing it may displace the prosthesis from the center of the oval window (Fig. 25-2).

image

FIGURE 25-2 Routine stapedectomy.

FIGURE 25-3. Lippy modified Robinson prosthesis.

FIGURE 25-4. Modified 4.5 mm Robinson prosthesis in place on vein graft covering oval window.

FIGURE 25-5. Robinson prosthesis in place on mobilized footplate.

FIGURE 25-6. Revision stapedectomy wire prosthesis is pushed aside.

INTRAOPERATIVE PROBLEMS

Tympanomeatal Flap Tear

To avoid tearing the flap as it is lifted, the speculum is repositioned frequently for better vision, especially when dissection is near the annulus, where most tears occur. A torn flap need not stop the operation; it can be repaired by approximation or with tissue, such as vein, fascia, or perichondrium—whatever tissue is used to seal the oval window. In our surgical approach, placement of the vein tissue underneath the tear gives the best result. Enough tissue should have been previously harvested to cover the oval window and to repair any tears or perforations.

Tympanic Membrane Perforation

Tears that involve the tympanic membrane are repaired in the same manner as are tympanomeatal flap tears. When a perforation develops centrally as a result of manipulation, a piece of tissue is placed under the perforation and packed against the tympanic membrane with Gelfoam. The edges of the perforation are not freshened.

Atrophic Tympanic Membrane

An atrophic tympanic membrane may signal a poor blood supply to the incus. An atrophic membrane has been observed on exploration in revision stapedectomy with erosion of the lenticular process being a common finding.10 As in treatment of a perforation, the intact tympanic membrane is reinforced from the underside of the tympanic membrane with tissue. This may be vein, fascia, or, in more severe cases, perichondrium or cartilage. This procedure should thicken the tympanic membrane and protect the incus by providing a better blood supply.

Ossicular Dislocation

During stapedectomy, the incus may be inadvertently loosened in several situations. Loosening may occur when the scutum is curetted away, when a wire is placed on the incus, or when an instrument strikes the incus. If curettage is initiated lateral to the scutum and progresses medially, dislocation is much less likely. The practical solution is to attach a piston stapes prosthesis to the lenticular process to help hold the incus in place. Two thirds of these cases are successful; only a few unsuccessful cases need a revision with a different technique.

Fixed Malleus

The malleus must always be routinely palpated with the same instrument under the surgeon’s direct vision from the underside of the tympanic membrane. The malleus may be slightly fixed, moderately fixed, or totally fixed. If fixation is slight or moderate, the final result of stapedectomy would be as if the malleus had not been fixed at all. The success rate would be the same (96% to 97%), but the overclosure rate would be substantially reduced.11 Partial malleus fixation should be ignored. When the malleus (and probably the incus) is totally fixed, a stapedectomy should be completed, if the patient also has a fixed footplate.

Most of the footplate should be removed to create a large enough oval window opening for a second future procedure (malleus or tympanic membrane to oval window technique). Of totally fixed malleus cases, 68% are successful to within 10 dB, and the air-bone gap is closed to within 10 to 20 dB in an additional 15%. Cases with an air-bone gap of 25 dB or more should be considered for a second-stage procedure. Applying this simple solution over the past 20 years, we have had good hearing results, and no patient with otosclerosis and a fixed malleus has had a further sensorineural hearing loss (Table 25-1).

TABLE 25-1 Malleus-Incus Fixation and Otosclerosis Hearing Results (N = 102)

image

A more complex or possibly traumatic procedure can be postponed until an oval window tissue seal is present. Procedures to free the head of a fixed malleus are usually nonrewarding on a permanent basis.

Fused Incudostapedial Joint

If the joint cannot be separated with a joint knife, the laser can be used instead.

Partial Absence of the Incus

When a partial absence of the long process of the incus is found in a patient with otosclerosis, a stapedectomy is still done. Incus erosion is the second most common finding in revision stapes surgery; a crimped wire prosthesis causes erosion twice as often as the Robinson prosthesis. In place of the standard prosthesis, the Lippy modified Robinson prosthesis is used. The fenestra should be larger than usual because the prosthesis does not self-center.11,12 The technique of prosthesis placement is important to success (see Video 25-1).

The lower stem end of the prosthesis is placed on the vein graft, the upper end with the open well toward the eroded incus. The prosthesis is guided onto the remaining incus from the direction of the promontory. A significant foreshortening of the eroded incus or overhang of the facial nerve necessitates use of an offset Lippy modified prosthesis, yielding more length to avoid the facial nerve.10 In long-term follow-up using the Lippy modified prosthesis in nonrevision cases, initial success (<10 dB air-bone gap) was 90% with long-term hearing (<10 dB air-bone gap) maintained in 86% of patients.10 If the lenticular process comes to a pointed rather than a blunted end, the laser is used to square the end. The laser can also be used to thin or sculpture an incus that is too thick to accept the Lippy modified prosthesis (Figs. 25-3 and 25-4).

Dehiscent Facial Nerve

In otosclerosis surgery, the facial nerve rarely interferes with a stapedectomy except in a congenitally deformed middle ear, or when the facial nerve canal is completely dehiscent. In cases in which more than 50% of the footplate was covered by the facial nerve, the overall success of stapedectomy was similar to that of cases in which the footplate was not covered.13

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