Otology & Neurotology

31:381Y384 Ó 2010, Otology & Neurotology, Inc.

Cavitating Otosclerosis: Clinical, Radiologic,

and Histopathologic Correlations

*Andres O. Makarem, †Thu-Anh Hoang, ‡William W. M. Lo,

*Fred H. Linthicum, Jr., and *Jose N. Fayad

*Department of Histopathology, House Ear Institute; ÞDepartment of Radiology, UCLA Medical Center;
and þDepartment of Radiology, St. Vincent Medical Center, Los Angeles, California, U.S.A.

Background: Despite the high prevalence of otosclerosis and Results: Two cases of cochlear otosclerosis presented with a
its having long been a subject of scrutiny, cavitary changes in clinical syndrome possibly attributed to the existence of a cav-
otosclerosis are rare and not well known. Here, we describe and ity within the otosclerotic foci.
introduce into the literature the unusual histologic and radiolo- Conclusion: Cavitating otosclerosis is a not well-known oc-
gic findings of cavitation and its possible clinical relevance in currence in patients with advanced cochlear otosclerosis,
patients with advanced cochlear otosclerosis. and it is a possible cause of a ‘‘third window’’ syndrome and
Methods: Cases with clinical otosclerosis and presence of surgical complications. Key Words: AdvancedVCavitaryV
cavitation were selected from our temporal bone collec- CavitatingVCochlearVComplicationVGusherVThird
tion and correlated with premortem imaging and clinical windowVHistopathologyVOtosclerosisVOtospongiosis.
manifestations. Otol Neurotol 31:381Y384, 2010.

Otosclerosis was first described in 1735 by Valsalva loss, referred to as Blabyrinthine otosclerosis[ (6). Oto-
(1) as ankylosis of the stapes to the margins of the oval sclerosis is one of the most common causes of conduc-
window. Later, in 1841, Toynbee (2) described osseous tive hearing loss (clinical otosclerosis), yet most cases of
anchylosis of the stapes to the fenestra ovalis as one of otosclerosis are asymptomatic and only diagnosed as
the common causes of deafness. The term sclerosis was incidental findings in temporal bone autopsies (histologic
introduced in 1881 by von Troltsch (3) with the thought otosclerosis). These changes can occur at many locations
that sclerosis of the tympanic mucosa caused the fixation in the inner ear. Most cases consist of changes in the oval
of the stapes, and although in 1893 Politzer (4) discov- window, but they have also been described in the round
ered the true pathology to be in the labyrinthine capsule, window, cochlear apex, posterior to the oval window,
the term otosclerosis has remained in use. posterior and anterior wall of the internal auditory
Otosclerosis (Ous, ear; skleros, hard; osis, condition) canal (IAC), cochlear aqueduct, semicircular canals,
is a distinctive bone dyscrasia known only to affect and within the stapes footplate (7).
humans. It consists of 1 or several circumscribed foci Histopathologically, the disease is composed of active
of new, softer, and more vascular bone that replace the and inactive foci. Under light microscopy, active lesions
remarkably avascular endochondrial bone of the adult (otospongiosis) can be recognized by their spongy struc-
labyrinthine capsule (5). The process can spread across ture and immature osseous tissue, by the size of the mar-
the stapedial annular ligament and fix the stapes, produ- row spaces that contain a very cellular connective tissue
cing a conductive loss, or it can surround the cochlea and with numerous osteoclastic giant cells, and, most impor-
parts of the labyrinth, causing a sensorineural hearing tantly, by an increased and dilated vascularity. This cor-
responds to the areas undergoing active resorption by
numerous multinucleated osteoclastic giant cells. Within
Address correspondence and reprint requests to Fred H. Linthicum, Jr., the perivascular connective tissue, fibroblasts take the
M.D., 2100 West 3rd Street, Los Angeles, CA 90057; E-mail: flinthicum@ characteristics of the osteoblasts, osteocytes are more nu-
hei.org merous, large, and plump compared with normal bone,

381
382 A. O. MAKAREM ET AL.

Following Health Insurance Portability and Accountability

Act regulations for protection of patient privacy, medical re-
cords were analyzed for a clear clinical and surgical history.

RESULTS
Case 1
A 41-year-old man presented with a conductive hear-
ing loss in his right ear. A right stapes mobilization was
done 5 years later with some improvement but failed to
close the air-bone gap. Because of the persistent gap, a
stapedectomy with a polyethylene strut on a vein graft
FIG. 1. Histologic section of right temporal bone shows otosclero-
sis (small arrows) surrounding a cavity (ca) that is continuous with
was done, but again, a 20 dB gap remained. Another revi-
the internal auditory canal and contains some loose fibrous tissue. sion with a piston also failed to close the gap, and he was
The process has eroded the endosteal bone leaving only a fibrous diagnosed with Binner ear conductive hearing loss.[
membrane between the cochlear basal segment and the cavity Histologic examination of the right temporal bone
(large arrow). sc indicates otosclerosis; sp, otospongiosis. H&E 15. (Fig. 1) shows an opening through the obliterated foot-
plate with a space for the prosthesis. There is a large
otospongiotic and sclerotic lesion at the posterior apex
and a new immature basophilic fiber bone is laid down of the cochlea and also involving the usual site of the
in a web-like pattern, which takes a bluish stain with he- fissula antefenestram. It extends to the wall of the
matoxylin and eosin (H&E). Inactive lesions (otosclerosis) cochlea, particularly the basal turn where there is hyalin-
are characterized by solid compact mosaic-like osseous ization of the spiral ligament. There is a large cavitation
tissue that contains few and small marrow spaces as well of the anterior inferior internal auditory canal by the
as infrequent and small blood vessels. This corresponds to otosclerotic process, which extends as far anteriorly as
the resorption of immature bone and its replacement by an the edge of the basal turn of the cochlea. There is no bone
osseous tissue with less ground substance and more col- between this excavation and the scala tympani, leaving
lagen fibers, which take a reddish color when stained with only periosteum separating the two.
H&E. Here, the osteocytes are fewer, smaller, and more
mature. These steps go on continuously and irregularly
within a focus (8). Case 2
Cochlear otosclerosis (CO) is defined as a sensori- A 47-year-old man experienced progressive hearing
neural hearing loss in the presence of, and presumably loss bilaterally over several years. He had a left stape-
due to, an otosclerotic focus in the cochlear capsule with- dectomy and a subsequent revision. He did well with a
out associated stapes fixation (7). Cochlear otosclerosis left hearing aid until he became acutely deaf in the left
is well known and has been described in the literature,
but so far, there has been no mention of cavity forma-
tions in cochlear otosclerosis foci. However, Schuknecht
(9) has shown histologic sections that satisfy the criteria
for bilateral cochlear otosclerosis in which both temporal
bones exhibit severe cavitating otosclerosis with bilateral
severe sensorineural hearing loss.

METHODS
The temporal bone bank at our institution has 11 cases of
neurosensory hearing loss that histopathologically fulfill cri-
teria for a diagnosis of otosclerosis with cavitation. Of these
bones, 3 cases present the cavitation in a pericochlear otoscle-
rotic focus, 4 in a focus related to the IAC, and 4 cases present
with both. We describe 2 cases in which the cavitating otoscle-
rosis presents with clinical and surgical relevance.
The temporal bones that were donated to the House Ear
Institute were decalcified in EDTA for 8 to 12 months and
later processed for celloidin embedding. The bones were then
cut with a width of 20 Km, and every 10th section was stained FIG. 2. A, Precochlear implant CT shows pericochlear cavity.
with H&E. These sections were placed on slides and described B, Computed tomography of left cochlear implant shows elec-
under light microscopy. Histologic findings were recorded and trode array traversing inferior segment of basal turn and curving
stored with the samples in the Institute’s temporal bone bank. anteriorly into a pericochlear cavity.

Otology & Neurotology, Vol. 31, No. 3, 2010

 CAVITATING OTOSCLEROSIS 383

ear following coughing fits. Preoperative computed to-

mography (CT) showed essentially symmetric, bilateral,
extensive multifocal, and coalescent hypoattenuations
in the cochlear capsules consistent with otosclerosis, as
well as a focus approximating cerebrospinal fluid (CSF)
in attenuation value (Fig. 2A). A left cochlear implanta-
tion encountered a CSF leak, which the surgeon sealed
with a muscle plug, and concluded as partial implanta-
tion. An immediate postimplant CT showed the tip of the
electrode array curving anteriorly out of the inferior seg-
ment of the basal turn into the otic capsule (Fig. 2B).
Postoperative audiology reports showed the patient’s
inability to hear on the implanted side.
The patient was later referred for a right cochlear
implant. At surgery, the round window was completely
obliterated by otosclerotic bone. A CSF gusher was again FIG. 4. A, Computed tomography demonstrates cavitating oto-
encountered at cochleostomy and controlled by muscle sclerosis with pericochlear cavities, one of which communicates
packing. The surgeon proceeded to drill again in a more with the internal auditory canal near the fundus (arrow). B, Histo-
logic section of right temporal bone of another patient with com-
superior location and exposed the true cochlear lumen, parable disease shows otosclerosis cavity (Cav) in continuity (*)
which did not present with a CSF leak, and was able to with the IAC communicating with the cerebral spinal fluid space.
introduce the full length of the electrode. H&E 8.

DISCUSSION canal, and Paget disease, the most common being a

dehiscence of the superior semicircular canal (11), but
The first case describes a patient with conductive hear-
there is no description in the literature regarding this
ing loss due to the existence of a Bthird window,[ which
syndrome being caused by a cavity formation within an
is a potential connection to the membranous labyrinth
otosclerotic focus that is continuous with CSF.
beyond the oval and round window (10). Such a connec-
The second case shows the relevance of a cavitating
tion can channel the inner ear fluid wave made by sound
otosclerotic focus in the surgical field. A patient who has
energy entering through the oval window away from the
bilateral cavitating otosclerosis presented with a compli-
basilar membrane but would have no effect on bone con-
cation specific for a connection between the CSF and
duction. Many causes for a Bthird window[ have been
cochlear lumen. The cavities were large enough to con-
identified and described, including dehiscence of the
tain the greater part of an electrode array of a cochlear
semicircular canals, large vestibular aqueduct syndrome,
implant (Fig. 3); they connected with the IAC (Fig. 4)
DFN-3, dehiscence between the cochlea and carotid
and filled with CSF, which explains the gushers encoun-
tered during the procedures.
Otosclerosis/spongiosis, whether fenestral or cochlear,
is best demonstrated by high-resolution CT. Sclerotic foci
are mildly hypoattenuating compared with normal bone
of the otic capsule. Spongiotic foci approach soft-tissues
in attenuation. Cavitating foci, which may communicate
with the CSF space in the internal auditory canal, as
shown in Case 2, approximate CSF in attenuation. Rarely,
osteogenesis imperfecta or tertiary otosyphilis may sim-
ulate florid otosclerosis, but the bone lesions tend to be
less confined to the enchondral cochlear capsule. Recog-
nizing cavitating otosclerosis by preimplant CT may help
the surgeon prepare for possible CSF leak and avoid elec-
trode misplacement into a pericochlear cavity.

CONCLUSION

FIG. 3. A, Computed tomography reveals pericochlear cavities, Although the pathophysiology of a cavity formation in
one of which is in a periapical location. B, Histologic section of an otosclerosis focus is not yet understood, the cases
right temporal bone of another patient with comparable disease described provide evidence that cavitating otosclerosis
shows substantial otosclerosis foci (Oto) with a large cavity (Cav)
capping (anterior and lateral to) the apex of the cochlea. FN indi- may be an additional cause of Bthird window[ lesions,
cates facial nerve; IAC, internal auditory canal; ME, middle ear; and it is a potential cause for CSF gushing and electrode
TM, tympanic membrane; V vestibule. H&E 8. misplacement at cochlear implantation.

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384 A. O. MAKAREM ET AL.

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Otology & Neurotology, Vol. 31, No. 3, 2010