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Acta Otorrinolaringol Esp. 2015;66(6):356---358
www.elsevier.es/otorrino
CASE STUDY
Exostosis of the Internal Auditory Canal: 10-Year
Follow-Up夽
Exostosis del conducto auditivo interno: 10 años de seguimento
Guilherme Vianna Coelho,∗ Guilherme Machado de Carvalho,∗
Alexandre Caixeta Guimarães, Leopoldo Nizam Pfeilsticker
Ear, Nose, Throat and Head & Neck Surgery Department, Campinas University, UNICAMP, Campinas, São Paulo, Brazil
Received 3 April 2014; accepted 20 May 2014
Case Report
A 45-year-old female patient was attended with a right pulsatile tinnitus that had appeared two years ago. The tinnitus
gets better when the patient turns the head/neck to the
right or perform a hand compression of the neck in the right
carotid. The tinnitus follows the cardiac rhythm and gets
worse when she practices exercises.
There was no other symptoms, such as hypoacusis, dizziness, or pain, and the patient had no previous medical
history. Physical examination had no abnormalities.
Audiogram showed a normal response with normal pure
tones scores, speech recognition in 10 dB in both sides and
good sound discrimination (96% of correct answer at 50 dB).
Normal tympanometry on both sides (type A).
The temporal and skull base CT (02/06/2002) showed a
bone lesion in the left IAC, narrowing the canal, as the MRI
(28/06/2001) that appointed out the same lesion. There is
also a finding in the MRI of an empty sella (Fig. 1)
The cervical Doppler of carotid and vertebral vessels
(01/09/2000) was normal.
夽
Please cite this article as: Coelho GV, de Carvalho GM, Guimarães
AC, Pfeilsticker LN. Exostosis del conducto auditivo interno: 10 años
de seguimento. Acta Otorrinolaringol Esp. 2015;66:356---358.
∗ Corresponding authors.
E-mail address: [email protected] (G.V. Coelho).
After 10 years of follow-up, the patient had total resolution of the tinnitus. She only complained of a mild headache
in the right temporal area, that occurs occasionally and gets
better with analgesics.
The audiogram showed no alterations in relation to the
previous exam, maintaining a normal tympanometry (type
A bilateral). The auditory brainstem response was normal
in terms of latency intervals and latency values and she
had normal vestibular function in the electronystagmography exam.
A new CT and MRI showed no considerable growth of the
exostoses and no radiological changes in the lesion of IAC
was found (Fig. 2).
Discussion
Exostoses are benign lesions frequent in external auditory canal and head and neck region but very rare in
the internal auditory canal (IAC).1,2 There are not many
cases described in the literature, Pubmed presents only 14
manuscripts.3
The clinical presentation of internal auditory canal exostoses varies, most cases are asymptomatic, but in some
cases they can cause tinnitus, vertigo, hearing loss and
even brainstem compression, mimicking symptoms of vestibular schwanommas.4 The diagnosis can be suggested by
an internal auditory canal narrowing in magnetic resonance
imaging (MRI), but is confirmed by high resolution computed
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Exostosis of the Internal Auditory Canal
357
Figure 1
CT and MRI of 2002.
Figure 2
CT and MRI of 2012.
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358
tomography (CT) scan which demonstrate smooth-bordered
broad-based lesions.
Microscopically, exostoses show parallel concentric layers of subperiosteal bone, no fibrovascular channels and
abundant osteocytes. Osteomas, on the other hand, are
pedunculated lesions, have minimal osteocytes and contain
fibrovascular channels surrounded by lamellar bone.1
The differential diagnosis of lesions in the internal
auditory canal include congenital malformation, extensive otosclerosis, cranial hyperostosis, fibrous dysplasia,
osteopetrosis, Paget’s disease and neoplasic bony tumours,
such as exostoses and osteomas.6,4 Sometimes it is difficult
to properly differentiate between these last two, since they
have similar clinical presentation and tissue biopsy of the
internal auditory canal is an invasive procedure. The diagnosis is made by the different characteristics on the CT:
exostoses appear as broad based bony growth, with a smooth
border, and osteomas are usually dense bone pedunculated
solitary lesions, with radiologic evidence of bone marrow.1,3
For patients with severe symptoms, current literature
supports surgery to remove local nerve compression. Davis
et al.5 analyzed 12 patients with symptomatic IAC osteomas
from the literature, of which 8 underwent surgical removal.
Complete cure of all symptoms was observed in only 3 of
these patients, but they all noted some improvement. The
result was better in patients with tinnitus and vestibular dysfunctions, and patients with hearing loss did not had a very
good outcome. This may due to continuous compensation by
the contralateral labyrinth in the first cases.5
Asymptomatic patients should be followed-up with regular CT scans and audiological and vestibular tests.1 Our
G.V. Coelho et al.
patient had only tinnitus on the right side and the exostoses
is on the left iIAC, thus not responsible for her symptoms.
We present a long term follow-up of 10 years and the patient
remained with no audiovestibular symptoms due to the
exostoses, and no radiological changes in the lesion. These
findings show the very slow growth rate of exostoses, supporting that patients with no or mild symptoms will probably
maintain like that and will not need surgery.
Conflict of Interest
The authors have no conflicts of interest to declare.
References
1. Baik FM, Nguyen L, Doherty JK, Harris JP, Mafee MF, Nguyen QT.
Comparative case series of exostoses and osteomas of the internal auditory canal. Ann Otol Rhinol Laryngol. 2011;120:255---60.
2. Liétin B, Bascoul A, Gabrillargues J, Crestani S, Avan P, Mom T,
et al. Osteoma of the internal auditory canal. Eur Ann Otorhinolaryngol Head Neck Dis. 2010;127:15---9.
3. Gerganov VM, Samii A, Paterno V, Stan AC, Samii M. Bilateral
osteomas arising from the internal auditory canal: case report.
Neurosurgery. 2008;62:E528---9.
4. Ciorba C, Aimoni C, Bianchini M, Borrelli F, Calzolari AM. Bilateral
osseous stenosis of the internal auditory canal: case report. Acta
Otorhinolaryngol Ital. 2011;31:177---80.
5. Davis TC, Thedinger BA, Greene GM. Osteomas of the internal
auditory canal: a report of two cases. Am J Otol. 2000;21:852---6.
6. Wright A, Corbrigde R, Bradford R. Osteoma of the internal auditory canal. Br J Neurosurg. 1996;10:503---6.
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