Cholesteatoma is a non-neoplastic keratinizing squamous epithelial lesion that grows in the middle ear. It has an osteolytic potential due to collagenase production. The document discusses the pathogenesis, classification, imaging features, and complications of cholesteatoma. Key findings on imaging include hyperintensity on diffusion weighted MRI sequences indicating restricted diffusion, which is highly specific for cholesteatoma. Complications include ossicular erosion, facial nerve paralysis, and labyrinthine fistula formation.

1. Dr/ ABD ALLAH NAZEER. MD.
Radiological imaging of cholesteatoma.

2. Cholesteatoma is a proliferation of keratinized, stratified squamous
epithelium in an anomalous location, generally in the middle ear. It has
an osteolytic potential, which may be explained by the presence of
collagenase in the lesion periphery, since collagen is the main protein
of the bone tissue.
The term “cholesteatoma” is controversial. According to its literal
transcription, the word derives from “cholesterol” and “tumor”, but in
truth it is an epidermoid cyst. Cholesterol crystals are not observed in the
structure of the lesion which also does not present a tumor-like nature.
PATHOGENESIS:
There are four main theories regarding the origin of acquired
cholesteatomas, namely: retraction, epithelial invasion, middle ear
epithelium metaplasia, and hyperplasia of basal cells. The most widely
accepted theory suggests that cholesteatomas arise from retraction
pockets. If a negative pressure develops in the middle ear (because of
auditory tube dysfunction or infection), the tympanic membrane retracts,
generally in its weakest part - the pars flaccida. Thus, the keratin (which
typically is externally located in relation to the tympanic membrane)
undergoes invagination, remaining in an anomalous position.

3. CLASSIFICATION
Cholesteatomas may be either congenital or acquired.
Congenital cholesteatomas (2%) originate from embryonic epithelial
remains. The patients are born with the tissue in an anomalous position.
There is no history of infection, and the tympanic membrane is intact. The
lesions tend to occur in the anterior tympanic cavity, proximal to the
epitympanum or stapes.
Acquired cholesteatomas are more commonly found (98%), and are
related to a chronic inflammatory process in the middle ear. Its etiology is
associated with the tympanic membrane anatomy which includes three
cell layers, an outer layer in continuity with the mucosa of the external ear
conduct, an inner layer in continuity with the mucosa of the middle ear,
and a middle layer of fibrous tissue that is present only in the pars tensa.
Acquired cholesteatomas may occur in the pars flaccida (82%) and pars
tensa (18%), most commonly arising in the upper portion of the tympanic
membrane pars flaccida, extending towards the Prussak's space, located in
the epitympanum and limited by the pars flaccida, by the lateral ligament
of the malleus, and by the short process of the malleus.

4. Congenital cholesteatoma is a rare entity, arising from aberrant epithelial
remnants left at the time of closure of the neural groove between the third
and fifth week of fetal life. Most often, it has an intradural location, usually in
the cerebellopontine angle and in the middle cranial fossa, or less frequently
(20% of the cases), an extradural location. Extradural congenital
cholesteatoma may be found in the temporal bone, which is the most
frequent site in the skull base. Congenital cholesteatoma of the temporal
bone has to be distinguished from the acquired cholesteatoma, which occur in
the middle ear cavity and rarely extend to the petrous apex. Such a distinction
is made according to clinical criteria: intact tympanic membrane, no history of
aural infection, and no history of tympanic membrane perforation or surgery.
Nonspecific clinical presentation of congenital cholesteatoma requires further
diagnostic investigations. Moreover, the discernment of a pathologic process
in the temporal bone area needs evaluation of its extent for surgical
management. Computed tomography (CT) and magnetic resonance (MR)
have improved the diagnosis of temporal bone tumors and are considered to
be the most accurate imaging modalities in the preoperative staging of
temporal bone tumors. The MR appearance of intracranial epidermoid cysts
is well documented; a few reports have focused on MR imaging of temporal
bone congenital cholesteatoma.

8. Cholesteatoma associated with congenital EAC atresia in a 14-year-old girl with membranous atresia of the
right EAC and bony atresia of the left EAC. CT performed in 2006 showed a right EAC mass deep to the
membranous plug. The mass was not visible at Otoscopy. Temporal bone DWI was not available at that time.
(a) CT image of the temporal bone, obtained in 2009, shows growth of the lesion (*) with erosion of the bony
EAC (arrowheads). There is an atretic plate in the left ear (arrow). (b) Axial high b value PROPELLER diffusion-
weighted image clearly shows the cholesteatoma as a hyperintense mass. Surgery demonstrated a
cholesteatoma involving the EAC and tympanic cavity lateral to the malformed ossicular chain.

9. Congenital right cholesteatoma in a 4-year-old boy with recurrent serous otitis. At otoscopy, a white pearly mass was
seen behind an intact eardrum. A congenital cholesteatoma was suspected and confirmed at surgery. (a) Axial high-
resolution CT image shows a soft-tissue mass filling the anterior meso epitympanum, medial to the ossicular chain.
There is minimal erosion and lateral displacement of the mallear head (arrowhead). (b) Axial high b value PROPELLER
diffusion-weighted image shows hyperintensity of the lesion, a finding highly specific for cholesteatoma.

10. Purulent middle ear disease in a 4-year-old boy with incidentally found bilateral mastoid hyperintensity at
DWI.. (a) PROPELLER diffusion-weighted image shows marked bilateral mastoid hyperintensity. (b) ADC
map shows decreased ADC values. Because the possibility of bilateral congenital cholesteatomas could not
be completely excluded, follow-up PROPELLER DWI was performed. It showed disappearance of the
mastoid hyperintensity, a result indicative of the reversible infectious nature of the abnormal findings.

11. HASTE DWI and PROPELLER DWI in detection of cholesteatoma. (a) Coronal HASTE diffusion-weighted image of a 12-
year-old boy shows a small (2-mm) congenital right mesotympanic cholesteatoma (arrow), which was surgically
confirmed. (Courtesy of Bert De Foer, MD, PhD, GZA Hospitals Sint-Augustinus, Wilrijk, Belgium.) (b) Axial PROPELLER
diffusion-weighted image of a 62-year-old woman with clinically suspected right acquired cholesteatoma shows a 2-
mm cholesteatoma (arrow), which was not visible at otoscopy. The lesion was surgically confirmed.

12. Congenital petrous apex cholesteatoma.

13. Acquired cholesteatomas.

15. Stage according to CT findings. (A) Stage I. Cholesteatoma occupies a single quadrant without ossicular
extension. (B) Stage II. Cholesteatoma occupies at least two quadrants without mastoid extension. (C)
Stage III. Cholesteatoma involve the ossicle. (D) Stage IV. Cholesteatoma extends into the mastoid.

18. A-B: CT of the temporal bones. Axial images showed a hypoattenuating and expansive
lesion in the left mastoid process eroding its medial and lateral walls, adjacent to the
left sigmoid sinus. The remaining structures were unremarkable. C: Follow-up coronal
CT image of the left temporal bone did not reveal recurrence and showed a large
surgical cavity in the mastoid process communicating antrum with tympanic cavity.

19. MSCT with coronal multiplanar reconstruction. A: Lateral wall of the attic/intact bone
spur of Chausse (arrow). B:Presence of soft-tissue within the middle ear in association
with erosion of the lateral wall of the attic/ bone spur of Chausse (arrowhead).

20. MSCT with coronal multiplanar reconstruction. A: Soft-tissue occupying the Prussak's space
and the epitympanum, medially displacing the ossicular chain (asterisk). B: Practically
complete obliteration of middle ear by soft-tissue, with ossicular chain demyelination.

21. Cholesteatomas demonstrate high signal intensity (restricted diffusion) on non-echo-planar DWI sequences.

22. Axial MRI, delayed, contrast-enhanced T1-weighted sequence.
Inflammatory tissue/granulation with intense contrast uptake
(asterisk). Noncontrast-enhanced recurrent cholesteatoma (circle).

23. Recurrent cholesteatoma. At left, MRI delayed contrast-enhanced T1-
weighted image: absence of contrast uptake. At right, MRI diffusion-
weighted EPI: hypersignal compatible with diffusion restriction.

24. MSCT with coronal multiplanar reconstruction: nonspecific soft-
tissue within the middle ear. B,C: Restriction on the EPI sequence
(B) and TSE sequence (C), compatible with recurrent cholesteatoma.

25. Axial (A) and Coronal (B) CT images show aggressive soft tissue mass with complete
destruction of the ossicular chain and erosion of tegmen tympani (white arrows) and
scutum (asterisk). Labyrinthine fistula is also demonstrated. (black arrow)

28. (A-D) Cholesteatoma of the EAC: coronal T1W MRI image (A) shows a hypointense lesion (arrow) in the right
temporal bone. Axial STIR MRI image (B) shows a hyperintense lesion (arrow) extending into the mastoid. Diffusion-
weighted (C) and axial apparent diffusion coefficient (ADC) (D) images show restricted diffusion (arrows).

32. Cholesteatoma with lateral displacement of the incus
with erosion of its lenticular process and of the stapes.

33. 75-year old man with known recurrent cholesteatoma. The examination shows a mass with
mixed intensity on sagittal T1 and high intensity on transverse T2 weighted images. It has a
high intensity on diffusion weighted images, which indicates restricted diffusion. (arrows).

36. MR imaging techniques for cholesteatoma imaging in a patient with a left attic acquired cholesteatoma and associated noncholesteatomatous
soft tissue in the middle ear and mastoid. (a, b) Coronal T1-weighted (a) and axial T2-weighted(b) images of the left middle ear cavity show
nonspecific middle ear filling. Although the rounded epitympanic lesion (arrows in a) corresponded to a cholesteatoma, no specific diagnosis
could be made from these images. (c, d) Subsequent delayed postcontrast(c) and PROPELLER diffusion-weighted (d) images show very specific
results, allowing clear differentiation between the cholesteatoma (arrows) and surrounding inflammatory tissue.

37. EPI DWI versus PROPELLER DWI in diagnosis of middle ear cholesteatoma.(b–e) Recurrent 11-mm left cholesteatoma in a 27-year-old woman 5 years
after canal wall up (CWU) tympanoplasty. (b) PROPELLER diffusion-weighted image (b = 0 sec/mm2) shows T2 hyperintensity of the cholesteatoma
(arrows). (c) High b value PROPELLER diffusion-weighted image (b= 800 sec/mm2) shows increased hyperintensity of the cholesteatoma (arrows)

38. Recurrent postsurgical cholesteatoma in a 42-year-old woman with a history of surgery for cholesteatoma
and right peripheral facial palsy. CT showed a soft-tissue mass in the right anterior epitympanic recess. The
mass eroded the bony canal for the tympanic portion of cranial nerve VII as well as the lateral cochlea. (a)
Axial high b value PROPELLER diffusion-weighted image shows a very hyperintense lesion of the temporal
bone (arrows). (b) Coronal high-resolution T2-weighted image shows cochlear involvement by the lesion
(arrowhead). Coronal imaging also aids in lesion localization. The MR imaging findings allowed exclusion of
other possible lesions in this location, such as facial nerve schwannoma or vascular malformation

40. Coexistent cholesteatoma and cholesterol granuloma in a
20-year-old man 9 months after right CWU tympanoplasty.
Axial PROPELLER diffusion-weighted image (b = 800
sec/mm2 ) (a), corresponding ADC map (b), and axial T1-
weighted fat-saturated image (c) show a residual
cholesteatoma (arrow) with the typical features of
hyperintensity on the high b value image and a low ADC
value. Its hyperintensity on the T1-weighted image is an
atypical feature that resembles the findings of so-called
intracranial white epidermoid cysts. The adjacent
posteriorly located cholesterol granuloma (arrowhead) is
not as hyperintense on the high b value image, with a high
ADC value and hyperintensity on the T1-weighted image.
Both lesions were surgically confirmed.

41. Right side mastoid show an expansile T2 hyper intense soft tissue with restricted diffusion on DWI which is
characteristic of a Cholesteatoma. There is an obvious erosion and destruction of tegmen and dural plate
with adjacent focal vasogenic edema in right cerebellar hemisphere. Opposite mastoid also show similar
but smaller lesion. Imaging diagnosis : Bilateral Cholesteatoma with typical restricted diffusion.

42. 10-year-old boy with a micro-otoscopy suspicion of an attical cholesteatoma.

43. COMPLICATIONS
Ossicular chain osteolysis - It is a frequent complication and leads to transmission deafness. It
occurs in 75% of pars flaccida cholesteatomas, and in up to 90% of pars tensa cholesteatomas.
Long apophysis of the incus, because of its limited ligament support and poor blood supply, is
the most affected ossicular chain segment (87% of cases). The stapes should also be carefully
evaluated, since it is compromised in 21% of cases. Amputation of hammer head and body of the
incus occurs in very advanced lesions, particularly those occurring in the Prussak's space. The
comparison with the contralateral ossicles is essential in the diagnosis of very subtle erosions.
Axial MSCT. Cholesteatomatous lesion in middle ear associated
with ossicular chain osteolysis at left (circle).

44. Erosion of the lateral wall of the attic - The origin of the greatest majority of acquired
cholesteatomas in the pars flaccida of the tympanic membrane with extension through the Prussak's
space justifies, as one of the first tomographic findings, the destruction of the bone spur of Chausses
located in the junction of the lateral wall of the attic with the wall of the external auditory canal.
MSCT with coronal multiplanar reconstruction. A: Lateral wall of the attic/intact bone
spur of Chausse (arrow). B:Presence of soft-tissue within the middle ear in association
with erosion of the lateral wall of the attic/ bone spur of Chausse (arrowhead).

45. Tympanic tegmen lysis - Bone dehiscence with risk for development of
meningoencephaloceles and epidural invasion by cholesteatoma, increasing the
potential for development of meningitis, cerebritis or abscess. MRI is recommended to
evaluate such complications. A comparison with the contralateral tympanic tegmen
should be carried out, since sometimes the bone thickness is already much reduced.
MSCT with coronal multiplanar reconstruction: Thinning with bone destruction of the tympanic
tegmen (oblique arrow) in association with labyrinth fistula (hollow arrow). B: Coronal MRI:
extension of encephalic tissue into the middle ear through tympanic tegmen dehiscence (asterisk).

46. Lysis of facial nerve canal - The facial nerve canal may be eroded and the function of
the nerve can be spared. Facial palsy occurs in approximately 1% to 4% of patients with
cholesteatoma. The most common site of facial nerve compression is the tympanic
segment, which is located inferiorly to the lateral semicircular canal and above the oval
window. The tympanic segment of the facial nerve may be covered by a very thin bone
layer or may be an open canal with the nerve exposed to the middle ear.
MSCT with coronal multiplanar reconstruction. Bone lysis of the facial nerve tympanic segment (arrow).

47. Labyrinth fistula - Potentially severe complication from cholesteatoma, with incidence of 5%
to 10%. The lateral semicircular canal is the most compromised region. The diagnosis of fistula can
be done as the mass is in direct apposition to the labyrinth lumen. Complications originated from the
development of fistulas include neurosensory deafness, dizziness, tinnitus and labyrinthitis.
Cholesteatoma with labyrinth fistula.

48. Others - Mastoiditis, either with or without osteitis; extension to the external
auditory canal; Bezold abscess (abscess caused by mastoid cortex rupture and
extension towards soft tissues); intracranial complications: meningitis,
cerebral/cerebellar abscess, subdural empyema and sigmoid sinus thrombophlebitis.
Cholesteatoma with brain abscess.

49. (A) Axial CT images show soft tissue density occupying epitympanum and opening directly to the
external canal (white arrows). Marked destruction of the ossicular chain (asterisk) and irregularity
of tegmen tympani are also noted. (B) Coronal CT images demonstrate marked erosion of the
lateral tympanic wall (white arrows) with direct connection to the external canal (EAC).

50. Thank You.