Diseases Affecting the External Auditory Canal
3 Diseases Affecting the External Auditory Canal
Keywords: external auditory canal, exostosis, osteomas, otitis externa, otomycosis, cholesteatoma, meningioma, facial nerve tumor, temporal bone fractures, squamous cell carcinoma
Pathologies affecting the external auditory canal (EAC) are a wide spectrum of diseases that include: bony neoformations of the EAC (exostosis and osteomas), inflammatory diseases (external otitis, otomycosis, and inflammatory stenosis of the EAC), cholesteatoma of the EAC, benign tumors of the ear and skull base extending to the EAC (carcinoid tumor, meningiomas, facial nerve tumors, etc.), temporal bone fractures, and carcinoma of the EAC. Otoscopy is fundamental for the recognition of each clinical condition. Analysis of patient clinical history and symptoms are also of utmost importance to decide the proper therapeutic management, which is different depending on the pathology. For example, in case of exostosis and osteomas occluding the EAC a canalplasty is indicated, as well as a surgical treatment is the mainstay for most of the benign and malign tumors involving the EAC. Further radiological examinations (CT and MRI scans) are indicated in the suspect of a tumor.
3.1 Exostosis and Osteomas
Exostosis are defined as new bony growths in the osseous portion of the external auditory canal (EAC). They are usually multiple, bilateral, and are commonly sessile. They vary in shape, being either round, ovoid, or oblong. The condition is caused by periostitis secondary to exposure to cold water. This explains the high incidence of exostoses among divers and cold-water bathers. Histologically, they are formed from parallel layers of newly formed bone. It is postulated that the periosteum stimulates an osteogenic reaction with each exposure to cold water, causing this stratification. When exostoses are small, they are asymptomatic. Large lesions, however, can occlude the EAC and lead to conductive hearing loss or retention of wax and debris with subsequent otitis externa. In such cases, and in cases in which a hearing aid is to be fitted, surgical removal of exostoses is indicated. In some cases, surgery is technically difficult and special care is taken to preserve the skin of the EAC. Other structures at risk are the tympanic membrane and ossicular chain medially, the temporomandibular joint anteriorly, and the third segment of the facial nerve posteroinferiorly.
Osteoma is a true benign neoplasm of the bone of the EAC, usually unilateral and pedunculated. Histologically, it can be differentiated from exostosis by the absence of the laminated growth pattern.
According to the extent of both diseases, we developed a classification for EAC stenosis, which is based mainly on the amount of tympanic membrane otoscopically visible ( ▶ Table 3.1; ▶ Fig. 3.1, ▶ Fig. 3.2, ▶ Fig. 3.3, ▶ Fig. 3.4, ▶ Fig. 3.5, ▶ Fig. 3.6, ▶ Fig. 3.7, ▶ Fig. 3.8, ▶ Fig. 3.9, ▶ Fig. 3.10, ▶ Fig. 3.11, ▶ Fig. 3.12, ▶ Fig. 3.13, ▶ Fig. 3.14, ▶ Fig. 3.15, ▶ Fig. 3.16, ▶ Fig. 3.17, ▶ Fig. 3.18, ▶ Fig. 3.19, ▶ Fig. 3.20).
All four quadrants of the pars tensa are perfectly visible.
100% of the pars tensa area is visible.
No narrowing of EAC
One or more quadrants is/are partially visible.
≥ 75% of the pars tensa area is visible.
10–25% narrowing of EAC
One of the quadrants is completely obscured.
50–75% of the pars tensa area is visible.
25–50% narrowing of EAC
Two of the quadrants are completely obscured.
25–50% of the pars tensa area is visible.
50–75% narrowing of EAC
Near total stenosis
Three of the quadrants are completely obscured.
10–25% of the pars tensa area is visible.
75–90% narrowing of EAC
None of the quadrants are visible.
0% of the pars tensa area is visible.
90–100% narrowing of EAC
*The degree of stenosis is calculated as a percentage of the maximum measurement available of the lesion against the maximum diameter of the EAC in axial and coronal cuts.
Abbreviation: EAC, external auditory canal.
Fig. 3.1 Right ear. Small exostosis originating from the superior wall of the external auditory canal. A hump on the anterior wall precludes visualization of the anterior–inferior quadrant of the tympanic membrane.
Fig. 3.2 Left ear. Small asymptomatic exostosis originating from the anterior wall of the external auditory canal.
Fig. 3.3 Right ear. Exostosis originating from the inferior and posteriors wall of the external auditory canal. According to our classification, this is a Grade I stenosis. This case should be simply followed up.
Fig. 3.4 Left ear. Bilateral Grade II stenosis of the external auditory canal for exostosis of the anterior wall. The tympanic membrane is viewable on its posterior quadrants. In this type of case, it is useful to photograph both ears for further follow-up within 1 to 2 years.
Fig. 3.5 Right ear. Same patient as in ▶ Fig. 3.4. Bilateral Grade II stenosis of the external auditory canal for exostosis of the anterior wall. The tympanic membrane is viewable on its posterior quadrants. In this type of case, it is useful to photograph both ears for further follow-up within 1 to 2 years.
Fig. 3.6 Right ear. Grade III stenosis for exostosis originating from the anterior and posterior walls of the external auditory canal. Less than 50% of the tympanic membrane is viewable. The patient complains of hearing loss and frequent episodes of otitis externa secondary to retention of water and debris inside the canal. A canalplasty under local anesthesia is indicated to restore the size of the external auditory canal.
Fig. 3.7 Right ear. Grade IV stenosis. Less than 20% of the tympanic membrane is visible. The occurrence of conductive hearing loss is high in this type of stenosis, so surgery is recommended.
Fig. 3.8 This figure and ▶ Fig. 3.9 correspond to computed tomography (CT) scans (axial and coronal cuts), which show exostosis from each wall of the external auditory canal of the patient in ▶ Fig. 3.6 and ▶ Fig. 3.7. These bony lesions show radiopacity. A preoperative CT scan is not fundamental but could be useful to check the amount of bone removal anteriorly (avoiding the opening of the temporomandibular joint: green arrow), posteriorly (avoiding the opening of the mastoid air cells or an injury of the third portion of the facial nerve: yellow arrows), and medially (avoiding an injury of the tympanic membrane and of the ossicles).
Fig. 3.9 Same patient as in ▶ Fig. 3.8. Computed tomography (CT) scans (axial and coronal cuts), which show exostosis from each wall of the external auditory canal. These bony lesions show radiopacity. A preoperative CT scan is not fundamental but could be useful to check the amount of bone removal anteriorly (avoiding the opening of the temporomandibular joint), posteriorly (avoiding the opening of the mastoid air cells or an injury of the third portion of the facial nerve), and medially (avoiding an injury of the tympanic membrane and of the ossicles: blue arrows).
Fig. 3.10 Right ear. Complete stenosis of the external auditory canal. The tympanic membrane is not visible. As a first evaluation of complete stenosis is important to ensure the bony consistency of these lesions through a gentle pressure with a hook. The patient usually does not refer pain after the maneuver. A CT scan is indicated in this case to check the condition of the middle ear.
Fig. 3.11 Right ear. Osseous neoformation of the external auditory canal. In this case, given the pedunculated narrow base, an osteoma is a more probable diagnosis. This was confirmed by pathological examination of the removed specimen. Ample bone removal is performed in such cases to avoid recurrence.
Fig. 3.12 Same patient. CT scan (axial cut) shows a pedunculated bony lesion of the anterosuperior wall of the external auditory canal.
Fig. 3.13 Left ear. Exostoses of the posterior and anterior walls of the external auditory canal and osteoma of anterosuperior wall. The lesions allow only a limited view of the tympanic membrane (Grade III stenosis). In this case, regular follow-up is necessary because further growth of the lesions could lead to accumulation of debris and cerumen, necessitating surgical intervention.
Fig. 3.14 Left ear. Osteomas of the superior wall of the external auditory canal. The pars flaccida of the tympanic membrane is not visible.
Fig. 3.15 Right ear. Same patient as in ▶ Fig. 3.14. Osteomas and exostoses allow visualization of the tympanic membrane only in the central part.
Fig. 3.16 Right ear. Osteoma occluding the external auditory canal with accumulation of wax and hearing loss. The pedicle of the lesion (anterior wall of the external auditory canal) is not well recognizable. Surgery is indicated in such case.
Fig. 3.17 Left ear. Exostoses with Grade III stenosis of the external auditory canal. A small perforation of the anteroinferior quadrant of the tympanic membrane is present. In this case, surgery includes a canalplasty combined with a myringoplasty.
Fig. 3.18 Left ear. Obstructing exostosis of the external auditory canal resulting in otitis externa due to accumulation of squamous debris inside the canal. Surgery is essential both to avoid the formation of cholesteatoma and to improve hearing.
Fig. 3.19 Left ear. Exostosis of the external auditory canal with a polyp that occludes the meatus. Local therapy is indicated. In case of no response, a CT scan is mandatory to exclude pathology affecting the middle ear and/or the mastoid.
Fig. 3.20 Left ear. Exostoses of the external auditory canal with severe stenosis (Grade III). This condition facilitates retention of ear wax with the onset of conductive hearing loss.
3.1.1 Surgery for Exostosis and Osteoma: Canalplasty
Even if usually asymptomatic, exostosis and osteoma may grow occluding the EAC. Surgery is indicated in case of obstructing stenosis (with or without hearing loss), or in case of frequent otitis externa where it is necessary to fit a hearing aid. In cases where symptoms are minimal, it is useful to photograph the ear for further follow-up. In surgery, preservation and proper replacement of the meatal skin is important to prevent postoperative scarring and stenosis. Osteoma can be removed with a curette. However, if osteoma recurs, wide drilling of the bone around its base is indicated.
In limited cases in which wide exposure is not required (i.e., small osteoma), a transcanal approach could be used. The meatal skin is incised through an ear speculum and the skin over the osteoma is elevated. The osteoma is then removed with either a curette or a burr.
Retroauricular incision is used in most of the cases since this approach is wider and safer than the transcanal approach. The initial steps of surgery including skin incision, harvesting the temporalis fascia, and soft tissue incision.
In case of severe exostosis, there is no consistent landmark in the EAC since the tympanic membrane is obscured ( ▶ Fig. 3.21). If there is any space medially, the skin is detached from the bone and to push medially toward the tympanic membrane. The skin may be protected with an aluminum sheet with/without a small piece of cottonoid beneath the sheet.
If the space medial to bony protrusions is insufficient to contain the detached skin, the skin covering the bony overhang is detached and folded toward the contralateral wall. Protecting the skin with an aluminum sheet, a part of the protrusion is drilled medially ( ▶ Fig. 3.22).
The meatal skin covering another protrusion is detached, and the flap is then folded toward the space created by the drilling. The aluminum sheeting is repositioned between the bony wall and the meatal skin flap, and the bony protrusion is partially drilled medially.
After partly drilling the second bony protrusion, the meatal skin is repositioned, and the first protrusion is drilled further. In this way, the canal is gradually drilled from lateral to medial.
The mastoid segment of the facial nerve runs in the vicinity of the posterior meatal wall, 2 to 3 mm posterior to the annulus. The reported incidence of iatrogenic injury to the facial nerve during surgery for exostosis is very high. To avoid injury, it is important to restrict the area of drilling around the meatal skin until the tympanic membrane is sufficiently visualized. Position of the tympanic membrane should be verified from time to time by replacing the meatal skin.
If protrusion still limits view of the tympanic membrane, the anterior canal wall may be drilled to help visualize the membrane, taking care not to damage the temporomandibular joint anteriorly ( ▶ Fig. 3.23). However, accidental exposure of the temporomandibular joint is better than damage of the facial nerve. Posterior canal should not be drilled too medially before verifying the area of drilling.
Using the meatal skin elevator (#2), quantity of bone to be drilled and distance from the annulus are estimated from time to time.
Removal of the final bony overhang may be conducted with a small curette ( ▶ Fig. 3.24). If the drill is used, care should be taken not to touch the short process of the malleus with a burr.
The exposed canal bone should be covered with the temporalis fascia. Longitudinal plastic cuts may be made in the meatal flap to assure intimate lining on the bone. Lateral meatal skin may also be cut longitudinally.
Surgery in cases of exostosis is indicated only in case with obstructing stenosis with or without hearing loss but with frequent otitis externa due to retention of debris. Surgery can be performed under local anesthesia, preferably using a postauricular incision. This approach allows excellent exposure of the whole meatus, thus minimizing the risk of injury to the tympanic membrane. In addition, it enables the surgeon to preserve the canal skin, thereby avoiding postoperative cicatricial stenosis. After dissecting the posterior limb, the flap is retained by the prongs of the self-retaining retractor. The skin of the anterior wall is incised medial to the tragus and is dissected in a lateral-to-medial direction. While drilling the exostosis, the skin of the canal is protected using an aluminum sheet (the cover of surgical sutures). Osteoma can be removed by using a curette. In case of recurrence, wide drilling of the bone around its base is also indicated.
Fig. 3.21 The tympanic membrane is obscured in severe stenosis (no landmarks).
Fig. 3.22 Skin flap folded on the opposite wall and protected with an aluminum sheet.
Fig. 3.23 Drilling of the anterior wall. TMJ, temporomandibular joint.
Fig. 3.24 Removal of the final bone overhang.
Fig. 3.25 Example of canalplasty. Right side. Exostoses of the anterior and posteroinferior walls of the external auditory canal and osteomas of the superior and posterior walls. A retroauricular approach has been performed and the meatal skin has been incised.
Fig. 3.26 The skin covering the exostoses has been detached and reflected anteriorly and medially. Osteomas are removed with a curette.
Fig. 3.27 The skin is pushed medially to the protrusions to make some room for drilling. To save time, most of the bone work is performed with cutting burrs.
Fig. 3.28 The canalplasty has reached the area of the tympanic membrane. Some bone overhang remains near the tympanic membrane. The final bony overhang can be removed with a small diamond burr and a curette. Great care should be taken not to touch the lateral process of the malleus during drilling the anterosuperior wall.
Fig. 3.29 The meatal skin is replaced over the bony wall. Note that the skin is well preserved, and the tympanic membrane remains intact.
Fig. 3.30 Postoperative otoscopy (6 months). The external auditory canal has been perfectly calibrated. All the tympanic membrane is visible.
3.2 External Auditory Canal Inflammatory Diseases
Eczema is a dermo-epidermal process of reactive nature resulting from local or general factors. Local factors include allergy, topical medical preparations, or cosmetics, whereas general factors include hepatic or gastrointestinal dysfunction. It manifests by itching, a burning sensation, vesication, and sometimes serous otorrhea. Treatment consists of discontinuing the suspected causative irritant, correction of the systemic disturbances, as well as lavage with boric acid with alcohol and steroid lotion (see ▶ Fig. 3.31, ▶ Fig. 3.32).
Fig. 3.31 Right ear. Chronic eczema of the external auditory canal. Squamous debris covering the skin of the external auditory canal can be observed. Successfully treated by the use of local steroid lotion.
Fig. 3.32 Chronic eczema of the external auditory canal skin. Exostoses and osteoma are also evident. The accumulation of skin debris and wax could lead to external otitis.
3.2.2 Otitis Externa
Otitis externa is an inflammation of the skin of the EAC. The inflammation can be secondary to dermatitis (eczema) only, with no microbial infection, or it can be caused by active bacterial or fungal infection. In either case, but more often with infection, the ear canal skin swells and may become painful or tender to touch. Acute otitis externa is predominantly a microbial infection (i.e., Pseudomonas aeruginosa). Wax in the ear can combine with the swelling of the canal skin and any associated pus to block the canal and dampen hearing to varying degrees, creating a temporary conductive hearing loss. In more severe or untreated cases, the infection can spread to the soft tissues of the face that surround the adjacent parotid gland and the jaw joint, making chewing painful. The two factors that are required for external otitis to develop are: the presence of germs that can infect the skin and impairments in the integrity of the skin of the ear canal that allow infection to occur. However, if there are chronic skin conditions that affect the ear canal skin, such as atopic dermatitis, seborrheic dermatitis, psoriasis, or abnormalities of keratin production, or if there has been a break in the skin from trauma, even the normal bacteria found in the ear canal may cause infection and full-blown symptoms of external otitis. At the otoscopic examination, the canal appears red and swollen. Touching or moving the outer ear increases the pain, and this maneuver on physical exam is important in establishing the clinical diagnosis. Therapy consist of cleaning the ear with 2% alcohol boric, instillation of local antibiotic, oral antibiotic, and analgesic in advanced cases. Necrotizing external otitis (malignant otitis externa) is an uncommon form of external otitis that occurs mainly in elderly diabetics, being somewhat more likely and more severe when the diabetes is poorly controlled. Even less commonly, it can develop due to a severely compromised immune system. Beginning as infection of the external ear canal, there is extension of infection into the bony ear canal and the soft tissues deep to the bony canal with further extension to the skull base. Necrotizing external otitis requires oral or intravenous antibiotics for cure (fluoroquinolones plus cephalosporins), even for more than 2 weeks. Diabetes control is also an essential part of the treatment (see ▶ Fig. 3.33, ▶ Fig. 3.34, ▶ Fig. 3.35, ▶ Fig. 3.36, ▶ Fig. 3.37).
Fig. 3.33 Acute otitis externa. The external auditory canal appears swollen with skin debris and some otorrhea. The tympanic membrane is not visible. In case of no response after appropriate and prolonged therapy, it’s important to exclude malignant disease that could get into differential diagnosis (i.e., carcinoma of the external auditory canal).
Fig. 3.34 A polyp-like mass is present in the external auditory canal. The patient, who had already undergone two tympanoplasties, complained of pain in the ear. He has suffered from diabetes for 15 years. A biopsy performed under local anesthesia excluded neoplastic disease. A scintigraphic examination confirmed the diagnosis of malignant external otitis. The patient was treated with a long course of antibiotic therapy, with final resolution of the pathology.
Fig. 3.35 Right ear. Malignant otitis externa in a 60-year-old patient affected by type I diabetes. The otoscopy is similar to that in ▶ Fig. 3.33. The patient had no remission with standard antibiotic therapies and developed skull base osteomyelitis (confirmed by CT scan, MRI, and scintigraphy). She further developed facial nerve and lower cranial nerves paralysis, which recovered after hospitalization and intravenous antibiotic therapy. The patient is still under antibiotic therapy (duration 4 months) with slight improvement of the clinical condition.
Fig. 3.36 Gallium67 scintigraphy shows accumulation of the radionuclide at the level of the temporal bone, the temporomandibular joint, and the clivus. This technique is useful in diagnosis as well as for monitoring the response to treatment and detecting recurrence.
Fig. 3.37 CT scan. Axial view. Bone erosion is evident at the level of the anterior wall of the external auditory canal (white arrow) and the petrous apex (yellow arrow). The pathology completely involves the middle ear and the mastoid.
Foruncolosis is a pustular folliculitis by staphylococcal infection of a hair follicle. Infection occurs as a result of microabrasion or of decreased immunity, as in diabetics. It is characterized by severe pain. A tender swelling is seen in the cartilaginous part of the EAC, which may have a central necrotic part (see ▶ Fig. 3.38).
Fig. 3.38 A furuncle almost totally occluding the meatus. Pain is caused by distention of the richly innervated skin. A central necrotic part is seen.
Otomycosis is more common in tropical and subtropical countries. In the majority of cases, the isolated fungi are of the Aspergillus (niger, fumigatus, flavescens, albus) or the Candida species. Otomycosis is more common in immunocompromised patients and in diabetics. Local factors that favor fungal infections include chronic otorrhea and the presence of epithelial debris. Clinically, the patient complains of otorrhea, itching, and hearing loss. Therapy consists of cleaning the ear to remove all debris and the instillation of local antimycotic preparations as well as lavage with 2% alcohol boric acid drops (see ▶ Fig. 3.39, ▶ Fig. 3.40, ▶ Fig. 3.41, ▶ Fig. 3.42, ▶ Fig. 3.43).
Fig. 3.39 Right ear. Radical mastoid cavity showing cholesteatoma with superimposed fungal infection.
Fig. 3.40 An ear with chronic suppurative otitis media with cholesteatoma showing a superimposed fungal infection. The blackish fungal masses are early recognized. They should be removed before local antifungal solution is instilled.
Fig. 3.41 Another example of otomycosis in a radical mastoid cavity.
Fig. 3.42 Right ear. Otomycosis (Candida infection). The patient suffered from chronic otitis with occupational exposure to humid environments. The external auditory canal is filled with whitish lamellar material. Usually, it is not necessary to perform a culture of ear secretions and the diagnosis is clinical. The lack of response to a topical antibiotic therapy is a further confirmation of the fungal nature of the infection.
Fig. 3.43 Same ear after 10 days therapy with ear lavages and antimycotic drops. The external auditory canal is almost free from fungal secretions. A simple perforation of the inferior quadrants of the tympanic membrane is visible.
3.2.5 Myringitis and Meatal Stenosis
Myringitis is an inflammatory process that affects the tympanic membrane. Three forms are recognized: acute myringitis, bullous myringitis, and myringitis granulomatosa. Acute myringitis is usually seen in association with infection of the external ear (otitis externa) or middle ear (otitis media). It is characterized by hyperemia and the presence of purulent secretions. Therapy consist of administration of general and/or local antibiotics and local steroids. Bullous myringitis is commonly associated with viral upper respiratory tract infection. It is characterized by the presence of bullae filled with serosanguineous fluid. The bullae are located between the outer and the middle layers of the tympanic membrane. The patient complains of otalgia and hearing loss. Therapy consist of antibiotics and steroids. In granulomatous myringitis, the outer epidermic layer of the tympanic membrane as well as the adjacent skin of the EAC are replaced by granulation tissue. It is generally seen in patients suffering from frequent episodes of otitis externa. In some cases, it may ultimately lead to stenosis of the most medial part of the EAC. It can usually be cured, however, by removing the granulation in the outpatient clinic using the microscope. This is followed by the administration of local steroid drops for nearly 1 month. In refractory cases, however, surgery in the form of canalplasty with free skin graft is necessary (see ▶ Fig. 3.44, ▶ Fig. 3.45, ▶ Fig. 3.46, ▶ Fig. 3.47, ▶ Fig. 3.48, ▶ Fig. 3.49, ▶ Fig. 3.50, ▶ Fig. 3.51, ▶ Fig. 3.52, ▶ Fig. 3.53, ▶ Fig. 3.54, ▶ Fig. 3.55, ▶ Fig. 3.56, ▶ Fig. 3.57, ▶ Fig. 3.58, ▶ Fig. 3.59).
Fig. 3.44 Left ear. The tympanic membrane is characterized by thickening and hyperemia. In this case, the skin of the external auditory canal is also hyperemic. The tympanic membrane seems lateralized.
Fig. 3.45 Acute myringitis of a left tympanic membrane. The area of the malleus handle is hyperemic and the tympanic membrane seems lateralized. A small tympanic perforation is visible in the anterior–inferior quadrant.
Fig. 3.46 Acute myringitis. The tympanic membrane over the malleus handle is hyperemic. A large tympanosclerosis plaque is visible on the posterior quadrants.
Fig. 3.47 Left tympanic membrane with a large bulla anterior to the malleus and a smaller one posterior to it.
Fig. 3.48 Right bullous myringitis. The patient complained of a bad flu few days before the examination. Bleeding from the ear is quite common, due to the rupture of the bullae.
Fig. 3.49 Granulomatous myringitis. The granulomatous tissue has replaced the external skin layer of the tympanic membrane and part of the anterior wall of the external canal. This case was treated by removal of the granulation tissue under local anesthesia in the outpatient clinic. Local steroid drops were then administered for 1 month.
Fig. 3.50 Postinflammatory stenosis of the right external auditory canal of a 68-year-old woman. The patient complained of bilateral continuous otorrhea and hearing loss of 3 years’ duration. The otorrhea in the left ear stopped 2 months before presentation. The granulations over the tympanic membrane were removed in the outpatient clinic. A cellophane sheet was inserted into the external auditory canal to avoid the reformation of stenosis. Local steroid drops were administered for 1 month. On follow-up, stenosis was already resolved and the granulation tissue in the external auditory canal was completely replaced by healthy skin.