You are in: eMedicine Specialties > Radiology > HEAD AND NECK Temporal Bone, Acquired CholesteatomaArticle Last Updated: May 1, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 9
  Author: Salomon Waizel, MD, Associate Professor of Otolaryngology, Anahuac University; Consulting Surgeon, Department of Otolaryngology, Hospital De Especialidades, National Medical Center SXXI, IMSS, Associate Professor of Otolaryngology, Anahuac University; Consulting Surgeon, Department of Otolaryngology, Hospital De Especialidades, National Medical Center SXXI, IMSS Coauthor(s): Jose German Grandvallet, MD, Consulting Surgeon, Department of Otolaryngology, Medica Sur Medical Center, Mexico; Alejandro M Vargas, MD, Professor of Otolaryngology, National Autonomous University of Mexico; Department Head, Program Director, Department of Otolaryngology, Hospital De Especialidades, National Medical Center SXXI, IMSS; Anil Khosla, MD, Assistant Professor, Department of Radiology, Section of Neuroradiology Mallinckrodt Institute of Radiology, Washington University School of Medicine, Veterans Administration Medical Center-St Louis Editors: David S Levey, MD, PhD, Musculoskeletal Radiologist, Department of Magnetic Resonance Imaging, Radsource, LLC; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; C Douglas Phillips, MD, Professor, Departments of Radiology, Neurosurgery, and Otolaryngology, University of Virginia Health Sciences Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Lawrence M Davis, MD, Assistant Professor of Diagnostic Imaging (Clinical), Department of Diagnostic Imaging, Brown Medical School Author and Editor Disclosure Synonyms and related keywords: keratoma, congenital cholesteatoma, primary acquired cholesteatoma INTRODUCTIONSection 2 of 9
  BackgroundA 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. PathophysiologyCholesteatomas 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. FrequencyUnited StatesThe prevalence of acquired cholesteatoma in the United States is unknown. Congenital cholesteatoma is extremely rare. Mortality/MorbidityAs 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.
RaceRacial prevalence has not been proven. SexIn congenital cholesteatoma, the male-to-female ratio is 3:1. AgeLevenson et al have established an average age at presentation of 4.5 years for patients with congenital cholesteatoma.2 AnatomyPathologic 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:
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. Clinical DetailsThe 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 ExaminationOtoscopic 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 TechniquesBasically, 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. DIFFERENTIALSSection 3 of 9
Glomus Tumor (Head and Neck) Temporal Bone, Fractures Other Problems to Be ConsideredMiddle ear - Tympanic membrane perforation and benign tumor 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. RADIOGRAPHSection 4 of 9
FindingsConventional temporal-bone projections remain in use in many parts of the world where CT scanning and MRI are not available. Standard projections for the temporal bone include the Law, Schuller, Mayer, Owen, Chausse III, transorbital, Stenvers, submentovertical, and Towne views. Schuller, Stenvers, Towne, and submentovertical projections are the most useful in the diagnosis of acquired cholesteatoma of the temporal bone. The Schuller view is a lateral view of the mastoid, obtained with the sagittal plane of the skull parallel to the film and with 30º-cephalocaudal angulation on the radiographic beam. This view shows the degree and extent of mastoid pneumatization, the status of the trabecular pattern, and the position of the lateral sinus. The Stenvers view is obtained with the patient facing the film and the head slightly flexed and rotated 45º toward the side opposite the examination. The radiographic beam is angulated 14º caudad. The long axis of the petrous pyramid is parallel to the plane of the film, and the entire pyramid, including its apex, is well visualized. This view shows the entire pyramid, arcuate eminence, internal auditory canal, porus acusticus, horizontal and vertical semicircular canals, vestibule, cochlea, mastoid antrum, and mastoid tip. The submentovertical view (also termed axial or basal) is obtained from under the chin and has the advantage of showing both temporal bones on the same image. In this view, the external auditory canal, eustachian tube, middle ear (including the incus and the head of the malleus), mastoid air cells, styloid process, internal auditory canal, and petrous apex are visualized. This view also demonstrates the foramen ovale, foramen spinosum, and jugular foramen from the base of the skull. The Towne view is an anteroposterior projection with a 30º tilt. As in the submentovertical view, it allows comparison of both petrous pyramids and mastoids in the same image. The petrous apex, internal auditory canals, arcuate eminence, mastoid antrum, and mastoid process can be identified clearly. High-technology imaging modalities have become the radiologic methods of choice in the study of acquired temporal-bone cholesteatoma. Degree of ConfidenceDegree of confidence in radiography is low because of the complex anatomy of the temporal bone and the small radiologic changes induced by pathologic conditions. Interpretation of findings always depends on the experience of the physician. False Positives/NegativesThe false-negative rate with plain radiographs is high. CT SCANSection 5 of 9
FindingsCT-scanning technique Direct thin-section CT scanning in axial and coronal planes is a must for optimal evaluation of temporal-bone anatomy and pathology. Axial images are obtained parallel to the infraorbitomeatal line to reduce the radiation dose to the lens of the eye. Direct coronal images can be obtained in supine hanging-head position or prone with the neck extended. Axial images should include the top of the petrous apex to the inferior tip of the mastoid, and coronal images should be obtained from the anterior margin of the petrous apex to the posterior margin of the mastoid. Contiguous 1- to 1.5-mm-thick sections should be obtained by using conventional sequential acquisition. A spiral technique may be used if a pitch of 1:1 also is used. A small (12-cm) field of view can be applied with scans for each ear, reconstructed separately by using a bone algorithm. Intravenous contrast enhancement is usually not required. High-resolution CT scanning is ideal for the evaluation of middle-ear pathology. Contrast-enhanced CT scanning also is useful, if an intracranial complication is suspected and/or if a brain hernia (encephalocele) is present in the bed of the revision surgery. Recent advanced technology, such as multidetector-row scanning with submillimeter (0.5-mm) section thickness and high-speed rotation (0.5 second per rotation), has reinforced the benefits of CT scanning in assessing temporal-bone cholesteatomas. Applications of CT scanning CT scanning offers high-resolution images with a section thickness of approximately 1 mm, which allows for good visualization of the bony, ossicular, and inner-ear anatomies. On CT scans, good contrast is demonstrated for bone, soft tissue, and air. CT scanning is the preferred method for evaluating chronic middle-ear disease, including acquired cholesteatoma, because of its ability to demonstrate bony destruction. CT scanning is used to establish the surgical procedure needed in each patient. CT scanning helps to determine the extent of the cholesteatoma; the location and size of the sac; the status of the ossicular chain; the integrity of the facial canal, tegmen, and sinus plate; and the position of the dura, sigmoid sinus, and jugular bulb. CT-scan findings CT-scan findings in acquired temporal-bone cholesteatoma are characterized by a soft-tissue homogeneous mass with focal bone destruction. Cholesteatoma almost always presents as a complication of chronic otitis media; therefore, the middle-ear space appears cloudy as a result of granulation tissue, pus, and fluid. Liu and Bergeron have proposed the following CT-scan findings in cholesteatoma:4
Degree of ConfidenceCT scanning is considerably more sensitive than conventional radiography for detecting cholesteatomas. False Positives/NegativesGranulation tissue and a chronically infected middle-ear mucosa are almost impossible to differentiate from a cholesteatoma. MRISection 6 of 9
FindingsMRI technique Optimal MRI technique depends on the clinical situation and age of the patient. High-field-strength, contrast-enhanced imaging in the axial and coronal plane has been considered the criterion standard for evaluation of the internal auditory canal (IAC) and inner-ear structures. Nonenhanced and gadolinium-contrast-enhanced T1-weighted images are compared in order to differentiate bright lesions (fat and blood products) from enhancing lesions visualized after contrast infusion. Three-dimensional (3D) fast spin-echo T2-weighted images allow high-resolution imaging of the IAC and labyrinth. A variety of 3D gradient-echo techniques with thin sections also are available. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after they were given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes;joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape. Applications of MRI The role of MRI in the evaluation of middle-ear pathology is limited. The most important contributions of MRI to the study of acquired temporal-bone cholesteatoma are the following:
MRI defines the integrity of the dura, which is best appreciated with T2-weighted sequences, without the need for contrast material. However, in cases of dural infection, subtle contrast enhancement may be the only clue that dural involvement is present. MRI delineates intracranial extension of the cholesteatoma or protrusion of the intracranial contents into the middle ear, when defects of the tegmen tympani or sinus plate are visualized on the CT scan. MRI is also indicated when the facial nerve is involved. MRI findings Acquired cholesteatomas generally produce low signal intensity on T1-weighted images, with no change after contrast administration, and high signal intensity on T2-weighted images. MRI is also used to differentiate cholesteatomas from other temporal-bone lesions, such as cholesterol granulomas, granulation tissue, inflammatory mucosa, and scar tissue. Cholesterol granulomas produce high signal intensity on both sequences, with no contrast enhancement. Granulation tissue and inflammatory mucosa generally produce a hypointense or intermediate signal on T1-weighted images and a hyperintense signal on T2-weighted images with contrast enhancement. Because of its fibrous nature and, possibly, the microvascular thrombosis phenomenon, it is necessary to obtain delayed contrast-enhanced images with a delay of 30–45 minutes after contrast-material administration. Organized scar tissue produces a hypointense intermediate signal on T1- and T2-weighted images with no contrast enhancement. A study by Frederique Dubrulle shows the reliability of diffusion-weighted fast spin-echo MR imaging in the detection of recurrent cholesteatoma in patients who have undergone middle-ear surgery.5 Recurrent cholesteatoma was diagnosed if the lesion had low signal intensity on unenhanced T1-weighted images, showed no change in signal intensity on delayed contrast-enhanced T1-weighted images, and had high signal intensity on diffusion-weighted images obtained with a b factor of 800 sec/mm2. The negative predictive value was 100%, which means that patients who show no signs of recurrent cholesteatoma on diffusion-weighted fast spin-echo images may not need second-look surgery Degree of ConfidenceMRI is considerably more sensitive than conventional radiography, but it is less sensitive than high-resolution CT scanning, because of the lack of bone delineation on MRI. INTERVENTIONSection 7 of 9
The treatment of temporal-bone acquired cholesteatomas is surgical. Two principal techniques are used, depending on the decision regarding how to manage the posterior external auditory canal wall. The canal-wall-up procedure involves preserving the posterior canal wall with or without a posterior tympanotomy. The posterior tympanotomy is performed through a triangle bounded by the fossa incudis, facial nerve, and chorda tympani nerve. The canal-wall-down procedure involves taking down the posterior canal wall to the vertical facial nerve and marsupializing the mastoid into the external ear canal. Canal-wall-down procedures can be divided into those in which the middle-ear space is preserved (modified radical mastoidectomy) and those in which the middle-ear space is eliminated and the eustachian tube plugged (radical mastoidectomy). Medical/Legal Pitfalls
MULTIMEDIASection 8 of 9
REFERENCESSection 9 of 9
Temporal Bone, Acquired Cholesteatoma excerpt Article Last Updated: May 1, 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
