Учебники / Lasers in Otorhinolaryngology Huttenbrink

Fig. 2.21 The incudostapedial joint is divided by vaporizing the stapes capitulum (6 W, pulse duration 0.05 s).

should be taken that the beam does not accidentally strike middle ear structures that lie in the path of the beam (footplate, facial canal). This can be prevented by filling the middle ear with physiologic saline solution or covering these structures with moist gelatin sponge (Gelita or Spongostan). If the posterior crus remnant is still too long after the suprastructure has been removed, it can be vaporized to the level of the footplate using the same laser parameters to obtain better posterior exposure of the footplate.

The anterior crus of the stapes is fractured with a small hook using conventional technique. If all or part of the anterior crus is still visible, it is vaporized with the CO2 laser beam using the same parameters as for the posterior crus. If this does not completely transect the crus, the vaporized site can be fractured using controlled pressure on the small hook. This virtually eliminates the danger of mobilizing the footplate or even partially or completely extracting it. The stapes superstructure is then extracted with a small forceps. Again, it is advisable to protect the surrounding structures (footplate, facial canal) by covering them with moist gelatin sponge or instilling physiologic saline solution.

Fig. 2.23 The stapes footplate is perforated with a single CO2 laser application using the SurgiTouch scanner (20 W, pulse duration 0.04 s, scan diameter 0.6 mm).

After the suprastructure has been removed, the stapedotomy opening is created, usually placing it in the posterior half of the footplate. The goal is to create an approximately round, reproducible fenestra 0.5–0.7 mm in diameter, applying the beam either in a single application (one-shot technique) or in a slightly overlapping pattern (multishot technique), without causing significant thermal alteration of the peripheral zones.

The present author has been able to create a smooth, round fenestra 0.5–0.7 mm in diameter in approximately 70 % of cases with a single 20–22-W laser application of 0.03–0.05- s duration (Fig. 2.23). In cases where a single application did not make an opening of the desired diameter (≤0.3 mm), a second shot was applied to the same site with the scanner or multiple shots were applied without a scanner (approximately 15 % of cases each).

If a scanner is not available, the footplate can be perforated using the multishot technique. A beam 180 µm in diameter is used at a power of 6 W and pulse duration of 0.5 s. From six to 12 shots are needed to create a fenestra 0.5–0.7 mm in size, depending on the footplate thickness.

Fig. 2.25 Intraoperative appearance of obliterative otosclerosis. Otosclerotic foci completely fill the oval window niche.

Care should be taken that the vestibule is filled with perilymph to ensure adequate protection for inner ear structures and prevent damage from direct irradiation. If the perilymph is inadvertently suctioned from the vestibule, no additional laser energy should be applied to the footplate. Lasing of the footplate is continued only after additional fluid has seeped into and adequately filled the vestibule. It may be necessary in some cases to fill the vestibule with physiologic saline solution. A platinum-Teflon piston 0.4–0.6 mm in diameter is then inserted into the fenestra and connected to the long process of the incus (Fig. 2.24). Finally the oval window niche is sealed with connective tissue or clotted blood.

Special Cases

Obliterative Otosclerosis

The incidence of obliterative otosclerosis (Fig. 2.25) is between 2 % and 10 % of all cases [162–165]. It was 5 % in the author’s series. Drilling through a thick footplate obliterating the oval window niche can cause significant vibrationinduced inner ear trauma. The CO2 laser, on the other hand, can vaporize a fenestra in the stapes footplate, regardless of its thickness or degree of fixation, without mechanical trauma to the inner ear.

The settings on the SurgiTouch scanner are the same as for a laser stapedotomy. After the suprastructure is removed,

the otosclerotic foci obliterating the oval window niche are uniformly removed over a broad front by laser application with the SurgiTouch scanner. This is continued until the lateral margins of the oval window can be clearly identified (Fig. 2.26 a). Lower power may have to be used at the periphery of the window niche to avoid accidentally entering the inner ear. Large amounts of char are produced as the bony material is vaporized. Since crystalline char reflects the CO2 laser energy and reduces its ablative effect, it must be removed with a suitable instrument. The vestibule in the posterior part of the oval window niche is opened with the scanner (Fig. 2.26 b) using the same laser parameters as for a one-shot stapedotomy in a footplate without obliterative changes (see Table 2.1). If the diameter of the fenestra is too small to accommodate the prosthesis, the opening can be enlarged either by retreating the same site with the scanner or by applying a concentric pattern of laser flashes without a scanner. The prosthesis is placed in a routine fashion.

Overhanging Facial Nerve

An overhanging tympanic facial nerve segment, whether covered by bone or occasionally exposed, can be a serious obstacle to surgical access. If the facial nerve is covered by bone, the CO2 laser beam can be carefully applied tangentially at low power (1–2 W), using short pulse lengths of 0.05 s, to remove the bone. Scanner settings of 4–5 W, 0.03–0.04 s pulse length, and 0.3–0.4 mm scan diameter are safe and effective. Occasionally this measure is sufficient to obtain a clearer view of the footplate. It is best to avoid completely freeing the facial nerve from its bony covering to protect it from a direct laser strike and prevent nerve prolapse through the resulting bone defect, which can hamper visibility.

In cases where the facial canal completely obstructs access to the oval window niche and removal of the frequently very thin bone will not significantly improve access, or if the tympanic facial nerve segment is not covered by bone, laser use should be suspended in favor of, e. g., a conventional stapedotomy with a curved perforator. Another option for difficult access is to redirect the CO2 laser beam with a mirror. This may enable the surgeon to perforate a footplate that is not directly accessible to the laser beam.

Fig. 2.26 a Uniform vaporization of otosclerotic foci in the oval window niche with the SurgiTouch scanner after removal of the suprastructure. This process creates a large amount of whitish char with higher reflectivity, causing the CO2 laser beam to become ineffective. b The vestibule is opened in the posterior part of the oval window niche.

Floating Footplate

In a conventional stapedotomy, it is not uncommon for manipulations of the stapes to accidentally mobilize the smallest of the ossicles and create a floating footplate, especially if the stapes is partially fixed. Often it is no longer

Fig 2.27 Fenestra made in a floating footplate with the CO2 laser and SurgiTouch scanner (one-shot application technique).

The otosurgeon faces a dilemma when exploring the middle ear of a patient after a failed stapedectomy. To determine the reasons for the conductive hearing loss, the surgeon must test the mobility and integrity of the entire ossicular chain and accurately evaluate the status of the oval window and the position of the prosthesis at the entrance to the vestibule. Often one is unable to determine the depth and lateral margins of the oval window or see the connective tissue covering the structures behind the oval window niche. When palpation of these structures is minimized to avoid inner ear trauma, the surgeon may be unable to identify the exact cause(s) of the conductive hearing loss and therefore cannot provide adequate treatment.

The old prosthesis should be removed with extreme care. If dizziness occurs, the prosthesis should be left in place to avoid permanent inner ear dysfunction. If the prosthesis can be extracted without causing significant inner ear trauma, the new prosthesis (frequently too short) is placed at the presumed center of the oval window niche.

Generally, the patient’s hearing will initially improve if the oval window is free of residual disease and the surgeon’s manipulation has not damaged the inner ear. In many cas-

es, however, the revision does not correct the problem believed to be responsible for most failed stapedectomies: prosthetic migration. The new prosthesis may again migrate out of the oval window niche. The formidable problems that can arise in revision stapedectomies are reflected in the reported success rates of 30–50 %.

Technique of CO2 Laser Revision Stapedotomy

The tympanomeatal flap is outlined and elevated, and the middle ear is inspected. The malleus and incus are probed with a needle to assess their integrity and mobility. Adhesions are frequently present and are vaporized with the CO2 laser using the safe and effective laser parameters determined experimentally (see Table 2.2). With a beam diameter of 0.18 mm, it is sufficient to use a low power setting of 1–2 W with a pulse duration of 0.05 s. When the SurgiTouch scanner is used, settings of 4–8 W, pulse duration 0.03–0.05 s, and scan diameter 0.3–0.7 mm are adequate for soft-tissue ablation. These parameters are used to expose the prosthesis by vaporizing the soft tissue surrounding it (Fig. 2.28 a, b).

In patients with a wire prosthesis (e. g., platinum) attached to a connective tissue graft over the oval window, it is not dangerous to strike the wire directly with the laser beam. If the prosthesis is a piston with Teflon components (e. g., a platinum–Teflon piston), following stapedotomy it should not be struck directly with the beam because the Teflon cannot withstand high temperatures (> 300 °C) and its surface will swell into a “mushroom” shape without disintegrating or combusting.

The prosthesis is exposed by noncontact vaporization of the fibrous attachments. This technique avoids mechanical trauma to the inner ear. Next, the soft tissue covering the oval window niche is uniformly vaporized on a broad front until the lateral margins of the oval window are clearly visualized (Fig. 2.28 c). If the prosthesis is still embedded in connective tissue, the vaporization is continued until it has been completely freed. Once the distal end of the prosthesis has been cleared of all fibrous attachments, it is detached from the incus and extracted with a 90° hook 2 mm long. If dizziness occurs (under local anesthesia), the surgeon should stop all manipulations at once and reinspect

the distal end of the prosthesis for any remaining fibrous attachments that might be pulling on the inner ear.

The tissue at the center of the oval window is then uniformly vaporized to create a fenestra 0.5 mm or 0.7 mm in diameter. Vestibular perilymph should be visible through the opening. Depending on what is found in the oval window (a fibrous neomembrane and/or bony footplate), a 4– 22-W beam with a pulse duration of 0.04 s is applied with a scanner system using one-shot technique, or a 1–6-W beam (pulse duration 0.05 s) is applied in a slightly overlapping pattern of six to12 shots without a scanner.

The length of the revision prosthesis is determined by measuring the distance from the lower surface of the incus to the vestibule and adding 0.2 mm. (The most common is 4.5–4.7 mm.) The prosthesis should extend 0.1–0.2 mm into the fenestra to help prevent recurrent migration. The platinum–Teflon piston is inserted into the fenestra and, if the incus is intact, attached to the neck of the incus. If the incus is badly eroded, a malleovestibulopexy will reestablish sound conduction. Finally, the oval window niche is sealed with connective tissue.

Author’s Results with CO2 Laser Stapedotomy

Results of Initial Operations

Between 1990 and 2002, 365 patients with otosclerosis were treated by CO2 laser stapedotomy. Figure 2.29 shows the mean bone conduction threshold at 0.5, 1, 2, 3, and 4 kHz before CO2 laser stapedotomy and at 1.5–6 months postoperatively. Before surgery the bone conduction threshold was 0.5 kHz at 13 dB HL, 2 kHz at 28 dB HL (Carhart notch), and 4 kHz at 24 dB HL. By 1.5–6 months postoperatively, the mean bone conduction threshold showed improvement of 5 dB at 0.5 kHz, 9 dB at 2 kHz, and 2 dB at 4 kHz, indicating a statistically significant improvement in the bone conduction threshold at all frequencies (the Wilcoxon test, P < 0.01).

At a frequency of 4 kHz, five patients (2 %) showed a decline in postoperative bone conduction threshold to a maximum of 20 dB. None of the patients showed a decline greater than 20 dB. Two patients (1 %) showed a maximum 20-dB

Fig. 2.28 a Adhesions between the prosthesis and middle ear mucosa. b Noncontact exposure of a wire-connective tissue prosthesis by vaporization of the surrounding soft tissue with the CO2 laser beam.

c Uniform vaporization of the soft tissue covering the oval window niche. The margins of the oval window are clearly identified.

Frequency (kHz)

Hearing loss (dB)

Preoperative

1.5–6 Months postoperative

Fig. 2.29 Hearing results after CO2 laser stapedotomy. Mean bone conduction threshold: preoperatively and 1.5–6 months postoperatively (n = 235).

n = 235

decrease in bone conduction threshold in the normal speech range (0.5, 1, 2, and 3 kHz). There were no instances of deafness.

Comparison of the mean preand postoperative air–bone gap in 213 patients who were followed for at least 1 year (1– 9 years) is shown in Fig. 2.30. The air–bone gap improved steadily during the first year. After 1 year the air–bone gap was ≤20 dB in 98 % of the patients (0–10 dB in 71 %, 11– 20 dB in 27 %). Three patients (1 %) developed an air–bone gap >30 dB and had to undergo revision. The air–bone gap following the revision was in the range of 11–20 dB.

The mean hearing loss for numbers by air conduction improved from 48 dB HL before surgery to 23 dB HL after surgery, with a follow-up period of 1 year or more.

Complications in Primary Operations

No intraoperative complications arose in any of the primary operations. Two patients (0.5 %) experienced mild postoperative sensorineural hearing loss, and one patient had moderate sensorineural loss. Granulomas were found in two revision operations. One patient complained of tinnitus that had not been present before the surgery, and two patients reported exacerbation of preexisting tinnitus. Nine patients developed persistent dizziness caused by a

% Patients

Fig. 2.30 Hearing results after CO2 laser stapedotomy. Distribution of patients with a postoperative air–bone gap of 0–10 dB, 11–20 dB, 21– 30 dB, and >30 dB (n = 213).

prosthesis that was too long, which resolved after a shorter revision prosthesis was inserted.

Another 13 patients underwent revision surgery due to recurrence of conductive hearing loss within a period of 6 months to 51ßw years. In six cases the prosthesis was displaced out of the stapedotomy opening. Prosthetic migration was combined with partial incus erosion in two cases and with total incus erosion in three cases. In two of six patients, the prosthesis was too short. In all cases the prosthesis was attached to the residual incus. Other reasons for conductive hearing loss without prosthetic migration were a too-short prosthesis in two cases and loosening of the eyelet in four cases. In one patient the eyelet was loose and the prosthesis was fixed to the incus by adhesions. Hearing improved after the adhesions were removed with the laser and the prosthesis was reattached to the incus.

Results of Revision Operations

Sixty-eight patients with otosclerosis underwent CO2 laser revision stapedotomy. Twenty-one of the patients had undergone stapedectomy with insertion of a Schuknechttype wire-connective tissue prosthesis, 45 had undergone stapedotomy with implantation of a platinum-Teflon piston, two had a gold prosthesis, one had a Causse Teflon prosthesis, and two had undergone stapes mobilization.

Analysis of the postoperative pure-tone audiograms of 46 patients at 1.5–6 months postoperatively showed a significant improvement in the average bone conduction threshold for 0.5, 1, 2, 3, and 4 kHz (the Wilcoxon test, P < 0.05) (Fig. 2.31). The average improvements were 4 dB at 0.5 kHz, 3 dB at 2 kHz, and 6 dB at 4 kHz.

Seventeen patients (25 %) had a maximum decrease of 10 dB in their postoperative bone conduction threshold. Two patients (3 %) had a postoperative hearing loss greater than 10 dB for at least one frequency (maximum of 35 dB in one case). One of these patients (1 %) had hearing loss over the normal speech range (0.5, 1, 2, 3 kHz), and the other patient (1 %) had hearing loss only at 4 kHz. No instances of early or late deafness were observed.

Figure 2.32 shows the average air-bone gap at 0.5, 1, 2, and 3 kHz in 30 patients ≥1 year (1–9 years) after surgery com-

Frequency (kHz)

Hearing loss (dB)

Preoperative

1.5–6 Months postoperative

Fig. 2.31 Hearing results after revision CO2 laser stapedotomy. Average bone conduction threshold preoperatively and 1.5–6 months postoperatively (n = 46).

pared with preoperative findings. The air–bone gap improved steadily during the first year. At 1 year it was 0– 10 dB in 60 % of operated patients, 11–20 dB in 33 %, and 21–30 dB in 7 %. Thus, the air–bone gap was 20 dB or less in 93 % of the patients. None of the patients had an air–bone gap >30 dB.

The analysis of speech audiograms in 30 patients showed that the mean air-conduction hearing loss for numbers improved from 49 dB HL to 32 dB HL by 1 year or more after the surgery.

Complications of Revision Operations

In one case the vestibule was opened prematurely at operation, with possible laser irradiation of the empty vestibule. Postoperatively the patient had a moderate pancochlear sensorineural hearing loss of approximately 40 dB with accompanying tinnitus. One woman developed a moderate pancochlear sensorineural hearing loss of approximately 40 dB 1 week after the operation, which subsequently improved to 15 dB. One patient underwent revision 6 months postoperatively due to an increase in sensorineural hearing loss. The hearing loss improved after adhesions between the prosthesis and tympanic membrane were cleared and the tympanic membrane was reinforced

% Patients

Fig. 2.32 Hearing results after revision CO2 laser stapedotomy. Distribution of patients with a postoperative air–bone gap of 0–10 dB, 11– 20 dB, 21–30 dB, and >30 dB (n = 30).

posterosuperiorly with a perichondrial graft. None of the patients complained of persistent dizziness.

Laser Versus Conventional Surgery

Before a new technique can become established, its success rates must be compared with those of traditional techniques. This comparison is difficult to make, however, due to differences in recruitment and data analysis. For example, while the average air–bone gap in older studies was determined for frequencies of 0.5, 1, and 2 kHz, it is additionally determined for 3 kHz in more recent studies.

Nevertheless, a comparison of the results in major publications shows that the postoperative hearing gain after primary laser stapedotomy [15, 29, 38, 80, 84, 87, 148, 173, 174] does not differ from the good results of conventional surgery [73, 86, 149, 164, 175–183]. The results published in the literature clearly demonstrate, however, that complications after CO2 laser stapedotomy are less frequent and less severe than after conventional operations [32, 84, 87, 149]. The present author’s results are consistent with these findings.

Laser use in revision surgery offers significant advantages over conventional technique. The principal advantages are improved diagnostic and therapeutic precision, the ability to better stabilize the new prosthesis at the center of the oval window niche, and the reduction of inner ear trauma. Based on an improvement of the air–bone gap to 20 dB or less, the success rates with laser revision surgery were 70– 92 % compared with 49–85 % with conventional surgery. The higher success rates and lower complication rates are statistically significant and do not depend on the type of laser system used [15, 32, 39, 79, 81, 125, 184–186].

The CO2 laser appears to be suitable for use in stapes surgery. With advances in laser technology, one-shot stapedotomy can be done in most patients. With strict adherence to recommended settings, the laser helps to optimize this very exacting procedure and should reduce the incidence of inner ear damage. It is superior to conventional techniques, particularly in the surgery of obliterative otosclerosis and in revision procedures.

Peripheral Vestibular Disorders: Benign

Paroxysmal Positional Vertigo and

Endolymphatic Hydrops

Conventional labyrinthectomy has been proposed as a last recourse for the treatment of chronic, intractable peripheral vestibular disorders, although the indications are limited due to the resultant hearing impairment and vestibular compensation. It is already known that abnormalities of the inner ear fluids can cause macular dysfunction [189, 190]. Earlier studies also demonstrated involvement of the maculae in a setting of perilymphatic and endolymphatic hypertension [189]. Moreover, clinical observations show that macular dysfunction is often present in acute and recurring peripheral vestibular disorders. For this reason, the selective induction of macular damage without altering the function of the ampullary crest and cochlea would result in minimal surgical trauma and functional deficits. In experiments where the otolithic organs of guinea pigs were irradiated through the oval window with the argon laser after stapedectomy, morphologic studies revealed degeneration of the macula utriculi and macula sacculi [191]. The semicircular canals and cochlea remained intact, suggesting that it was possible to preserve hearing. This surgical procedure was first performed clinically in a 62-year-old woman who developed benign paroxysmal positional vertigo (BPPV) after the closure of a perilymph fistula [192]. The macula utriculi was lased with an argon beam through the stapedectomized oval window (1.5 W, pulse duration 0.5 s), and the oval window was subsequently sealed with perichondrium. A Teflon prosthesis was then inserted as in a conventional stapedotomy. Two years after the surgery, the patient was completely free of vertigo and her hearing was unchanged. Selective lasing of the macula sacculi is problematic, however, because the wall of the saccule contains pigment and may be perforated by an argon laser beam [193].

Antonelli et al. [198] investigated mechanical versus CO2 laser-assisted occlusion of the posterior semicircular canal in a prospective study of six patients with intractable BPPV. While postoperative dysequilibrium resolved in all of the CO2 laser-treated patients, who were hospitalized for an average of 2.8 days, dysequilibrium persisted in four of the six patients treated by mechanical canal occlusion and required an average hospital stay of 5.2 days. Hearing was not significantly different between the two groups, and neither group had clinically significant postoperative hearing loss. The authors concluded that the incidence of persistent dysequilibrium after posterior semicircular canal occlusion could be reduced by using the CO2 laser to seal the membranous canal prior to occluding the bony canal.

Westhofen [199] described the selective ablation of the otolithic organs in guinea pigs with an argon laser beam applied through the intact footplate. The observation of vestibulospinal responses and the analysis of histomorphologic findings indicated functional obliteration of the maculae during the first few postoperative days and rapid vestibular compensation after four days. Given the limitations imposed by the animal model (guinea pig footplate thinner than in humans, difficult to detect vestibular disorders in the selected species), these results are not applicable to human patients. In a more recent animal study, Adamczyk and Antonelli [200] reported on the selective KTP laser-assisted ablation of all three semicircular canals in guinea pigs with experimentally induced endolymphatic hydrops following unilateral closure of the endolymphatic duct. The canals were ablated without the need for extensive fenestration of the bony labyrinth. Electrocochleographic and histologic studies showed no changes in the cochlea. This technique could prove useful in the treatment of severe, intractable Ménière’s disease.