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Temporal Bone, Acquired Cholesteatoma
Updated: May 1, 2007
Introduction
Background
A cholesteatoma consists of an accumulation of desquamated keratin epithelium in the middle ear cleft or any other pneumatized portion of the temporal bone. The envelope of a cholesteatoma is termed a matrix, and desquamated keratin is shed continually by the matrix and forms the central mass of the cholesteatoma, similar to the layers of an onion. The term cholesteatoma is a misnomer, since the entity does not contain cholesterol.
Pathophysiology
Cholesteatomas are classified as congenital or acquired, and acquired cholesteatomas are subdivided into primary (attic retraction) or secondary categories.
Derlacki defines congenital cholesteatomas as an embryonic remainder of epithelial tissue in the ear, without either tympanic membrane perforation or history of infection.1
Primary acquired cholesteatomas appear as a defect of variable size adjacent to the posterosuperior portion of the tympanic membrane (pars flaccida). The center of the defect contains keratin debris. In secondary acquired cholesteatomas, the keratin epithelium has migrated through a tympanic membrane perforation.
Cholesteatomas may be limited to the external auditory canal. They present as limited lesions lateral to the normal tympanic membrane; they erode the tympanic bone in older patients with otorrhea and no hearing loss. Cholesteatoma should be differentiated from keratosis obturans, which is of unknown etiology and is characterized by a large amount of cerumen and keratin filling the external ear canal; keratosis obturans produces otalgia, hearing loss, and otorrhea, usually with bilateral involvement and erosion of the external canal in younger patients.
Cholesteatoma can erode bone. Multinucleated osteoclasts within the subepithelial matrix release acid phosphatase, collagenase, and other proteolytic enzymes. The osteoclast may be activated further by infection, water contamination, pressure, and Langerhans cells.
Frequency
United States
The prevalence of acquired cholesteatoma in the United States is unknown. Congenital cholesteatoma is extremely rare.
Mortality/Morbidity
As cholesteatomas expand and become infected, they cause ossicular chain destruction, exposure of the membranous labyrinth, exposure of the facial nerve and dura, and infection of the mastoid and intracranial spaces.
Intratemporal and intracranial infections occur in less than 1% of all cholesteatomas because of the widespread use of antibiotics and the tendency to operate earlier. Patients who develop headaches on the same side in which a cholesteatoma has developed should undergo computed tomography (CT) scanning to exclude an impending intracranial complication.
- Hearing loss - Ossicular chain erosion occurs in 30% of patients with cholesteatoma. Attic cholesteatomas involve the head of the malleus and body of the incus early.
- Labyrinthine fistula - A labyrinthine fistula may be found in as many as 10% of patients with long-standing cholesteatoma or in revision cases. A fistula is suggested in patients with chronic ear disease who have sensorineural hearing loss and/or vertigo induced by noise or pressure changes in the middle ear. Suppurative labyrinthitis with complete hearing loss and vestibular function may occur secondary to a fistula from a cholesteatoma. High-resolution thin-section CT scanning of the temporal bone may reveal a fistula of the semicircular canals or the basal turn of the cochlea. Fistulae of the horizontal semicircular canal are most common.
- Facial paralysis - Facial paralysis in patients with a cholesteatoma may develop acutely, secondary to infection, or slowly, as a result of chronic expansion. High-resolution thin-section CT images with both axial and coronal scanning localize the involvement. Topographic testing may confirm the site of injury. The most common site of paralysis is the geniculate ganglion.
Race
Racial prevalence has not been proven.
Sex
In congenital cholesteatoma, the male-to-female ratio is 3:1.
Age
Levenson et al have established an average age at presentation of 4.5 years for patients with congenital cholesteatoma.2
Anatomy
Pathologic anatomy
Acquired cholesteatoma appears similar to a gray or yellowish pearl and is perfectly defined in the middle-ear cavity. In almost every patient, a lesion of the ossicular chain and of the scutum (lateral wall of the attic) is noted.
Surgical anatomy
The middle ear is divided into 3 compartments as follows:
- The mesotympanum is the portion of the middle ear that is between the horizontal plane traced at the superior and inferior border of the pars tensa. It contains the stapes, the manubrium of the malleus, the long process of the incus, and the oval and round windows.
- The epitympanum is the portion of the middle ear that is above the level of the short process of the malleus. It contains the head of the malleus, the body of the incus, mucosal folds, and ligaments.
- The hypotympanum is the portion that is below the floor of the external ear canal.
According to Jackler, the most common locations of origin of acquired cholesteatomas in order of descending frequency are the posterior epitympanum, posterior mesotympanum, and anterior epitympanum.3
Middle-ear pouches and spaces are related to the tympanic membrane and the cholesteatoma. The Prussak space is also termed the anterior recess of the tympanic membrane and is located between the pars flaccida and the neck of the malleus. The lateral mallear fold is the superior limit and is attached to the bony margin of the notch of Rivinus and the lateral process of the malleus as the inferior limit.
The posterior von Troeltsch space is also termed the posterior recess of the tympanic membrane; it is a pouch lying between the tympanic membrane and the posterior mallear fold. The chorda tympani nerve lies in the free margin of the posterior mallear fold. The anterior pouch of von Troeltsch lies between the portion of the drumhead anterior to the malleus handle and the anterior mallear fold.
Four sinuses are found at the posterior tympanic wall (ie, the sinus tympani, the lateral tympanic sinus, the posterior tympanic sinus, and the facial sinus). In chronic middle-ear disorders, the facial sinus always is found to contain pathologic tissue.
Presentation
The diagnosis of acquired cholesteatoma is made after a complete history is elicited and a physical examination is performed.
Symptoms may vary. Some patients with cholesteatomas are asymptomatic, while other patients present with long-standing, malodorous otorrhea and conductive hearing loss. Some patients ignore the disease until impending complications develop, which are characterized by the onset of otalgia, vertigo, headache, facial nerve paresis, or meningitis.
The treatment of acquired temporal-bone cholesteatoma is surgical. The 2 principal surgical techniques used are called canal wall up and canal wall down; the terms relate to the treatment of the posterior external auditory canal wall. The surgeon must determine the best procedure based on local factors, such as the extent of disease or the presence of complication, and on general factors, such as the medical condition of the patient and the surgeon's own skill and experience.
Preferred Examination
Otoscopic examination is the most important diagnostic technique. In primary acquired cholesteatoma, a retraction pouch is seen in the attic and contains keratin debris. In secondary acquired cholesteatoma, a tympanic membrane perforation is seen in which the epithelium has migrated through the borders and already has reached the middle-ear space. In an infected cholesteatoma, moderate fetid secretions with osteitis and granulation tissue are seen; these can be in the form of inflammatory aural polyps.
Conventional temporal-bone projections and special imaging procedures, such as high-resolution CT scanning and magnetic resonance imaging (MRI), are employed to complement physical examination and to determine the extent of the disease process, being utilized preoperatively to plan surgical treatment. CT scanning and MRI are useful when revision surgery is performed.
High-resolution CT scanning in the axial and coronal planes is the imaging procedure of choice in the diagnosis of temporal-bone cholesteatomas.
Limitations of Techniques
Basically, conventional radiographic studies exhibit great limitations because of the complex anatomy of the temporal bone and the subtle changes induced by small cholesteatomas.
CT scans also have limitations. With CT, it is difficult to differentiate a cholesteatoma from granulation tissue, pus, and fluid, which are present in chronic otitis media without the presence of a cholesteatoma.
The principal limitation of MRI is the lack of bone conspicuity and detail due to the lack of mobile protons in dense cortical bone and signal void experienced when a radiofrequency pulse is applied. Because the major changes induced by a cholesteatoma in the temporal bone are produced within the bony framework, MRI has only a supportive role in the evaluation of subjacent extension of disease outside the confines of the temporal bone, intracranial extension, or rare vascular insult that may occur in large, chronic, or relapsing cases.
The high cost of advanced technology imaging presents a major limitation in public institutions and developing countries.
Differential Diagnoses
Glomus Tumor (Head and Neck)
Temporal Bone, Fractures
Other Problems to Be Considered
Middle ear - Tympanic membrane perforation and benign tumor
Inner ear - Presbycusis and evaluation for dizziness
Aural atresia
Otitis media - Pediatric cases and complications
Kartagener syndrome
Patulous eustachian tube
Mastoiditis
Skull base - Petrous apex infection
Residual and relapsing cholesteatomas must be differentiated following surgery. Relapsing cholesteatoma is defined as a pathologic mass that reappears from the keratin epithelium that was not removed during surgery. Recurrent cholesteatoma appears because of the incapacity of the eustachian tube to ventilate the temporal bone. Austin (personal communication) has proposed that the term relapsing cholesteatoma be used for both forms because of the difficulty in differentiating the 2 cholesteatomas based on clinical examination. This would allow uniform use of the term in the literature. CT scanning is one of the best tools for making the diagnosis of relapsing cholesteatoma. CT imaging is convenient 18-24 months after a canal-wall-up procedure (conservative) is performed. CT scanning uses axial and coronal views without the intravenous administration of contrast material.
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References
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Further Reading
Keywords
keratoma, congenital cholesteatoma, primary acquired cholesteatoma
