Chapter 50. Cholesteatoma

• Squamous epithelium in the middle ear or mastoid
• Otorrhea and conductive hearing loss
• Retraction of the tympanic membrane with a squamous debris collection or a whitish mass behind an intact tympanic membrane
• Testing includes computed tomography (CT) scanning, which can be useful in delineating disease extent but is not critical to making a diagnosis in most cases

Acquired Cholesteatoma

Cholesteatoma is the presence of squamous epithelium in the middle ear, mastoid, or epitympanum. The most common form of cholesteatoma is the acquired variety, which is classified as primary and secondary acquired cholesteatoma. Primary acquired cholesteatoma is the most common of these types and forms as a retraction of the tympanic membrane. In most cases, the retraction occurs in the pars flaccida, although pars tensa retractions can also occur (Figure 50–1). Secondary acquired cholesteatoma forms as a result of either squamous epithelial migration from the tympanic membrane or implantation of squamous epithelium into the middle ear during surgery, such as ventilation tube placement or tympanoplasty.

Congenital Cholesteatoma

Cholesteatomas that occur without tympanic membrane retraction or implantation of squamous epithelial material are considered to be congenital in origin. This comprises a minority of cholesteatoma cases. It is classically defined as an embryonic rest of epithelial tissue in the ear without tympanic membrane perforation and without a history of ear infection. This definition has been modified in recent years, but essentially it is a condition typically seen in young children without evidence of the acquired type of cholesteatoma.

The pathogenesis of primary acquired cholesteatoma remains unclear. Factors that appear to be associated with formation of cholesteatoma retractions of the tympanic membrane include poor eustachian tube function and chronic inflammation of the middle ear, as in chronic otitis media. In theory, chronic negative middle ear pressure leads to retractions of the structurally weakest area of the tympanic membrane, the pars flaccida. Once the retractions form, the normal migratory pattern of the squamous epithelium is disrupted, resulting in the accumulation of keratin debris in the cholesteatoma sac. Chronic infection and inflammation ensue, leading to biochemical changes in the local environment that foster the further growth and migration of the squamous epithelium and increased osteoclastic activity, resulting in bone resorption. The local inflammatory response further inhibits eustachian tube function, increases mucosal edema and mucous secretion, and disrupts the drainage pathways of the temporal bone. This environment also fosters the growth of bacteria, including Pseudomonas aeruginosa, Streptococcus, Staphylococcus, Proteus, Enterobacter, and anaerobes, which increase the host's inflammatory response and continue the cycle. It is not understood why only a small percentage of patients with poor eustachian tube function develop cholesteatoma and why some patients form pars tensa retractions rather than the more common pars flaccida retraction.

The pathogenesis of congenital cholesteatoma is unclear, but the most prevalent theory is the failure of involution of the epithelioid formation in the middle ear during fetal development. Other theories include metaplasia of the middle ear mucosa and, more recently, direct microretractions of the tympanic membrane near the malleus long process that are self-limited, but leave squamous epithelial rests in the middle ear.

There are currently no known methods by which congenital cholesteatoma can be prevented. Secondary acquired cholesteatomas are often iatrogenic and therefore could theoretically be prevented if the surgeon takes all steps possible to prevent implantation of squamous epithelium into the middle ear.

Although the pathogenesis of primary acquired cholesteatoma is not clearly understood, if it is assumed that eustachian tube dysfunction is required for its formation, restoring eustachian tube function should help prevent the formation of this type of cholesteatoma. Unfortunately, there is no way to correct eustachian tube function directly. However, providing secondary ventilation to the middle ear space can reduce the complications related to poor eustachian tube function. This can be accomplished by inserting a ventilating tube. If early progressive tympanic membrane retractions are detected, this intervention could potentially prevent future progression of the disease to cholesteatoma. In addition, the successful control of infection and the inflammatory state of the middle ear, followed by regular débridement of the cholesteatoma sac in an office setting, can prevent future progression of the cholesteatoma in some cases.

Symptoms and Signs

Patients with acquired cholesteatomas typically present with recurrent or persistent purulent otorrhea and hearing loss. Tinnitus is also common. However, some patients with cholesteatoma may not develop otorrhea for a long period of time. In rare cases, vertigo or dysequilibrium can result from the inflammatory process in the middle ear or, in rare cases, from direct labyrinthine erosion by cholesteatoma. Facial nerve twitching, palsy, or paralysis can also result from the inflammatory process or from mechanical compression of the nerve.

Physical findings are usually diagnostic in cases of acquired cholesteatoma. In primary acquired cholesteatoma, there will be a retraction of the pars flaccida in most cases, and less commonly in the pars tensa (Figure 50–2). Both types of retractions contain a matrix of squamous epithelium, which may or may not be visible, and often keratin debris. Other typical findings include purulent otorrhea, polyps and granulation tissue, and ossicular erosion. In secondary acquired cholesteatoma, the findings depend on the cause. If the cholesteatoma developed from a tympanic membrane perforation, the squamous epithelial matrix, keratin debris, or both are usually visible through the perforation. If the cholesteatoma developed from either an implantation of squamous epithelium during surgery or a perforation that has closed, the tympanic membrane may in fact appear relatively normal. Once the middle ear cholesteatoma has enlarged to a sufficient size, it becomes visible behind the tympanic membrane. In patients whose tympanic membrane is opaque, further studies, such as imaging, may be required.

Congenital cholesteatomas are usually asymptomatic until the mass grows to a sufficient size that the ossicular chain function becomes disrupted and hearing loss develops. In many cases, the cholesteatoma is noted on the routine ear examination of an asymptomatic child.

In all cases, cranial nerve function, especially that of the facial nerve (CN VII), should be examined. In addition, an office evaluation for nystagmus and balance function should be considered in patients who have any evidence of vestibular dysfunction. A fistula test can be performed, but it has a low sensitivity in detecting labyrinthine fistula.

Imaging Studies and Special Tests

CT Scanning

CT can be performed to delineate the extent of disease. Bone window axial and coronal cuts of 1.5-mm slices or less are ideal. It should be understood that a CT scan usually cannot make a definitive diagnosis regarding the nature of any existing temporal bone disease. CT findings that are suggestive of the presence of cholesteatoma include the erosion of bone, most commonly the scutum and ossicular chain (Figure 50–3). The presence of erosion of the labyrinth is highly suggestive of the presence of cholesteatoma, although neoplasms can also cause this finding. CT scanning cannot differentiate between fluid and tissue and, in particular, cannot distinguish between tissue types. The presence of fluid or soft tissue density in the middle ear and mastoid could indicate the presence of mucus, pus, inflammatory tissue such as granulations or polyps, thickened mucosa, cholesteatoma, neoplasm, encephalocele, or other conditions.

CT scans are especially useful in patients with a history suggestive of secondary acquired cholesteatoma in which the middle ear cannot be visualized because the tympanic membrane is opaque. In these cases, the amount of inflammatory tissue may be minimal, and the soft tissue density of the cholesteatoma may be identifiable, thereby aiding in the diagnosis. CT scanning is also useful for delineating the extent of disease in congenital cholesteatoma. This imaging modality can assist the surgeon in determining whether a tympanoplasty alone is adequate for treatment or whether a mastoidectomy will also be needed.

Many surgeons find CT scanning useful in planning any surgical intervention. A CT scan can indicate the presence of low tegmen, anterior sigmoid sinus, labyrinthine erosion, ossicular erosion, and petrous apex involvement, all of which can affect the surgeon's approach to the disease. In some cases, facial nerve dehiscence and tegmen erosion can be detected, but these conditions are more accurately determined at the time of surgery. It should be noted that CT imaging is not a requirement prior to surgical intervention, because most of the relevant information that CT scanning provides becomes apparent at the time of surgery. In fact, many surgeons do not routinely obtain imaging unless there are specific indications, such as revision surgery, suspicion of labyrinthine fistula, or the possibility of petrous apex disease.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) can, in theory, differentiate between tissue types and may therefore aid in the diagnosis of cholesteatoma. In practice, the small confines of the ear and mastoid, and the frequent presence of inflammatory disease, make determination of tissue characteristics difficult using the current technology. However, MRI is useful if a neoplasm or an encephalocele is suspected.

Audiometry

An audiogram should be obtained in all cases. Patients with cholesteatoma usually exhibit various degrees of conductive hearing loss, depending on the status of the ear canal, the tympanic membrane, and the ossicular chain. The presence of an otherwise unexplained sensorineural hearing loss should alert the surgeon to the possibility of a labyrinthine fistula, although in most cases, this hearing loss results from a chronic or recurrent inflammatory process.

In most cases of primary acquired cholesteatoma, the diagnosis is quite clear after obtaining the history and performing a physical examination. However, diagnostic considerations in patients with recurrent or persistent otorrhea include chronic otitis media without cholesteatoma; otitis externa; malignant external otitis; neoplasms such as squamous cell carcinoma of the ear or other rare tumors, such as adenomas; adenocarcinoma; adenoid cystic carcinoma; and cerebrospinal fluid otorrhea, such as from an encephalocele. If there is any doubt regarding the diagnosis, further workup, such as biopsy, laboratory studies, and imaging, should be considered.

The diagnostic considerations for cases in which the tympanic membrane appears intact or even normal, such as in cases of congenital and some cases of secondary acquired cholesteatoma, can be more problematic. In such children who present with conductive hearing loss, diagnostic considerations include congenital malformation of the ossicular chain, the most common of which is stapes fixation, or ossicular dysfunction resulting from either previous inflammatory disease of the ear or trauma. In adults presenting with normal tympanic membrane and conductive hearing loss, diagnostic considerations include otosclerosis and ossicular dysfunction resulting from previous inflammatory disease of the ear or trauma. A CT scan can be helpful in obtaining a diagnosis in these cases.

Cholesteatomas result in the continued slow growth of the keratin sac with chronic inflammation and infection in most cases. The major sequelae are bone erosion, which results in erosion of the ossicular chain, and otorrhea. In some cases, cholesteatomas can become complicated over time and result in sensorineural hearing loss, dizziness, facial nerve injury, and suppurative complications such as acute mastoiditis, subperiosteal abscess, sigmoid sinus thrombosis, meningitis, and brain abscess.

Nonsurgical Measures

The initial goal of treatment for cholesteatomas is to reduce the level of the inflammatory and infectious activity in the involved ear. The mainstays of medical treatment are to remove infected debris from the ear canal, keep all water out of the ears to prevent further contamination, and apply ototopical agents that cover the usual bacterial organisms, which include P aeruginosa, streptococci, staphylococci, Proteus, Enterobacter, and anaerobes. Commercially available agents such as ofloxacin or neomycin-polymyxin B are usually adequate. If the middle ear is exposed, there is a theoretical danger of causing ototoxicity with the use of agents such as aminoglycosides. This risk has not been studied adequately but appears to be relatively low in cases of chronic inflammation; however, it may be in the patient's best interest to avoid ototoxic agents and instead use agents such as ofloxacin.

Some physicians favor the additional use of topical steroid agents to reduce both the level of inflammation and the volume of any inflammatory tissues that are present. The efficacy of this treatment modality has not been studied adequately, but in theory, the anti-inflammatory effects could be beneficial. However, it is also theoretically possible that steroids may inhibit the local immune responses, allowing progression of the infectious process.

In many cases, the infection fails to subside completely. This situation usually occurs in the presence of a cholesteatoma sac with infected keratin debris that is not effectively treated by any local or systemic agents. However, after surgical treatment, the otorrhea usually resolves.

Surgical Measures

Treatment Goals

The definitive treatment of cholesteatoma should achieve several goals. The primary goal is to create a “dry and safe” ear. Essentially, this means that the processes that are causing bone erosion, chronic inflammation, and infection should be reversed permanently. To achieve this goal, all cholesteatoma matrices must be either removed or exteriorized. Failure to accomplish this usually results in persistent or recurrent disease. If a cholesteatoma matrix is exteriorized, as in cases of canal-wall-down tympanomastoidectomy or atticotomy, the cavity should be designed to be relatively self-cleaning so that it will not be prone to develop chronic otorrhea. A summary of surgical approaches is shown in Table 50–1.

Anatomic Considerations

Cholesteatoma can involve any area of the middle ear, hypotympanum, protympanum, epitympanum, and mastoid. Since most cases of cholesteatoma arise from a retraction of the tympanic membrane, it follows that most cases involve the middle ear space in some form. Pars flaccida retractions are the most common. These cholesteatomas typically invade Prussak's space, which is the area between the pars flaccida laterally and the malleus neck and the lower portion of the head medially. From here, the cholesteatoma can invade the middle ear inferiorly, the attic, and then the mastoid superiorly.

Middle Ear

The most common location of cholesteatoma in the middle ear is in the area around the stapes superstructure and incus long process. This area is usually difficult to dissect because of the presence of the facial nerve and ossicular chain. The facial recess, sinus tympani, and posterior hypotympanum are also areas where the surgeon can easily leave behind cholesteatoma because surgical access to these locations is quite limited (Figure 50–4). The remainder of the mesotympanum is usually accessed without difficulty.

Epitympanum

After the mesotympanum, the epitympanum is the next most common location for cholesteatoma. The ossicular chain usually obstructs adequate visualization in this area, but removal of the incus and malleus head significantly improves the exposure. The area anterior to the malleus head can harbor cholesteatoma that can escape the surgeon's attention unless this area is adequately exposed. In some cases, the tegmen is so inferiorly positioned that access to the epitympanum is not adequate without removing the posterior and superior canal wall.

Mastoid

The mastoid can contain a large amount of cholesteatoma, but access to the mastoid is relatively straightforward using standard otologic techniques (Figure 50–5). In some cases, a very low tegmen and very anterior sigmoid sinus can make the surgical exposure inadequate, in which case the canal wall will need to be removed. Once the horizontal semicircular canal has been identified, the surgeon will become oriented to important structures such as the facial nerve and the remainder of the labyrinth.

Petrous Apex

Occasionally, the cholesteatoma invades the petrous apex through various air cell tracts. These include the subarcuate, retrolabyrinthine, supralabyrinthine, retrofacial, and infralabyrinthine tract. Petrous apex cholesteatomas usually cannot be accessed adequately using standard otologic techniques and may require neurotologic dissections, such as a middle fossa craniotomy.

Surgical Techniques

The surgical exposure for cholesteatoma surgery usually requires either a postauricular or an endaural incision.

Facial Nerve

Care must be taken during dissection of the posterior-superior mesotympanum to avoid injury to the horizontal course of the facial nerve and the stapes or stapes footplate. The facial nerve in the horizontal segment is at greatest risk for surgical injury since dehiscences of the fallopian canal are common here. In general, identification of the horizontal course of the facial nerve in a severely diseased middle ear is easiest from the antrum and attic, just anterior and inferior to the horizontal semicircular canal.

Facial Recess and Epitympanum

Adequate exposure of the posterior-superior mesotympanum usually requires dissection of the facial recess. This can be accomplished with either the canal-wall-up or canal-wall-down tympanomastoidectomy in most cases. The canal-wall-down technique provides reliable access to this area. If the canal wall is kept up, the facial recess exposure needs to be extended into the attic by removing the incus buttress and the incus itself to provide adequate exposure.

The epitympanum is usually best exposed using the canal-wall-down technique, but an adequate exposure is usually obtainable using the canal-wall-up technique as long as there is adequate space between the top of the external auditory canal and the tegmen.

Canal Wall Considerations

The issue of whether a canal-wall-up or a canal-wall-down surgery should be performed is based on various factors. The first consideration relates to the surgeon's training level and experience often influences the choice. The second consideration is the anatomy of the patient's temporal bone. In some cases, adequate exposure can be obtained with either approach, in which case the surgeon may choose the approach based on other factors. In other cases, the canal-wall-down approach is necessary because anatomic features such as a low tegmen or an anterior sigmoid sinus do not allow adequate exposure with any other technique.

The third consideration in surgical approach is the issue of recurrent disease and recidivistic (residual) disease. There are diverse opinions about whether the canal-wall-up procedure leads to a higher incidence of recurrent or residual disease (or both). In general, the canal-wall-down procedure provides superior surgical exposure during chronic ear surgery, but in select cases, the canal-wall-up procedure with appropriate facial recess and epitympanum dissection provides an equivalent level of exposure. There are conflicting reports on whether the incidence of residual disease is higher in canal-wall-up cases, but the results are likely highly dependent on individual surgical techniques and the experience of the surgeon. However, there is compelling evidence that recurrence of cholesteatoma arising from the pars flaccida after the initial surgical treatment (new disease) is significantly higher in patients who have undergone the canal-wall-up procedure. Currently, this type of recurrence can be prevented only by performing canal-wall-down surgery, which essentially exteriorizes potential areas of recurrence such as the attic and the mastoid, or by obliterating these areas if the canal-wall-up or a canal-wall-reconstruction technique is used.

A cholesteatoma recurrence from the pars tensa is a less common problem, but this should be an important consideration, especially if the initial cholesteatoma was of this type. The preventive options include inserting a ventilation tube, placing cartilage grafts to stiffen the tympanic membrane, or obliterating the middle ear space by performing a radical mastoidectomy. The radical mastoidectomy is the most effective technique for preventing pars flaccida retractions, but this approach is not used routinely because patients' postoperative hearing results are uniformly poor.

Mastoid Cavity

The canal-wall-down tympanomastoid surgery, whether it is a radical or modified radical mastoidectomy, results in a mastoid cavity. There is a substantial amount of data pointing to a relatively high incidence of otorrhea and debris collection in mastoid cavities, even without the presence of residual or recurrent cholesteatoma. There are many suggested causes for this, but the most common causes, excluding cholesteatoma, are anatomic problems such as a high facial ridge and the presence of mucosal tissue within the mastoid cavity. Anatomic problems occur as a result of technical failure by the surgeon in creating an appropriately shaped mastoid cavity. The mastoid cavity must not have any residual bony ledges, which could cause the retention of squamous debris. A meatoplasty that allows for the adequate inspection and cleaning of the cavity in the office setting is also critical. The formation of mucosal tissue within the mastoid cavity typically occurs when a canal-wall-down procedure is performed in a mastoid that is well pneumatized, and therefore, a canal-wall-up surgery should be considered in these cases.

If the canal wall must be taken down, options include reconstructing the canal wall, obliterating the mastoid cavity with local flaps, such as the temporalis muscle or mastoid periosteum, and covering all exposed areas of mucosa with fascia grafts. The key concept in preventing mucosal overgrowth within the mastoid cavity is to suppress the growth of mucosa by removal or coverage.

Staging

Another controversial area in the surgical treatment of cholesteatoma is whether treatment should be staged. The reasons for planning a second surgical procedure include removal of any residual cholesteatoma and the reconstruction of the ossicular chain. Although complete cholesteatoma removal is the goal during the primary procedure, the surgeon, in some cases, may suspect that small pieces of cholesteatoma that are not readily visible could have been left in the surgical field. The most common areas of recurrence include the mesotympanum, in the area of the ossicular chain, and secondarily in the epitympanum. Residual disease in the mastoid is much less common.

Second-look surgery, usually performed 8–12 months after the initial surgery, is often performed after canal-wall-up surgery and less commonly performed after canal-wall-down surgery. The mastoid and epitympanum are highly unlikely to harbor residual cholesteatoma if these areas have been adequately exteriorized during the initial surgery.

A reason for delaying the ossicular chain reconstruction is to prevent adhesion formation around the reconstruction, which may adversely affect the hearing results. If there has been significant mucosal damage in the area of the oval window niche, the surgeon may elect to place a sheet of polymeric silicone (ie, Silastic) or other material to allow the mucosa to heal and form an adequately aerated middle ear space. Once this has been achieved, the surgeon may elect to perform a secondary surgery to reconstruct the ossicular chain. The choice of primary versus delayed ossicular reconstruction is based on the surgeon's experience and the surgical findings.

Perilymph Fistula

In general, cholesteatoma in the oval window niche is removed toward the end of the procedure so that management of any potential fistula into the vestibule can be instituted without the risk of compromising the repair during further dissection. The repair of an oval window or round window fistula usually consists of patching the defect with fascia or other soft tissue grafts.

There is a high rate of recurrent and residual cholesteatoma disease after primary surgical intervention. Over a time frame of 5 years or more, the combined rate of recurrent and residual disease has been reported to be as high as 40%. Many large series report a rate of 15–25% on follow-up of up to 10 years. The problem seems to be higher in the pediatric population.

The medical and surgical treatments that are available at this time cannot reverse all of the underlying physiologic elements in the ear that were responsible for the initial formation of the cholesteatoma. Chronic infection can usually be corrected, but if the underlying cause is significant eustachian tube dysfunction, this cannot be corrected primarily. The various surgical techniques discussed previously can help reduce the incidence of recurrent disease, but current techniques are not fully effective. Therefore, regular examinations over a course of 10 years or more after definitive treatment remain a critical part of the patient's care.

In most cases, patients are examined in the office setting once a year with the microscope. Symptoms suggestive of recurrent cholesteatoma are similar to those of an initial cholesteatoma, which were described previously. A recurrent cholesteatoma is relatively easy to detect based on the physical examination, at which point prompt treatment should be instituted to prevent both further damage to the temporal bone and other complications.