Inner ear lipomas are rare benign congenital lesions, most frequently presenting at the internal auditory canal and labirynth. Lipomas of the facial nerve are even less frequent. We present a case of a lipoma involving all internal ear structures and VII nerve canal and extending intracranially and extracranially, presenting with facial palsy and ipsilateral hearing loss. To our knowledge this is the most extensive case of inner ear lipoma described

Conceição, Carla

Diogo, Mariana Cardoso

Sagarribay, Amets

English

Acta Radiológica Portuguesa

ACTA RADIOLÓGICA PORTUGUESA
Maio-Agosto 2016   nº 108   Volume XXVIII   59-61
EXTENSIVE INNER EAR AND FACIAL CANAL LIPOMA - A 
CASE REPORT
EXTENSO LIPOMA DO OUVIDO INTERNO E CANAL DO FACIAL – 
CASO CLÍNICO
Mariana Cardoso Diogo1, Amets Sagarribay2, Carla Conceição1
1Departamento de Neuroradiologia, Centro 
Hospitalar de Lisboa Central, Lisboa
2Serviço de Neurocirurgia, Centro Hospitalar de 
Lisboa Central, Lisboa
Trabalho realizado no Serviço de Radiologia do 
CHLC – Polo Hospital Dona Estefânia
Director de Serviço: Dr João Reis
Directora do polo: Dra Eugénia Soares
Correspondência
Mariana Cardoso Diogo
Departamento de Neurorradiologia 
Hospital de São José
Rua José António Serrano
1150 Lisboa
e-mail:mariana.cardoso.diogo@gmail.com
Recebido a 14/04/2016
Aceite a 24/08/2016
59
Abstract
Inner ear lipomas are rare benign congenital 
lesions, most frequently presenting at the internal 
auditory canal and labirynth. Lipomas of  the 
facial nerve are even less frequent. We present 
a case of  a lipoma involving all internal ear 
structures and VII nerve canal and extending 
intracranially and extracranially, presenting with 
facial palsy and ipsilateral hearing loss. To our 
knowledge this is the most extensive case of  
inner ear lipoma described.
Key-words
Inner ear lipoma; Inner ear lipochoristoma; 
Facial nerve lipoma; Sensory hearing loss; Facial 
nerve palsy.
Resumo
Os lipomas do ouvido interno são lesões 
congénitas benignas raras, localizadas mais 
frequentemente no canal auditivo interno. 
Lipomas do nervo facial são ainda mais raros. 
Apresentamos um caso de lipoma a envolver 
a totalidade das estruturas do ouvido interno, 
canal do nervo facial e com extensão intra- e 
extracraniana, manifestando-se com paresia facial 
e hipoacusia ipsilaterais. Tanto quanto nos foi 
possível averiguar, este é o caso mais extenso de 
lipoma do ouvido interno descrito na literatura.
Palavras-chave
Lipoma do ouvido interno; Coristoma do 
ouvido interno; Lipoma do nervo facial; 
Hipoacusia neuro-sensorial; Paresia facial
Caso Clínico / Radiological Case Report
Introduction
Inner ear lipomas are rare benign congenital lesions, believed 
to derive from the persistence and maldifferentiation of  the 
mesenchymal precursor of  the meninges (mininx primitiva) 
that becomes trapped inside the otic capsule during early 
embryonic development1. In most cases they present extension 
along the vestibulocochlear nerve to the internal auditory 
canal, with some presenting with cerebellopontine angle (CPA) 
masses. Lipomas of  the facial nerve are even less frequent 
with only a few cases published. We present a case of  a lipoma 
involving all internal ear structures and VII nerve canal and 
extending intracranially and extracranially. To our knowledge 
this is the most extensive case of  inner ear lipoma described.
Institutional board review was waived for a single retrospective 
case report. 
Acknowledgements
The authors thank Dr Luís Távora for his 
contribution in the initial diagnosis of  the 
patient.
Clinical Case
A five-month-old female patient was referred to our center 
due to congenital left peripheral facial nerve palsy and 
ipsilateral moderate to severe sensorineural hearing loss 
(SNHL). She had passed the newborn hearing screening 
test. Her development was otherwise unremarkable for her 
age and she presented no other neurological deficits.
Computed tomography (CT) was initially performed, 
followed by magnetic resonance imaging (MRI). On CT 
a dilatation of  the facial nerve canal, particularly of  the 
geniculate ganglion region and the third (mastoid) portion 
was identified. The internal auditory canal (IAC) was 
mildly abnormal (Figure 1B), with a large falciforme crest. 
Round well-marginated low-density masses were identified 
emerging from the porus acusticus into the CPA, and in 
the temporal fossa (figure 2), adjacent to the dehiscent 
geniculate ganglion region, and also extracranially, 
protruding from the stylomastoid canal (Figure 3). A small 
mass could also be identified protruding in the posterior 
60
wall of  the tympanic cavity (Figure 1C). An abnormal 
density (-112 HU) was identifiable in the vestibule, facial 
canal and IAC, in apparent continuity with the intracranial 
and extracranial masses. The lesion was better depicted on 
MRI (Figures 3, 4), and shown to further involve the cochlea 
and semicircular canals. It presented high signal intensity (SI) 
on T1 and T2-weighted images, without enhancement after 
gadolinium injection. A lipomatous lesion was suspected, 
but given the exuberance and size of  the mass, a neoplastic 
lesion could not be completely excluded and the middle fossa 
component was surgically excised. Histopathological analysis 
was compatible with a lipoma. 
Follow-up exams were performed annually for two years and 
biannually thereafter. The lesion remained imagiologic and 
clinically stable for over 6 years, with the patient maintaining 
a normal development. Given this stability, she currently has 
no indication for further imaging studies in the absence of  
new symptoms.
Discussion
We present the CT and MR imaging findings in a child with 
a lipoma involving the IAC, inner ear structures and facial 
canal, protruding intracranially to the CPA and middle cranial 
fossa, and extracranially through the stylomastoid foramen. 
Inner ear lipoma is a rare congenital lesion, often associated 
with a simultaneous lipoma in the cerebellopontine angle2. 
They are believed to arise from the persistence  of  the mininx 
primitiva, with its incorporation into the developing otocyst, 
as it invaginates or folds in the early stages of  embryonic 
development1-3. 
On CT lipomas have a density in the range of  fat (around 
-100 HU). They may enlarge and slightly remodel the bone, 
but show no infiltrative or aggressive characteristics, and 
clear cortical margins of  surrounding bone should be seen 
at all times. On MR they present as non-enhancing lesions 
that follow the signal intensity of  fat tissue in all sequences, 
suppressing completely with fat saturation. In the inner ear, 
they might be overlooked on T2W images as their typical 
high signal can mimic that of  endolymph/perilymph (Figure 
4B). In smaller (focal) inner ear lipomas main differential 
diagnosis are intralabyrinthine schwannomas, that may also 
present in the CPA – it is essential to perform T1 sequences 
before gadolinium, to avoid mistaking T1 high signal intensity 
(SI) with contrast enhancement. A more diffuse T1 high SI 
Figure 1 –  Axial CT scan, bone window, at the level of  the cochleae (A), 
depicting a relatively normal and symmetrical anatomy; left ear, at the level 
of  the internal ear canal (B), showing an enlarged canal and the proeminente 
falciform crest (red arrow); and at the level of  the epitympanum (C) depicting 
the lipomatous mass extending into the posterior middle ear (white arrow).
Figure 2 -  CT scan performed at 5 months, axial scans in soft tissue (A) 
and bone (B) windows depicting the temporal fossa mass (white arrow), 
extending directly from the inner ear structures. Notice the hypodensity 
corresponding to fat density.
Figure 3 – Coronal T1 image showing the extension into the cerebellopontine 
angle (red arrow), the 3rd mastoid portion of  the facial canal (dashed arrow), 
extending to the extracranial space inferiorly (white arrow)
Figure 4 – Axial MRI images at the level of  the cochleae. On T1-weighted 
image (A) the high signal intensity of  all inner ear structures (red arrow) can 
be identified and is very distinct from the contralateral (normal) side (white 
arrow). On the T2-weighted image (B) signal intensity of  fat is similar to the 
endolymph and perilymph and the abnormalities are not as clear.
A
B C
A
B
A B
61
of  the inner ear structures can also be present in cases of  
haemorrhage or very high protein content. FS sequences are 
essential in these cases.
In contrast to intracranial lipomas, which are usually 
asymptomatic, most patients with inner ear lesions present 
with SNHL1. Facial palsy is observed in only 5% of  
patients2. The exact etiology of  the SNHL cannot be entirely 
explained by the mass effect of  the tumor on the VIII nerve, 
as a significant percentage of  patients develop progressive 
hearing loss after birth, while lipoma size remains stable. 
It has been proposed that this may be secondary to toxic 
effect on cochlear hair cells of  lipid material breakdown 
in the intralabyrinthine space1. Our patient presented with 
peripheral facial palsy and progressive SNHL, probably 
of  mixed origin - nerve compression and infiltration and 
cochlear dysfunction. She exhibited no signs of  vestibular 
dysfunction despite the semicircular canals involvement.
These lesions remain stable throughout life and any change in 
clinical complaints or imaging characteristics should warrant 
an adequate investigation. Otherwise, a follow up exam one 
year after diagnosis, to ensure that there isn’t significant 
change in size, appears to suffice4. There is no described 
advantage in long term radiological follow up.
Surgical intervention in patients with intravestibular lipoma 
is associated with high morbidity and should be avoided, 
making correct imaging diagnosis paramount3,4.
We believe that the intracranial extensions observed in our 
patient’s case are part of  the same lesion, in continuity with 
the VII and VIII cranial nerves through the porus acusticus 
into the CPA, from the geniculate ganglion following the 
GSPN as it enters the middle cranial fossa, and exiting 
the skull base inferiorly with the facial nerve through the 
stylomastoid foramen. The imaging characteristics are 
undoubtedly of  an adipose mass and the stability of  the 
lesion attests to its benignity. The histopathological results 
confirm the diagnosis.
To our knowledge there is only one other case of  a lipoma 
involving all structures of  the inner ear reported in English 
literature5. Our report further adds involvement of  the facial 
nerve canal in its entirety and of  the IAC.
In conclusion, inner ear lipoma is a very rare pathology, 
with typical density and signal characteristics on both CT 
and MRI. Knowledge of  this entity is essential to avoid 
unnecessary invasive procedures or imaging follow-ups, even 
when lesions are imagiologically exuberant, such as in the 
case presented.
References
1. Dahlen RT, Johnson CE, Harnsberger HR, et al. CT and MR imaging 
characteristics of  intravestibular lipoma. AJNR Am J Neuroradiol. 
2002;23:1413-7. 
2. Bacciu A, Di Lella F, Ventura E, Pasanisi E, Russo A, Sanna M. Lipomas 
of  the Internal Auditory Canal and Cerebellopontine Angle. Ann Otol 
Rhinol Laryngol. 2014;123:58-64.
3. Buyukkaya R, Buyukkaya A, Ozturk B, Yaman H, Belada A. CT and MR 
Imaging Characteristics of  Intravestibular and Cerebellopontine Angle 
Lipoma. Iran J Radiol. 2014;11:e11320.
4. Kontorinis G, Freeman SR, Potter G, Rutherford SA, SiripurapuRekha, 
King AT, et al. Management of  Cerebellopontine Angle Lipomas: Need for 
Long-Term Radiologic Surveillance? OTOL Neurotol. 2014;35:e163-8
5. Karadeli E, Meltem E, Ulu K. Inner ear lipoma. Diagn Interv Radiol. 
2010;16:24–6.


Extenso lipoma do ouvido interno e canal do facial

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Extenso lipoma do ouvido interno e canal do facial

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