Dr/ ABD ALLAH NAZEER. MD.

Radiological imaging of cholesteatoma.

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.

CLASSIFICATIONCholesteatomas 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.

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 cystsis well documented; a few reports have focused on MR imaging of temporal bone congenital cholesteatoma.

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.

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.

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.

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.

Congenital petrous apex cholesteatoma.

Acquired cholesteatomas.

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.

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.

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).

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.

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

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

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.

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.

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)

 (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).

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

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).

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.

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)

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

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.

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.

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

COMPLICATIONSOssicular 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).

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).

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).

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).

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.

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.

(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).

Thank You.