Stapes mobilization in otoscierosis.

Abstract

We performed a retrospective chart study (including surgeon's notes and audiometric results) and an analysis of the archival temporal bones from a patient who had undergone surgery for stapes mobilization in both ears. The stapes footplate was submerged into the vestibule on the right (as a complication of surgery) and absent on the left. One interesting finding was that the patient's hearing had improved on the right despite the presence of the depressed footplate and that the air-bone gap had widened on the left despite the absence of complications on that side.

Introduction

Otoscierosis is a hereditary, localized disease of the bone of the otic capsule. The disease process involves the removal of mature lamellar bone by osteoclasts and its replacement with bone of greater thickness, cellularity, and vascularity. Otoscierosis can cause a conductive bearing loss, a mixed loss, and occasionally a purely sensorineural hearing loss.

Kessel performed the first stapes mobilization in 1878. [1] In 1900, Siebenmann condemned stapes mobilization, and the procedure remained discredited for decades afterward. [2] In 1952, Rosen gained recognition for rediscovering mobilization during a fenestration operation, and he reintroduced it as a treatment for otosclerosis. [3] Today, however, stapes mobilization is rarely used to treat otosclerosis, although it might still have some usefulness in unusual cases.

In this article, we describe the case of a patient who had undergone multiple stapes mobilization procedures in both ears as a treatment for otoscierosis.

Clinical history

We selected from our archival collection a right and left temporal bone that had been removed at autopsy in 1993. Forty-four years earlier, the patient had undergone a bilateral stapes mobilization procedure for otosclerosis. Information from the patient's chart and from a questionnaire the patient had completed was abstracted for relevant clinical information. The histopathologic findings in this case provide insight into the surgical complications and audiometric results that can occur following stapes mobilization surgery.

The patient was a white woman whose otologic history dated back to her childhood. She was 81 years old at the time of her death, when the temporal bones were harvested. According to the chart, she had experienced frequent drainage from the right ear from the time of her infancy until the age of 5 years. She had not noticed any hearing loss until she had reached the age of 26 years. An assessment by an otolaryngologist at that time revealed that the woman had practically no hearing in her right ear. However, nothing was done to treat the hearing loss.

In 1949, when the patient was 37 years old, she developed otitis media in the left ear. She underwent myringotomy and healed without complication. In 1959, an otolaryngologist diagnosed bilateral otosclerosis that was more severe on the right. The surgeon performed stapes mobilization on the right, but the woman' shearing did not immediately improve. One month later, she underwent stapes mobilization on the left, and she noted an immediate improvement in her hearing that remained stable during followup visits.

Because the first surgery had not improved the patient's hearing on the right, she underwent vein plug stapedioplasty on that side 1 year later. According to the surgeon's notes, the stapes superstructure was found intraoperatively to be leaning against the promontory. The surgeon had attempted to remove the superstructure, but it fell into the attic and could not be retrieved. The surgeon described the footplate of the stapes as "springy and flexible." Attempts to mobilize the footplate were unsuccessful; it was depressed into the vestibule and was suspended by its anterior attachment. A vein plug was placed over the oval window, and a wire prosthesis was looped around the incus and crimped into position.

The patient had undergone pure-tone audiography just prior to her previous surgery in 1959 and regularly thereafter for 9 years (table). One month postoperatively, the air-bone gap on the right had been reduced by almost 50%; during the subsequent 9 years, the level fluctuated between 12.5 and 29.2 dB. Her speech discrimination score had improved to 100% 1 year after surgery, and it remained fairly constant thereafter. These audiograms also revealed that the patient had a high-frequency sensorineural hearing loss on both sides, which was probably presbycusis.

In a questionnaire completed by the patient in 1987, when she was 75 years old, she indicated that she was experiencing tinnitus and vertigo in addition to her diminished hearing.

Temporal bone histopathology

We prepared the temporal bone samples for histopathologic analysis. The temporal bones were fixed, decalcified, and embedded in celloidin. Sections were then cut at a thickness of 20 [micro]m, and every tenth section was stained with hematoxylin and eosin and examined under light microscopy.

On the right side, the middle ear cavity was normal except for a small amount of blood in the posterior epitympanum and mesotympanum, which was probably an artifact of the bone removal. The otosclerotic focus extended from the labyrinthine capsule through the fissula ante fenestram and into the round window niche (figure). The stapes superstructure was adherent to the posterior part of the pars flaccida and the posterosuperior portion of the pars tensa. The footplate of the stapes was depressed into the vestibule and suspended by its anterior attachment to the oval window. Fibrous tissue was present between the footplate and the anterior edge of the oval window, and osteitis was noted in the long process of the incus. The tympanic membrane was atelectatic and was marked by coexisting atrophy and perforation in the inferior quadrants. Late-stage tympanosclerosis was present in the inferior quadrants of the pars tensa.

On the left side, the otosclerotic focus extended from the labyrinthine capsule, through the fissula ante fenestram, and into the round window niche. The footplate of the stapes was absent, and the vestibule was sealed off from the middle ear by fibrous tissue. A slight degree of osteitis was seen in the long process of the incus. The posterosuperior quadrant of the pars tensa was thickened, and some areas had been destroyed during processing. The inferior quadrants showed late-stage tympanoscierosis. The middle ear was normal.

Discussion

A floating footplate is a rare ([less than]1% of cases) but potentially serious complication of stapes surgery. Attempts to extract the footplate can result in a "dead ear" or a submerged or depressed footplate. [1]

The management approach to submerged footplate fragments depends on their size. Small fragments cause minimal adverse effects and should be left alone. Larger fragments often do not diminish hearing, but they might cause persistent postural vertigo. [2] Larger fragments can be removed by placing several drops of blood in the vestibule, allowing them to clot and coat the fragments, and removing the coated fragments with gentle aspiration. [3] Another method advocated for managing a mobilized footplate is to place a vein graft over the footplate and then insert a Robinson prosthesis. [4] In our patient, whose footplate in the right ear was submerged, the surgeon had placed a vein graft over the oval window and used a wire prosthesis, because any manipulation of the footplate during an attempt to remove it might have resulted in a dead ear.

In our patient, the air-bone gap on the right remained less than 20 dB for 8 years postoperatively and then increased to 29.2 dB at year 9 (table). On the left, the widening of the air-bone gap had occurred earlier and was more severe, which was surprising because it was the right ear that had undergone revision stapes mobilization and had experienced the associated complication of the submerged footplate. This set of circumstances demonstrates that appropriate management in the event of an intraoperative complication can prevent an adverse clinical outcome. These patients should, however, be monitored with diligent followup.

The surgeon's candor in writing his operating notes and his regular followup of the patient made the clinical and histopathologic correlations of this case more meaningful and relevant. Thorough documentation of clinical findings is important not only for treatment, but as a contribution to future studies of archival samples. Since the advent of stapedectomy and stapedotomy, stapes mobilization is rarely used to treat otosclerosis. However, this procedure is useful for mobilizing the stapes during tympanoplasty when stapes fixation by tympanosclerosis is discovered. [5]

References

(1.) Kessel J. Uber das Mobilisiener des Steigbugels durch Ausschneiden des Trommelfelles, Hammers und Amboss bei undurch gangigkeit der Tuba. Arch Ohrenh 1878;13:69-88.

(2.) Siebenmann F. Sur le traitment chirurgical de la scierose otique. Congr Int Med Sect Otol 1900;13:170-7.

(3.) Rosen S. Palpation of stapes for fixation: Preliminary procedure to determine fenestration suitability for otosclerosis. Arch Otolaryngol 1952;56:610-5.

(4.) Causse J, Causse JB. Eighteen-year report on stapedectomy. I. Problems of stapedial fixation. Clin Otolaryngol 1980;5:49-59.

(5.) Meyerhoff WL, Paparella MM. Management of otosclerosis. In: Paparella MM, Shumrick DA, Gluckman JL, Meyerhoff WL, eds. Otolaryngology. Philadelphia: W.B. saunders, 1991:1489-512.

Table. Sequential pure-tone audiogram results
                   Air-bone gap (dB)        Mean AC + threshold
Date *                   Right        Left         Right         Left
10/1/59 (preop)            -          19.2         59.2          25.8
10/2/59 (surgery,        34.2          -           40.8           -
right ear)
1 mo postop              17.5          -           29.2          24.2
1 yr postop              14.2         17.2         22.5          24.2
2yrpostop                12.5          -           20.8          27.5
3yrpostop                14.2          -           27.5          27.5
4 yr postop              17.5          -           22.5          32.5
6 yr postop              15.8          -           22.5          35.8
7 yr postop              19.2         40.8         24.2          40.8
8 yr postop              17.5         45.8         24.2          44.2
9 yr postop              29.2         39.2         32.5          44.2
                     SDS +        SRT +
Date *             (%), right  (db), right
10/1/59 (preop)        96          56
10/2/59 (surgery,     100          34
right ear)
1 mo postop            68          26
1 yr postop           100          18
2yrpostop              96          18
3yrpostop              92          18
4 yr postop            92          18
6 yr postop            88          18
7 yr postop            92          17
8 yr postop           100          17
9 yr postop            92          18
(*)Audiograms originally recorded under
the 1951 ASA standard have been updated
to reflect the newer 1964 ISO standard.
(+)AC = air conductions; SDS = speech
discrimination score; SRT + speech
reception threshold.