Vol.2, No.8, 479-483 (2013) Case Reports in Clinical Medicine
Non-echo-planar diffusion-weighted MRI in
cholesteatoma: One typical case, one atypical case
and one rare false positive finding
Martin W. Huellner1*, Eva Novoa2, Manfred Kessler1, Thomas C. Treumann1,
Thomas E. Linder2
1Department of Radiology and Nuclear Medicine, Lucerne Cantonal Hospital, Lucerne, Switzerland;
*Corresponding Author: martin.huellner@usz.ch
2Department of Otorhinolaryngology, Head and Neck Surgery, Lucerne Cantonal Hospital, Lucerne, Switzerland
Received 20 September 2013; revised 20 October 2013; accepted 3 November 2013
Copyright © 2013 Martin W. Huellner et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
We present two cases of cholesteato ma and one
false positive finding in non-EP DW MRI in order
to highlight the differential diagnosis in imaging
and emphasize the need to discuss the findings
with the otologic surgeon. The first case dem-
onstrates different MRI signal patterns encoun-
tered in a patient with cholesteatoma. The sec-
ond report is a rare case of supralabyrinthine
cholesteatoma with atypical clinical presenta-
tion. The third case presents a rare but impor-
tant false positive finding in non-EP DW MRI.
Clinical and imaging findings are discussed
taking into account the current literature.
Keywords: Cholesteatoma; Non-EP DW MRI;
Diffusion-Weighted Imaging
A simple definition of cholesteatoma is “wrong skin at
the wrong place with retention of keratin”. The expan-
sive characteristics of the keratinizing squamous epithe-
lium lead to sharp bony erosions that are easily appreci-
ated on computed tomography (CT) scans. However, CT
cannot confirm the true presence of a cholesteatoma
mass since it differentiates poorly between soft tissue
lesions. Recently, non-echo planar diffusion-weighted
MR imaging (non-EP DW MRI) has gained much atten-
tion due to its short acquisition time and high sensitivity
and specificity for detecting even small cholesteatomas
of 2 - 3 mm in size [1]. Whereas this fast sequence may
be sufficient to screen for residual cholesteatoma in canal
wall-up procedures, we encourage using additional T2-
and T1-weighted sequences in cases of primary diagn osis
of a soft tissue lesion within the temporal bone. We pre-
sent three cases to highlight the differential diagnosis in
imaging and emphasize the need to discuss the findings
with the otologic surgeon.
2.1. Case 1
A 32-year-old male patient presented with a history of
ear pain and recurrent hearing loss on the left side for 2
months. Ten years ago, a pathological otoscopy was re-
ported by a general physician, but no further follow-up
was recommended. At present, a polyp and a grey mass
behind an epitympanic retraction pocket were observed.
Audiometry revealed an air-bone gap of 10 - 25 dB. A
primary acquired epitympanic cholesteatoma was sus-
pected and its extent had to be assessed.
CT scans of the temporal bone revealed subtotal oblit-
eration of the left middle ear and partial obliteration of
the antral mastoidal cells (Figure 1(a)). The ossicle chain
was embedded into the opacity. Bony erosion was sus-
pected. MRI work-up provided further differentiation of
the soft tissue mass in the midd le ear. Within the mass, a
bright signal spot on non-EP DWI (Figure 1(b)) was
interpreted as cholesteatoma. The non-EP DWI sequence
was correlated with a heavily T2-weighted transverse
CISS (constructive interference in steady state) sequence.
The cholesteatoma proved to be the tissue lateral to the
ossicles and in the attic and did not enh ance contrast me-
dium on a T1-weighted delayed post-gadolinium se-
quence (Figure 1(c)). In contrast, the tissue medial to the
ossicles and lateral to the promontory showed distinct
contrast enhancement in the absence of diffusion restric-
tion, strongly suggestive of inflammatory tissue. The
Copyright © 2013 SciRes. OPEN ACCESS
M. W. Huellner et al. / Case Reports in Clinical Medicine 2 (2013) 479-483
Figure 1. (a) NECT (coronal reformat, W/C 3500/600, 250
mAs, voxel size 0.6 × 1 × 1 mm): Ossicle chain embedded in
soft tissue (arrow) and partial obliteration of the antral mas-
toidal cells (arrow head); (b) Non-EP DWI (coronal, b-value:
1000s/mm2, voxel size 1.5 × 1.1 × 3 mm, TR 2000 ms, TE 107
ms): Bright signal spot in the left middle ear suggestive for
cholesteatoma (arrow); (c) Contrast-enhanced T1w with fat
saturation (coronal, voxel size 1.0 × 0.8 × 2.0 mm, TR 533ms,
TE 13 ms, gadolinium-DTPA): Non-enhancing cholesteatoma
lateral to the ossicles (arrow). Enhancing inflammatory tissue
medial to the ossicles (arrow head). Fluid retention in mastoid
cells (white arrow); (d) Intraoperative view of the cholestea-
toma (black arrow) obliterating the mastoidal antrum. A cho-
lesterol granuloma (white arrow) is identified just below. EA:
external auditory canal, PW: posterior wall (black arrow head),
TT: tegmen tympa n i.
mastoidal cells were obliterated and sh owed bright signal
on T2w without contrast enhancement, corresponding to
fluid retention. The findings were confirmed surgically. A
closed mastoido-epitympanectomy (MET) with canal-,
myringo- and ossiculoplasty was performed and the cho-
lesteatoma was completely removed (Figure 1(d)).
2.2. Case 2
A male patient with primary acquired cholesteatoma
underwent open MET at the age of 7. A second look
procedure with ossiculoplasty using a titanium-incus
interposition was performed one year later. Regular fol-
low-up examinations revealed a dry open cavity without
clinical suspicion of recurrent cholesteatoma. At the age
of 14, he presented with an acute facial paresis on the left
side, rapidly progressing to an almost complete paralysis
(Fisch score 15, House-Brackmann score V). Suspecting
acute Bell’s palsy, a seven days trial of 100 mg predni-
solone per day and 1 g valacyclovir tid were given, with
minimal improvement in facial function.
CT scans of the temporal bone showed sof t tissue den-
sities within an osteolysis in the apex of the left temporal
bone, as well as in the widened knee of the facial canal
(Figure 2(a)). Corresponding non-EP DWI and T2-
weighted sequences showed a bright spot in the apex of
the temporal bone, and a smaller, less bright spot in the
facial knee (Figure 2(b)), suspicious of a supralabyrin-
thine cholesteatoma with portions in the petrosal apex
and in the facial knee. Thereby, the initial diagnosis of
Bell’s palsy was revised. A combined transtemporal-
transmastoidal approach with revision of the open MET
and complete removal of the cholesteatoma, which was
located medial to the geniculate ganglion and com-
pressed the labyrinth ine segment of the facial nerve, was
performed 16 days after the onset of the palsy (Figures
2(c) and (d)). The less bright spot in the petrosal apex
turned out to be scar tissue with polypo id swelling. Upon
discharge six days later, facial nerve function had recov-
ered to a House-Brackmann score II and recovered com-
pletely one month later.
2.3. Case 3
A 41 year old male with a history of three previous ear
Figure 2. (a) CT (axial, W/C 3500/600, 250 mAs, voxel size
0.6 × 1 × 1 mm): Osteolysis in the petrous apex (arrow) and
widening of the facial canal (arrowhead). Open cavity after
MET procedure (white asterisk); (b) Non-EP DWI (coronal,
b-value 1000 s/mm2, voxel size 1.5 × 1.1 × 3 mm, TR 2000 ms,
TE 107 ms): Bright signal spot in the petrous apex (arrow) and
smaller, less bright spot in the facial knee (arrow head); (c)
Intraoperative view before removal of the cholesteatoma: the
labyrinthine segment of the facial nerve (arrow head) is com-
pressed by the cholesteatoma (arrow); (d) Intraoperative view
after removal of the cholesteatoma: the labyrinthine segment of
the facial nerve (arrow head).
Copyright © 2013 SciRes. OPEN ACCESS
M. W. Huellner et al. / Case Reports in Clinical Medicine 2 (2013) 479-483 481
surgeries within the last ten years for recurrent cho
lesteatoma, complained of recent pressure on the right
ear. On inspection, a flat white mass was seen covering
the area of the lateral semicircular canal and stapedial
footplate. A residual cholesteatoma within an open cavity
was suspected, and the patient was referred for non-EP
DW MRI. On T2-weighted images and on non-EP DW
images, the mass had a fairly bright signal, suggestive of
recurrent cholesteatoma (Figures 3(c) and (d)). After
MRI, the cavity was extensively cleaned by the otologic
surgeon, and the white incrustation could be removed
from the surface of the lateral semicircular canal and the
Figure 3. (a) T2w (coronal, voxel size 2 × 0.7 × 0.4 mm, TR
4930 ms, TE 124 ms): Bright signal lesion at the medial wall of
the left middle ear (white arrow); (b) Non-EP DWI (coronal,
b-value: 1000 s/mm2, voxel size 1.5 × 1.1 × 3 mm, TR 2000 ms,
TE 107 ms): Bright to intermediate signal lesion at the medial
wall of the left middle ear (arrow); (c) T2w (coronal, voxel size
2 × 0.7 × 0.4 mm, TR 4930 ms, TE 124 ms): Repeat MRI after
removal of the middle ear incrustation: the signal at the middle
ear wall has vanished; (d) Non-EP DWI (coronal, b-value: 1000
s/mm2, voxel size 1.5 × 1.1 × 3 mm, TR 2000 ms, TE 107 ms):
Repeat MRI after removal of the middle ear incrustation: the
signal at the middle ear wall has vanished; (e) View on inspec-
tion a few months after the MRI: Right open mastoid cavity
containing debris and layers of keratin close to the lateral semi-
circular canal and promontory (asterisk). AW: anterior wall of
the external auditory canal, TM: neotympanon.
promontory, lateral to the atelectatic but intact tympanic
membrane. It resembled layers of a keratinous substance
mixed with cerumen. In order to prove that there was no
residual “cholesteatoma”, the MRI was repeated, and, as
was expected, the suspicious signal was gone (Figures
3(c) and (d)). No surgery was performed. On follow-up
clinical investigation one month later, reformation of
cerumen could be seen (Figure 3(e)).
Cholesteatomas are either primary or secondary ac-
quired chronic inflammatory lesions of the middle ear
and mastoid with ingrowth and retention of keratin, or
may present as congenital lesions behind an intact tym-
panic membrane. The destructively growing and expan-
sive keratinizing squamous ep ithelium requires complete
surgical removal. The pathogenesis of cholesteatoma as
well as the incidence and reasons for residual and recur-
rent lesions are still subject of research and debates [2 ].
While CT continues to be the best imaging modality
for preoperative planning [3,4], differentiation of cho-
lesteatoma from fluid or inflammatory tissue is impossi-
ble by tissue density on CT alone. If a mass is found in
the typical location or if bone destruction is present, a
cholesteatoma can be assumed.
MR imaging is superior to CT because of its possibili-
ties to further characterize tissue. For the detection of
cholesteatoma, diffusion weighted imaging (DWI) has
proved to be of great value. In DWI, the intensity of the
magnetic resonance signal depends on the stochastic
Brownian molecular motion, i.e. on the self-diffusion
capability of the excited spins [5]. Water molecules in
cholesteatomas are restricted in their diffusion capability
and contribute to high signal in the images. The standard
technique of DWI is echo-planar (EP), commonly used
for the early detection of cerebral infarction. In the tem-
poral bone however, the value of EP DWI is limited be-
cause of susceptibility artifacts. Here, the appropriate
technique is non-EP DW imaging which has a slightly
longer acquisition time but much less susceptibility arti-
facts and higher signal for cholesteatoma. Non-EP DWI
has a high sensitivity and specificity for cholesteatoma
[5-7]. Occasionally, small keratin pearls of less than 2 - 5
mm may cause false-negative results [3,8,9]. False-posi-
tive results in DWI have been reported for susceptibility
artifacts, scar tissue, bone powder, abscess, and chor-
doma [3,8,10]. To our best knowledge, false-positive re-
sults by keratinous material in non-EP DWI have not
been reported yet.
We showed a valuable example of a false-positive case
in a postoperative patient. In case 3 we assumed that
keratin-like material of a certain chemical constitution
may mimic cholesteatoma by generating a bright signal
in non-EP DWI. To avoid misinterpretation on MRI, we
Copyright © 2013 SciRes. OPEN ACCESS
M. W. Huellner et al. / Case Reports in Clinical Medicine 2 (2013) 479-483
suggest inspecting and cleaning the ear on a short-term
basis before referring the patient to the MRI examination,
especially during follow-up after cholesteatoma surgery
and in patients known to produce retention of dry ceru-
minal wax in their ear canal. A possible group of patients
at risk of such a false-positive finding are those with in-
sufficient or narrow meatoplasties, as the complete radi-
cal cavity can only be overseen poorly, and cleaning of
debris remains a problem. The number and frequency of
second look operations after canal wall-up procedures
has markedly declined after the introduction of non-EP
DW MRI which may be performed 1 - 1½ years after
initial surgery to exclude residual cholesteatoma behind a
reconstructed intact tympanic membrane.
Since DWI images have a low spatial resolution al-
most without anatomic landmarks in the temporal bone, a
high-reso lution T2-weighted sequence is requir ed to cor-
relate DWI findings with the patient’s anatomy. A de-
layed post-gadolinium T1-weighted sequence is not
needed for the detection of cholesteatoma as it does not
yield significant increase in sensitivity or specificity if
obtained in addition to a non-EP DWI sequence [11].
One cannot rely on diffusion signal alone, as false-posi-
tives may occur in certain conditions. In case of a nega-
tive non-EP DWI sequence, an axial T1-weighted se-
quence with and without gadolinium should be obtained
additionally to rule out other pathologies like inflamma-
tion or tumor. The prevalence of both cholesteatoma and
inflammation is seen quite frequently since the cho-
lesteatoma may block the antrum and lead to sterile in-
flammatory changes in the mastoid mucosa, or the cho-
lesteatoma sac may be infected and the miscellaneous
bacterial flora induces an inflammatory response in the
middle ear.
The primary diagnosis of cholesteatoma is based on
the typical otoscopic findings. A high level of suspicion
is required for diagnosis in post-operative patients with
an intact and reconstructed tympanic membrane and ca-
nal wall, in patients with a supra- or infralabyrinthine
extension of the cholesteatoma, being not accessible by
simple otoscopy, and in previously operated ears with a
narrowed canal entrance, complicating the inspection of
the cavity. Radiological imaging helps to confirm the
diagnosis, provides a differential diagnosis and facilitates
surgical planning. Non-EP diffusion MRI can be used to
identify and localize cholesteatoma with high sensitivity
and specificity [5,7]. False-negative results can be ob-
tained in foci smaller than 2 - 5 mm [1,9,1 0]. False-posi-
tive results may be caused by scar tissue [3,8], bone
powder [10] and keratinous material embedded in the
debris of the radical cavity. The imaging gold standard
remains non-EP DWI [1,6,9,12]. Echo-planar DWI should
be abandoned. For anatomic correlation, a high-resolu-
tion T2-weighted image is required. If the non-EP DWI
signal does not suggest cholesteato ma, T1-weighted non-
enhanced and gadolinium-enhanced sequences should be
added to differentiate inflammatory tissue or tumor from
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AW Anterior wall
CISS Constructive interference in steady state
CT Computed tomography
DTPA Diethylenetriaminepentaacetate
DWI Diffusion-weighted imaging
EA External auditory canal
MET Mastoido-epitympanectomy
MR Magnetic resonance
NECT Non-enhanced computed tomography
Non-EP DW MRI Non-echo planar diffusion-weighted magnetic resonance imaging
PW Posterior wall
T1w T1-weighted
T2w T2-weighted
TE Time to echo
TM Neotympanon
TR Time to repeat
TT Tegmen tympani
W/C Width/center