John K. Niparko
Sara Love-Schlessman
Howard W. Francis
In the United States, an estimated one in nine people develops a permanent hearing impairment that diminishes the ability to carry out everyday communication. Hearing loss is especially common in the elderly, who account for 40% of the hearing impaired. In fact, the only chronic disorders that are more prevalent are hypertension and arthritis. Many causes of hearing impairment are preventable. Early detection and intervention can often ameliorate an acquired hearing impairment.
When evaluating a patient with hearing loss, the practitioner should determine the mechanism of loss (conductive or sensorineural), the likely cause, and the need for referral to an otolaryngologist for further evaluation. This chapter includes a brief review of the anatomy and physiology of the auditory system that will help in understanding auditory pathology, and details strategies of diagnosis and early treatment.
Ear Structure and Function
The external ear (Fig. 110.1) is composed of the auricle, the auditory meatus, and the external ear canal. The outer portion of the canal is cartilaginous and is covered by thick skin that contains hair follicles and the cerumen-secreting glands; cerumen protects the epithelium and captures foreign particles entering the canal. The inner portion of the canal is bony and is covered by squamous epithelium without hair follicles or cerumen glands.
The middle ear (Fig. 110.1) consists of the tympanic membrane, the air space behind it, and the three linked ossicles: the malleus, incus, and stapes. The malleus is attached to the tympanic membrane and is linked to the stapes by the incus. The stapes makes contact with the inner ear via the stapes footplate at the oval window. The middle ear is lined with a mucus-secreting epithelium similar to that which lines the nose. The middle ear communicates with the nasopharynx via the eustachian tube and posteriorly with the mastoid air cells. Intermittent opening of the eustachian tube ensures equal pressure on either side of the tympanic membrane, which facilitates the transmission of sound from the tympanic membrane to the oval window.
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FIGURE 110.1. Normal structures of the ear. |
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The inner ear (Fig. 110.1) lies within the temporal bone of the lateral skull base and is encased in the compact otic capsule and is fluid filled. It consists of sensory organs for hearing (cochlea) and balance (vestibular labyrinth). Nerves from the cochlea and vestibular labyrinth unite to form the eighth cranial nerve.
Cranial nerve VII (facial) traverses the temporal bone in close association with the middle and inner ear structures. For this reason, facial muscle paresis and paresthesias of the anterior two-thirds of the tongue and soft palate may manifest from pathologic processes of the middle and inner ear.
Sound is funneled through the auricle into the external ear canal, vibrating the tympanic membrane; the vibration is transferred across the ossicular chain. The large surface area of the vibrating tympanic membrane, and the lever action of the ossicles improve sound transmission to the inner ear, where vibrations of the stapes footplate create a fluid wave in the cochlea. This wave stimulates the hair cells that translate vibratory energy into action potentials that trigger auditory neurons.
Determining Severity and Mechanism of Hearing Loss
Regardless of the specific cause of hearing loss, the approximate severity of the impairment and the probable cause can often be determined in the office. This determination can be made from a combination of the history, the patient's ability to hear the spoken voice, and testing with a tuning fork.
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TABLE 110.1 A Practical Method for Approximating the Severity of Hearing Loss in the Office |
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Suggested Questions for History
To help establish a differential diagnosis for the possible causes of hearing loss, the following information should be acquired:
Evaluating the Severity and Range of Hearing Impairment
A practical method for evaluating the severity of hearing impairment includes a historical estimate of speech recognition impairment in noisy settings and an assessment of response to voice testing in the office; these two findings can be equated with various levels of abnormality in the audiogram (Table 110.1). Slight impairment indicates difficulty in hearing distant speech in noise (e.g., group meetings, social gatherings, or the theater). Moderate impairment includes some difficulty with short-distance speech and conversation. Severe impairmentindicates no understanding of the conversational voice but understanding of the amplified voice. Amplification may be achieved by raising the voice or electronically by use of a hearing aid (see Hearing Aids). Profound (or total) impairment indicates inability to hear and understand the spoken voice despite maximal
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amplification. This also may be summarized by recalling that a soft whisper is about 25 decibels (dB), a moderate whisper is about 40 dB, and conversational speech is about 60 dB. In the office, ambient sound can markedly affect the ability of a patient with hearing impairment to respond to this cursory assessment of audition. Therefore as quiet an environment as possible is advised.
In the patient with significant hearing impairment, the frequency range can be approximated in the office by testing recognition of words containing the sound “ah” (low frequency, vowel sound), such as apple, hot dog, and airplane, and the sounds “s” (high frequency, consonant), such as ice cream, stairway, baseball, and sunset, when these words are spoken in a medium voice about 2 feet behind the test ear, with the opposite ear covered.
Physical Findings
Otoscopy
Assessment of the External Canal and Tympanic Membrane
Complete inspection of the external ear canal and drum requires pulling the pinna in a posterosuperior direction to align the membranous and bony portions of the canal. The entire drum should be inspected (Fig. 110.2), particularly the posterosuperior aspect, where chronic inflammatory changes often occur. Cerumen accumulation in this region of the drum is unusual and may suggest an underlying problem (Fig. 110.3).
Membrane Mobility
During the otoscopic examination, it is important to assess tympanic membrane mobility with air insufflation. To do this, the examiner must seal the otoscope speculum tip with the ear canal. The absence of mobility suggests a pathologic condition such as negative pressure consequent to eustachian tube dysfunction, middle ear fluid, or a mass.
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FIGURE 110.2. Right tympanic membrane, showing important landmarks. |
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FIGURE 110.3. Cross-sectional drawing of middle ear depicted in Figure 110.1. Arrow indicates the region of the tympanic membrane that may develop a retraction. Retraction pockets may accumulate desquamated debris and extend into regions of the epitympanum depicted by asterisks. |
Preliminary Hearing Testing
Tuning Fork Tests
The mechanism of hearing loss can be classified as conductive or sensorineural through use of a 512-Hz tuning fork. Conductive losses result from external or middle ear disease, whereas sensorineural losses are caused by an inner ear or auditory neuronal problem.
Weber Test
For Weber's test, the tuning fork is held against a spot in the midline of the forehead and the patient is asked in which ear it sounds louder (Table 110.2). A unilateral conductive hearing loss with normal bilateral inner ear function produces a louder sound in the affected ear. A unilateral sensorineural hearing loss produces a louder sound in the normal ear.
Rinne Test
In the Rinne test, the vibrating tuning fork stem is placed against the mastoid bone and held in place until it becomes no longer audible, then it is held about an inch away from the external meatus (Table 110.2). The Rinne test can differentiate conductive from sensorineural
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hearing losses. Air conduction is perceived after the bone conduction extinguishes with normal hearing and with sensorineural hearing loss, whereas the reverse is true for conductive losses. Alternatively, one can compare the perceived loudness of bone versus air conduction.
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TABLE 110.2 Classification of Probable Mechanism of Hearing Loss Using Tuning Fork Tests |
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Speech Recognition Testing
In patients with sensorineural hearing loss, impaired understanding of speech may differentiate cochlear and neural (retrocochlear) deficits. In the latter condition, patients generally have a greater reduction of speech discrimination than do those who have cochlear disorders. Recruitment, a sense of ear discomfort with sudden increments in the loudness of a sound, is characteristic of cochlear dysfunction.
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FIGURE 110.4. Examples of audiograms. A: Audiogram in a person with normal hearing. B: Bilateral conductive hearing loss (moderate). C: Bilateral sensorineural hearing loss (severe). (From Price LL, Snider RM. The geriatric patient: ear, nose, and throat problems. In: Reichel W, ed. Clinical aspects of aging. Baltimore: Williams & Wilkins, 1978;404. ) |
Audiometry
Whereas the office examination can only approximate the loss, audiometric evaluation establishes the precise level of hearing loss. Pure tone air conduction and bone conduction measurements are made for sounds of varying intensity (decibels) and frequency. Results are plotted on a graph called an audiogram in which the vertical axis shows the sounds heard in decibels and the horizontal axis shows the frequency of the stimulus in Hertz. Figure 110.4 reproduces examples of audiograms showing normal hearing, conductive hearing loss, and sensorineural hearing loss. Speech audiometry measures the subject's ability to hear and understand the spoken word.
Audiometry is performed by audiologists, some of whom have their offices in association with an otolaryngologist. Many, however, are independent. Patients can be referred directly to an audiologist from a primary care physician. The location of an accredited audiologist can be obtained by telephoning the action line of the American Speech-Language Association (ASHA) at 800-638-8255 or http://www.ASHA.org.
An audiogram is easily accomplished when proper testing facilities are available. The patient is comfortably seated in a soundproof room and is asked to record the sounds heard. A series of pure tones are presented to the patient. The procedure takes only about 20 to 30 minutes.
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Small hand-held audioscopes, costing about $500, are available for use in the office by general physicians. These are useful as a rough screen of hearing impairment. Usually four pure tones are emitted in sequence. Because of masking effects, background noise can adversely affect a patient's ability to respond to test signals and the examining room must be quiet.
The lowest audible intensity for normal ears is approximately 10 to 20 dB (Fig. 110.4). Conversational speech is typically delivered at 45 to 55 dB. The ASHA has categorized hearing loss as mild (26 to 40 dB), moderate (41 to 55 dB), moderately severe (56 to 70 dB), severe (71 to 90 dB), and profound (greater than 91 dB).
An assisted listening device can be valuable in conversing in the office with a patient who is hearing impaired. This device is simply a system of a microphone, amplifier, and earphones. It also reduces some of the background noise in the room and amplifies the examiner's spoken word. Such devices can be obtained in electronics stores or by ordering directly from a manufacturer (e.g., Pocketalker, Williams Sound, telephone 800-328-6190; or Chorus, Audiological Engineering Corp., 800-283-4601).
After this initial evaluation, the presence or absence of hearing loss should be established. If there is hearing loss, it should be determined whether it is primarily unilateral or bilateral and whether it is primarily sensorineural or conductive. Further assessment and care for patients with moderate or severe hearing loss usually requires the assistance of an otolaryngologist. An asymmetric hearing loss should prompt a referral for more sophisticated testing (see discussion of specific conditions below).
Causes of Hearing Loss: Overview
Table 110.3 lists the major causes of hearing loss in adults. For each condition, the table indicates mechanism, onset (rapid or gradual), and whether the condition is typically unilateral or bilateral. The guidelines that follow will enable the general physician to reach a working diagnosis in most instances and to choose between primary treatment and referral for care by a specialist.
Conditions of the External Ear
Cerumen Impaction
The patient usually complains of intermittent fullness and hearing impairment on the affected side and may give a history of episodes. These symptoms may increase after showering or swimming, as moisture occludes the ear canal, or with cotton-tipped swab use. Diagnosis is made by otoscopy.
Several precautions should be kept in mind in considering cerumen removal. An only hearing ear, a postsurgical ear, and an ear that is prone to infection (as with any form of immunocompromise) should not be irrigated. If the drum is not visible, it is advisable to defer irrigation to reduce any worsening of the cerumen impaction. If the cerumen appears to be soft, it may be removed by irrigation with use of a rubber-bulb or other syringe and warm tap water, directing the water upward and backward against the wall of the canal. If painful, irrigation should be discontinued and the patient referred to an otolaryngologist. If the cerumen is hard and difficult to remove, a few drops of hydrogen peroxide (or carbamide peroxide, Debrox) should be instilled twice daily for 1 week before irrigation. An alternative approach is for the patient to use mineral oil or baby oil drops in the ear on a regular basis as both effectively liquefy cerumen.
Alternatively, a ceruminolytic agent (Cerumenex) may be used. Generally, ceruminolytic agents should be used only in the office because casual use by the patient at home increases the risk of allergic dermatitis. With the patient's head tilted laterally at a 45-degree angle, the ear is filled with ceruminolytic drops. A cotton plug is inserted for 15 to 20 minutes; the ear is then irrigated with lukewarm water and a soft rubber or other syringe. After irrigation, the tympanic membrane usually shows some injection around the handle of the malleus. Hearing impairment should be relieved after removal of cerumen. The occasional patient with an impaction may not respond to the usual measures described above and should be referred to an otolaryngologist.
Complications from ear irrigation include pain, tympanic membrane perforation, dizziness, bleeding, tinnitus, retention of water behind incompletely removed wax, and infection. Complications requiring specialist referral occur in general practice at the rate of about 1 in 1,000 ears syringed (1). Tympanic membrane rupture, ossicular rupture, round and oval window fistulae, and subluxation of the stapedial footplate have been reported after oral jet irrigation use (2).
An impaction often follows vigorous efforts by the patient to remove wax with a cotton-tipped swab. The patient should be reminded that ear wax is secreted to protect the lining of the canal and that the swab should be used only to remove cerumen in the outer portion of the canal, for cosmetic purposes.
Recurrent impactions are often caused by eczema of the skin of the external ear canal as the desquamated debris impedes cerumen movement. Often topical therapy of the skin condition (see Otitis Externa) is critical to avoiding repeated cerumen accumulation and infection.
Foreign Body
Foreign bodies in the ear canal are most often the result of accidental insertion or entrance of an insect, which is followed by fullness and hearing impairment. Foreign bodies
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can be removed by the use of alligator forceps or a wax spoon. Removal by irrigation should be avoided if the foreign body is a vegetable, as water causes further swelling. Insects should first be killed by instillation of mineral oil. Hearing impairment resolves promptly after removal of a foreign body. Great care must be taken to avoid damage to the eardrum, especially in children and patients in whom the foreign body is deeply imbedded. In difficult extractions, an otolaryngologist may suggest anesthesia, either local injection or general.
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TABLE 110.3 Causes of Hearing Loss in Adults |
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Otitis Externa (Swimmer Ear)
Otitis externa is most common in the summer, when heat and moisture promote swelling and maceration of the stratum corneum of the skin. In the external canal, this process may at first cause pruritus. The patient may give a history of having scratched the ear for a few days before the onset of drainage and pain. The pain is aggravated by movement of the external ear and jaw motion. Hearing impairment occurs in patients with swelling or debris that occludes the canal. The characteristics of the skin of the canal and of the exudate may provide adequate clues to the cause, and cultures are needed only for patients who do not respond promptly to topical treatment. Copious or greenish exudate suggests Pseudomonas aeruginosa, the bacteria most often seen in otitis externa. Yellow crusting in the midst of a purulent exudate suggests Staphylococcus aureus. Canal skin that is scaling, cracked, and weeping indicates secondary eczema. Fluffy material resembling bread
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mold, varying in color from white to black, suggests a fungal agent (Aspergillus or Candida).
There are three general principles of treatment for all types of otitis externa: removal of all infected debris (with a suction cannula if available), acidification of the canal to inhibit bacterial and fungal growth, and instillation of an appropriate topical antimicrobial (see next paragraph). Lavage with hydrogen peroxide, commonly done in the past, is not recommended because it may be irritating to the inflamed and sensitive tissues and it is not adequately cidal to microbes.
For bacterial infections the patient should instill an antimicrobial-corticosteroid preparation (e.g., Cortisporin Otic Suspension, containing polymyxin B–neomycin–hydrocortisone, three or four drops three to four times daily for 5 to 7 days). Alternative topical antimicrobial agents include ofloxacin otic solution (Daiichi) and ciprofloxacin hydrochloride with hydrocortisone (Bayer), which are well tolerated. The use of Cortisporin otic solution, however may be painful to the inflamed ear and should be avoided in preference for the suspension. Gentle daily irrigation of the canal by the patient with a solution of acetic acid (50:50 white vinegar in sterile water) either alone or with steroids has the dual benefit of debriding infected material and acidifying the canal.
We emphasize that aminoglycoside preparations such as Cortisporin Otic remain the mainstay of topical antibiotic therapy for external otitis and selected cases of otitis media. This approach appears to avert intractable infection associated with microbial resistance. If potentially ototoxic antibiotics such as one containing an aminoglycoside are prescribed, the patient should be warned of the risk as well as instructed to contact their physician if dizziness, vertigo, additional hearing loss tinnitus occur. To address ototoxicity concerns, in 2004 a panel of otolaryngologists developed a consensus position for the treatment of otitic disease with topical antibiotics (3). The recommendations held that in the event of a known tympanic membrane perforation preparations free of potential ototoxicity should be used. Quinolone-containing otic topicals offer such a preparation. However, bacterial resistance to quinolones is increasingly recognized. Quinolone-resistantStreptococcus pneumoniae have achieved the status of “super bugs” in that there are no antibiotics available for therapy against these pathogens (4). Clearance of the bacteria under microscopic assistance with thorough cleaning of the ear canal likely reduces the risk of the emergence of resistant organisms with any topical therapy. Notwithstanding the above recommendations, otolaryngologists commonly use topical aminoglycoside preparations in practice (5,6). Clinical ototoxicity attributable to topical therapies for otitis externa has not been evident in the literature or practice, and is even rare when used in patients with otitis media with perforation (5, 6, 7).
For fungal infections, the canal should be thoroughly cleaned out and lightly dusted with sulfanilamide powder by the clinician. A dispenser containing sulfanilamide powder for this use can be obtained from any pharmacy. The fungal infection usually resolves after a single dusting with this powder. Clotrimazole (Lotrimin) 1% solution, three drops twice a day for 14 days, is an effective alternative. Daily irrigations with an acetic acid preparation also provide benefit. Topical steroid creams may be needed to address excessive desquamation.
For eczema without superimposed infection, a topical steroid cream is applied daily for 14 days (e.g., triamcinolone 0.1%). If satisfactory control has been achieved with the steroid, then chronic symptoms, which are very common, may be controlled by weekly and, eventually, monthly applications.
In some patients, the canal may be so swollen that topical medication does not enter the canal adequately. In this case, a cylindrical cotton wick (or a commercially available sponge wick, such as Oto-wick) should be inserted by gentle twisting into the canal until only the end is visible. The patient may then apply several drops of the medication to the wick three to four times daily, and the wick will carry it into the canal. The wick can usually be removed after 48 to 72 hours, and treatment can be continued as stated above.
Most episodes of otitis externa resolve completely after 5 to 7 days, and it is important to terminate topical treatment at this time. Topical medicines alter the canal environment and persistent treatment often leads to atopic or chemical dermatitis or fungal colonization. As a precaution against overtreatment, the prescription for eardrops should be nonrefillable, and only a small amount (10 mL) should be dispensed.
During treatment of otitis externa, moisture must be kept from entering the ear canal. During bathing, the ear should be plugged with cotton impregnated with petroleum jelly. To prevent recurrence, the patient should be warned against the future use of cotton-tipped swabs or other objects in the ear. Hearing impairment caused by otitis externa should resolve promptly when swelling recedes.
In two situations, the patient with otitis externa requires prompt referral to an otolaryngologist: patients whose findings suggest mastoiditis(slow response of the otitis externa to treatment and tenderness over the mastoid process); and patients whose findings suggest malignant otitis externa, usually diabetic or immunologically impaired patients. Malignant otitis externa is an osteitis of the bone underlying the external auditory canal, caused by Pseudomonas. The distinguishing features are fever, excruciating pain, and the presence of friable, reddish granulation tissue that fills a breach in the canal epithelium. Because of the propensity for rapid spread to contiguous structures, this condition is an emergency, requiring hospital admission for débridement and intravenous antibiotics.
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New Growth
Malignancies of auricular and periauricular skin are both common and notoriously difficult to control (8,9), and any suspicion of a new growth should prompt urgent referral to an otolaryngologist. Cutaneous malignancies that commonly occur in these sites are basal cell carcinomas and squamous cell carcinomas, which often exhibit aggressive clinical characteristics. Moreover, multiple tissue planes and the topography of this region can confound cure (Fig. 110.5). If diagnosed late, cutaneous malignancies of the auricle, pre-auricular region and external auditory canal often extend along embryologic planes to involve deep structures such as the parotid gland, and may erode into the mastoid cortex en route to the skull base. The morbidity and mortality associated with such extensions underscore the importance of early complete initial removal of malignancies in this region. Malignancies of the external auditory canal commonly present with a history of chronic otitis externa the prolonged treatment of which results in delayed diagnosis and treatment. Early referral of patients with suspicious ear lesions and refractory otitis externa is recommended.
Conditions of the Middle Ear
Conductive hearing loss is produced by conditions of the middle ear, tympanic membrane, and external ear canal. Most commonly, however, conductive hearing loss results from interference with the sound transformer mechanism of the tympanic membrane and middle ear ossicles. In addition to the history, the middle ear assessment includes otoscopic inspection for signs of acute inflammation (erythema, discharge, or bulging of the tympanic membrane), changes in the tympanic membrane not caused by acute inflammation (retraction, scarring, distortion of normal structures, perforation), cholesteatoma (squamous debris accumulation within the middle ear), and evidence of reduced middle ear aeration as indicated by diminished movement of the drum on pneumatic insufflation.
Serous Otitis Media
The patient usually complains of fullness and decreased hearing in one or both ears with minimal or no pain. There is often a history of recent viral upper respiratory infection, exacerbation of allergic or vasomotor rhinitis, or prior acute otitis media. Rarely, serous otitis media may be caused by nasopharyngeal carcinoma, and this possibility must be ruled out in adults with a new onset of serous otitis that does not resolve after appropriate management (see this section). There is otoscopic evidence of eustachian tube closure and retraction of the tympanic membrane, failure of the membrane to move on pneumatic otoscopy (a crude test of eustachian tube patency, but not always abnormal in serous otitis), or a visible air–fluid level behind the membrane. Usually the tuning fork test reveals a conductive hearing loss (see Preliminary Hearing Testing and Table 110.2).
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FIGURE 110.5. Cutaneous malignancies of the ear. A: Axial cross-sectional drawing of ear and temporal bone indicating potential paths of spread of cutaneous malignancies originating on the auricle, the pre-auricular region and external auditory canal. M: mastoid; P: parotid gland; T: temporomandibular joint. B: Axial computerized tommography of head, indicating soft-tissue obliteration of the right ear canal (*) and erosion of its bony walls (arrowheads). |
Medical management consists first of using systemic antibiotics as chronic middle ear effusions are culture positive in up to 50% of cases. Recommended regimens include a 10-day course of amoxicillin alone or combined with clavulanate, cefuroxime axetil, cefaclor, or trimethoprim–sulfamethoxazole (10,11). Topical decongestants in the form of nasal sprays or drops are often used to relieve
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eustachian tube obstruction. Nasal sprays containing sympathomimetics may be obtained over the counter (e.g., Neo-Synephrine 0.25% or 0.50% spray or drops). After 3 to 4 days of topical treatment, rebound nasal mucosal hyperemia may occur. Therefore the patient should be instructed explicitly to discontinue spray (or drops) after 3 days. Systemic decongestants (e.g., pseudoephedrine) are probably not helpful (12). If serous otitis media coincides with symptoms of allergic rhinitis, Eustachian tube function and middle ear aeration may be helped by the use of a nasal steroid spray for a few weeks or the duration of the seasonal allergy alone or in combination with an antihistamine (seeChapter 30).
All patients should be reevaluated after 4 to 6 weeks. If conductive hearing loss persists beyond 6 weeks, the patient should be referred to an otolaryngologist, who will confirm and quantify the conductive hearing loss and check for other conditions that may be causing the hearing loss. Persistent effusion after 3 months of medical therapy is an indication for surgery, particularly when associated with hearing loss or tympanic membrane changes. Surgery consists of a myringotomy with placement of a ventilation tube. This procedure is usually done under local anesthesia in the office. The tube typically falls out spontaneously in several months. The results are excellent but the patient must keep moisture out of the ear (e.g., avoid swimming) until healing is complete, which usually takes 6 to 18 months.
Acute Otitis Media
Patients with acute suppurative otitis media complain of marked pain in the ear and most give a history of a recent upper respiratory infection. Drainage of purulent material from the ear indicates probable tympanic membrane perforation or concomitant otitis externa. On examination, there is injection and loss of luster of the tympanic membrane, grayish-pink coloration of the entire membrane, and, eventually, bulging of the membrane and loss of landmarks. Some patients have a conductive hearing loss demonstrated by tuning fork tests (see Preliminary Hearing Testing and Table 110.2). There may be tenderness to palpation of the mastoid bone because the mucosa lining of the mastoid cells is continuous with that of the middle ear. Evidence of otitis externa is usually not present. The most common etiologic agents are S. pneumoniae (Pneumococcus), Haemophilus influenza, and Moraxella catarrhalis(10,11). Although some cases are caused by viral pathogens, diagnosis of these cases is usually not practical and treatment should be the same for all patients with acute otitis media.
Medical treatment consists of systemic antimicrobials for 10 days. The antibiotic course should be completed to avoid recurrent or persistent infection and mastoiditis. Amoxicillin, 500 mg three times daily for 10 days, remains the drug of first choice. The growing prevalence of β-lactamase–producing bacteria may necessitate the use of amoxicillin–clavulanate (Augmentin 250/125 or 500/125 tablets), cefuroxime axetil (Ceftin 250 or 500 mg tablets) or clindamycin (Cleocin 300 mg tablets) as second line antimicrobial choices. For penicillin-allergic patients, erythromycin, cefuroxime axetil, and trimethoprim-sulfamethoxazole (TMP-SMX) (e.g., Bactrim, Septra, or generic) may be used. Aspirin, acetaminophen, or ibuprofen every 4 to 6 hours should be recommended for pain. If perforation with discharge occurs, Cortisporin otic suspension, four drops three times daily for 1 week, may be added to the treatment. If the tympanic membrane is bulging with pus and the patient describes severe pain or vertigo, myringotomy by an otolaryngologist is indicated to prevent extension of the infection and resultant complications.
Close followup is recommended within a week of starting therapy to ensure a normal response to treatment. Recovery from the pain of acute otitis media is usually prompt. Pain and fever should be absent by 3 days of therapy. If not, alternative antibiotics should be prescribed with followup within a few days. Within 1 to 4 weeks, hearing impairment should resolve and the tympanic membrane assumes its normal appearance. Serous otitis may be present after other signs and symptoms of acute otitis have resolved. In the patient who notes persistent otalgia, fever, or other signs of toxicity despite adequate antibiotics for 48 hours, subacute mastoiditis should be suspected, and prompt referral to an otolaryngologist is indicated. Facial nerve dysfunction, vertigo, and signs of central nervous system (CNS) infection likewise require prompt evaluation and management. Frequent recurrence of otitis media, failure of serous otitis to resolve, persistence of a tympanic membrane perforation, and significant persistent hearing loss after 4 to 6 weeks are all indications for referral so that potential serious underlying pathology can be ruled out.
Barotrauma
Barotrauma refers to symptoms and signs produced by a sudden pressure differential between the middle ear and the surrounding atmosphere. The patient gives a history of fullness, pain, and decreased hearing in one or both ears. This problem is most commonly associated with descents while flying or scuba diving. Otoscopic findings vary from mild tympanic membrane retraction to hemotympanum, with or without perforation. There may be conductive or neurosensory hearing loss. Any patient with moderate or severe unilateral hearing loss should be referred to an otolaryngologist because of the possibility of inner ear involvement. For patients with mild symptoms, topical or
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oral decongestants may alleviate symptoms. Prophylaxis against barotrauma consists of use of the Valsalva maneuver and chewing gum or swallowing during descent in airplanes, and management of allergic conditions involving the upper respiratory tract.
Temporal Bone Fractures
Traditional classification of the lateral skull base is based on the orientation of the fracture line in relation to the long axis of the temporal bone (petrous pyramid). Knowledge of the fracture line orientation predicts the extent of middle- and inner-ear damage and the pattern of cranial nerve injury. Eighty percent of temporal bone fractures are longitudinal, most often caused by blows to the lateral skull (13). Longitudinal fracture follow the long axis of the temporal bone coursing along at 45-degree angle from the external meatus toward the postnasal chamber. The plane of fracture extends along the external ear canal to involve the ossicular chain (to produce a conductive hearing loss) and occasionally the facial nerve. Transverse temporal bone fractures extend perpendicularly to the long axis of temporal bone, crossing the inner ear (to produce a sensorineural hearing loss) and often the facial nerve. Transverse fractures account for approximately 20% of temporal bone fractures. Evaluation of a temporal bone fracture requires a careful otoscopic and cranial nerve evaluation, supplemented by high-resolution computerized tomography (CT) scanning. Treatment is dictated by sequelae of the fracture.
Traumatic Perforation of Tympanic Membrane
A tympanic membrane perforation may be caused by a cotton-tipped swab or other object for removing wax, foreign bodies, forcefully directed water, and blast waves resulting from detonation of high explosives. Symptoms include decreased hearing, tinnitus, pain, and bleeding. Otoscopic examination reveals a perforation, commonly in the area of the pars tensa (Fig. 110.2). Air insufflation, which aids in the diagnosis, especially if a perforation is suspected but not seen, shows an immobile tympanic membrane.
The objective of treatment is the prevention of infection. Most linear tears and small perforations of the membrane heal spontaneously in several weeks. Large perforations may require grafting by an otolaryngologist. This procedure is usually done under general anesthesia as an outpatient procedure. A piece of temporal fascia is used for the patch. The results are highly successful with minimal postoperative discomfort. If there is a strong possibility that the middle ear has been contaminated at the time of injury, oral antibiotics (ampicillin or erythromycin 250 mg four times daily for 1 week) are indicated. Patients should prevent water or other contaminants from entering the ear by the insertion of a petroleum jelly-covered cotton plug. Swimming should be avoided altogether. Patients whose perforation was self-inflicted should be warned against future syringing and probing to remove cerumen.
After spontaneous closure or myringoplasty, the hearing loss caused by perforation usually resolves completely. Within a few months the perforation or surgical repair is no longer visible, although occasionally a thin area or a whitish scar remains. Tinnitus, sensorineural hearing loss, and vertigo are signs of inner ear injury and necessitate prompt referral to an otolaryngologist, who will evaluate the patient for a fistula, which requires prompt repair.
Chronic Otitis Media
Chronic otitis is present when a patient has otorrhea, either persistent or recurrent, and there is perforation of the tympanic membrane and usually some degree of conductive hearing loss. The management of this problem has two objectives: eradication of infection and restoration of hearing. When chronic otitis media is initially recognized, the patient should be referred to an otolaryngologist for evaluation (14).
Chronic otitis media can be divided into two major subgroups: inactive and active. Table 110.4 summarizes the
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clinical characteristics of these two groups. The fundamental difference in the active subgroup is the presence of, or potential for, bone destruction caused by invasion by squamous epithelium known as cholesteatoma. Cholesteatoma occurs when squamous epithelium of the auditory canal invades the middle ear through a preexisting perforation (acquired cholesteatoma). The cholesteatoma appears as a mass of keratinaceous debris that accumulates at the site of invasion of squamous epithelium. As the mass enlarges, it carries the potential to erode bone and promote further infection. Facial paralysis caused by cranial nerve VII involvement, meningitis, and brain abscess may occur as a complication of active cholesteatoma.
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TABLE 110.4 Chronic Otitis Media: Features Distinguishing Inactive and Active (Cholesteatoma) Forms |
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The commonly performed surgical procedures for chronic otitis media are described below.
These operative procedures are usually done as outpatient surgical procedures. General anesthesia is usually required for both types of mastoidectomy, whereas the plasty procedures can most often be done with only local anesthesia. There is moderate discomfort for 2 to 3 days. However, for 4 to 6 weeks after any of these procedures, the patient must avoid heavy lifting, strenuous exercise, or any similar activity that could result in a Valsalva maneuver, which results in the increase of air pressure in the middle ear and may disrupt the repair. The success rate of all these procedures is approximately 80%.
Complications of Otitis Media
Acute or chronic suppurative otitis media may become complicated by extension of infection beyond the confines of the middle ear into bone and other surrounding structures. These complicating infections are mastoiditis, facial nerve paralysis (caused by cranial nerve VII involvement), petrositis (inflammation of the petrous portion of the sphenoid with diplopia, pain around the eye, and persistent otorrhea), labyrinthitis, brain abscess, extradural abscess, subdural abscess, lateral sinus thrombophlebitis, meningitis, and otitic hydrocephalus. Symptoms not attributable to the typical course of acute or chronic otitis media may signify the presence of one of these complications and require immediate referral and hospitalization.
Ossicular Chain Problems
The most common of these (adhesive otitis media and tympanosclerosis) occur as sequelae to otitis media. Others (ossicular injury or otosclerosis) may affect the ossicular chain in the absence of a history of or signs of prior otitis media. Ossicular chain problems may be recognized by demonstrating conductive hearing loss (usually chronic, either unilateral or bilateral). Changes of the tympanic membrane indicative of prior otitis media may or may not be present, depending on the problem. In some conditions, otoscopy may even be diagnostic. Each of these conditions requires referral to an otolaryngologist for accurate diagnosis and consideration of surgical management.
Adhesive Otitis Media
There is a history of ear infection, and the tympanic membrane is retracted and atrophic in areas of healed perforations. The eardrum is usually draped over the promontory and incudostapedial complex. Adhesive otitis media is usually a late complication seen in patients with persistent middle ear inflammation. Hearing loss is usually mild, although some patients may require ossicular reconstruction or a hearing aid (see Hearing Aids).
Tympanosclerosis
There is a history of infection, often bilateral. There is usually, but not always, a tympanic membrane perforation, and discrete plaques of dense collagen with calcified hyaline may be seen in the middle ear. In selected patients tympanic membrane and ossicular reconstruction is necessary to improve hearing.
Traumatic Ossicular Injury
There is a history of trauma (e.g., temporal bone fracture and the causes of traumatic perforation listed above) followed by unilateral hearing loss, which may be conductive or mixed. A hemotympanum (blood behind the eardrum) is usually seen, although occasionally the tympanic membrane is normal. Hearing status after surgical exploration depends on the type of injury found at surgery.
Otosclerosis
Otosclerosis is a disease of the labyrinthine capsule in which spongelike bone is laid down, causing fixation of the stapes and conductive hearing loss, usually bilateral. The history discloses a slowly progressive hearing loss. Onset is usually in the late teens to thirties, but occasionally in the forties. It is seen more commonly in females (F-to-M ratio 2:1). It is often accelerated by pregnancy. From 50% to 70% of cases are hereditary, following an autosomal dominant mode of inheritance. History is key in establishing the diagnosis because examination of the tympanic membrane is usually normal. This is the most
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common cause of progressive conductive hearing loss in young adults. The results of surgery, consisting of stapedectomy or stapedotomy and prosthetic replacement, are excellent.
New Growths of Middle Ear
A number of benign and malignant growths may be seen on inspection of the tympanic membrane of patients with progressive unilateral conductive hearing loss. Malignant tumors most commonly present with a history of chronic discharge, occasionally bloody.
Chronic Sensorineural Hearing Loss
Presbycusis
A certain degree of hearing loss, beginning in the high-frequency range, is universal among elderly people. Most do not complain of deafness, and often a family member is the first to notice the hearing deficit. Clearly, social and psychological factors are important in determining the level of reported disability. For this reason, in the general population of elderly, in whom hearing loss is common, screening of asymptomatic patients using an office audiogram is not usually recommended because obtaining a hearing aid (see Hearing Aids), the usual prescription, is expensive and cumbersome and most patients will not use one until they have perceived their hearing problem and seek a remedy on their own. Instead the U.S. Preventive Services Task Force recommends periodically questioning elderly patients about their hearing, counseling them about the availability of hearing aid devices, and making referrals for abnormalities when appropriate (http://www.ahrq.gov/clinic/uspstfix.htm).
When an older patient is first found to have moderate hearing loss, the patient and family should be counseled as outlined below (seeDealing with The Patient with Permanent Hearing Loss), and the patient offered a referral for evaluation by an audiologist (see Audiometry, above) or by an otolaryngologist (15).
Noise-Induced Hearing Loss
Noise-induced hearing loss is a form of sensorineural hearing loss commonly found in patients employed in high-noise industries or exposed to intense noise from power tools, firearms, and other sources (16). Loud rock music also may cause hearing loss, but because of the range of sound it is a slower process, often occurring 10 to 15 years after repeated exposure. Like presbycusis, it is initially a high-frequency hearing loss, eventually involving lower frequencies. Prophylaxis by wearing muffs and earplugs in high-noise settings and reducing noise levels are the best ways to prevent acoustic trauma. Established hearing loss caused by noise is usually irreversible, but progressive hearing loss can be prevented. Acute hearing loss caused by an acute episode of acoustic trauma, such as gunfire or cordless telephone ringer accidents (a loud sound or shock caused by electrical surge), is often reversible and referred to as a temporary threshold shift.
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TABLE 110.5 Drugs That May Cause Sensorineural Hearing Loss |
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Drug-Induced Hearing Loss
A number of drugs may produce bilateral sensorineural hearing loss, and the patient's personal physician often is the first to learn of this problem (Table 110.5). For most of these drugs, ototoxicity is dose related; however, hearing impairment may occur even at therapeutic dosages. A mild hearing loss occurs in as many as 10% of patients whose serum levels of gentamicin and tobramycin are maintained within the therapeutic range (17).
The prognosis for drug-induced hearing loss varies according to the drug. Salicylates in high dosages and quinine usually produce temporary, high-frequency deafness, but permanent deafness has been reported in patients surviving salicylate poisoning and in infants of mothers who received quinine during pregnancy. Aminoglycoside ototoxicity may occur suddenly after a few doses, may be permanent, and may progress after discontinuation of the drug. Diuretic-induced ototoxicity may be seen after extremely high dosages, usually in patients with renal insufficiency. Its onset may be sudden, after intravenous (and rarely oral) administration, and the hearing deficit may be permanent.
Ménière Syndrome
Ménière syndrome is characterized by spells of a constellation of otologic symptoms. Symptoms are thought to be caused by endolymphatic hydrops manifested by excess fluid and pressure in the cochlea and vestibular labyrinth. Ménière attacks consist of fluctuant hearing loss, roaring tinnitus, aural fullness, and spontaneous peripheral-pattern vertigo (see Chapter 89). However, in many
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instances the disorder produces a nonclassic array of symptoms. An attack may last for minutes to an hour, often with nystagmus present on physical examination. Between attacks, tinnitus and sensorineural hearing loss often persist. Symptoms are unilateral in 70% to 80% of cases (18). The hearing loss and vertiginous episodes may occur simultaneously, or in tandem. Vertigo may be accompanied by nausea and emesis. In severe episodes, other vagal symptoms may occur, including pallor and sweating and rarely bradycardia. Audiometry demonstrates sensorineural hearing loss, predominantly in lower frequencies in early stages of the disease.
The differential diagnosis of Ménière syndrome includes a number of conditions that may also present with hearing loss and vertigo unrelated to position change: viral laby-rinthitis, acoustic neurinoma, syphilitic vertigo, labyrin-thine fistula, vestibular granuloma, temporal bone fracture, or multiple sclerosis (see Chapter 89 for details regarding vertigo).
Treatment
Patients with suspected Ménière syndrome should be referred promptly to an otolaryngologist to confirm the diagnosis and initiate treatment. Patients are placed on a low sodium diet (<2,000 mg/day) and are treated empirically with diuretics, 25 to 50 mg of hydrochlorothiazide daily or its equivalent, with attention to avoid hypokalemia (see Chapter 50). The antihistamine meclizine can be tried in a dosage of 25 mg three to four times daily, but often this fails to prevent attacks of vertigo. For nausea, the patient should take the antiemetic prochlorperazine either as a 5- or 10-mg capsule four times daily, or as a 25-mg suppository twice daily. After the acute attack has subsided, the patient should continue diuretic treatment; after 1 year without recurrence, diuretic treatment can be discontinued. For the occasional patient with severe recurrent Ménière syndrome refractory to medical treatment, several surgical procedures offer high response rates. Treatment with intratympanic injection of gentamicin can be beneficial when vertigo persists despite optimal medical management, which may be required in an estimated 10% of patients. Surgical ablation of the vestibular labyrinth is required to control vertigo symptoms in an extremely small percentage of patients (19).
Prognosis
Ménière disease tends to be chronic and progressive, but fluctuates unpredictably. Acute attacks of vertigo often increase in frequency during the first few years after presentation, then decrease in frequency and cease. Symptoms other than hearing loss improve in 60% to 80% of people irrespective of treatment (20). However, there is sustained loss of hearing. In the minority of patients who develop second ear, contralateral involvement, the disease generally manifests less severe symptoms.
Acoustic Neuroma
Acoustic neuroma, an uncommon, benign tumor, usually arises from the vestibular fibers of nerve VIII. It grows slowly, expanding within the internal auditory meatus until it is large enough to extend into the posterior fossa and compress adjacent structures of the CNS. Essentially all patients present with symptoms of eighth nerve impairment: unilateral, usually chronic hearing loss is found in the majority of patients. Most frequently, patients will note a progressive inability to discriminate speech on the telephone using the involved ear. Tinnitus and chronic, usually mild, positional vertigo or sense of imbalance occurs in many patients. Audiometry usually demonstrates significant sensorineural hearing loss with poor discrimination of speech. Neurologic examination (see Chapter 86) shows involvement of the following neurologic structures, in decreasing order of frequency: cranial nerves VIII, V, VII, VI, and cerebellum (ataxia, with tendency to fall toward the side of the lesion). Referral to an otolaryngologist for evaluation is essential whenever unilateral sensorineural hearing loss is initially found. Diagnosis of acoustic neuroma is based on a characteristic audiogram or other audiologic or vestibular findings, but must be either ruled out or confirmed with magnetic resonance imaging of the internal auditory canal and posterior fossa (Fig. 110.6) (21). The results of surgical treatment generally permit the patient to resume usual activity, but often with permanent unilateral hearing loss (22). In a few patients with good hearing preoperatively, it may be possible to preserve hearing. Stereotactic radiation of acoustic neuromas offers a treatment option that is noninvasive. Radiation is designed to induce a fibrotic response of the tumor capsule with the goal of controlling tumor growth. Treatment using radiation is generally employed for tumors in patients with medical conditions that preclude surgery.
Sudden Sensorineural Hearing Loss
Sudden sensorineural hearing loss, usually unilateral, is an otologic emergency. The cause is often difficult to ascertain and may include viral cochleitis, arterial occlusion (especially in patients with other evidence of arterial occlusive disease, such as embolic transient ischemic attacks), inner ear fistula, autoimmune factors (23), sudden expansion of a cerebellopontine angle tumor (e.g., a meningioma or acoustic neuroma, see Acoustic Neuroma), temporal bone fracture, and noise trauma. Symptoms, which occur over a matter of minutes to hours, include tinnitus or
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hearing loss. After prompt evaluation for conductive hearing loss (including simple cerumen impaction), these patients should be referred immediately for evaluation by an otolaryngologist. A number of empirical medical therapies (e.g., corticosteroids, vasodilators, membrane-deforming agents, or anticoagulants) have been tried with varying success. Most recently, the use of intratympanic dexamethasone administered via transtympanic injection has shown promise in treating sudden, idiopathic sensorineural hearing loss, particularly if administered within days of the onset of the loss (24). For patients with suspected inner ear fistulas, surgical exploration may be necessary.
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FIGURE 110.6. MRI of internal auditory canals and posterior fossa demonstrating a right-sided vestibular schwannoma (acoustic neuroma) marked with asterisk. The tumor demonstrates 2.3 cm extension from the (expanded) porous acousticus of the internal auditory canal into the cerebellopontine angle, placing the patient at risk for cranial neuropathies and increased intracranial pressure as a consequence of pontomedullary brain stem compression (T1 image with gadolinium enhancement). |
Most patients have permanent, severe unilateral hearing loss, and they and their families should be instructed about adequate noise protection for the only hearing ear, preferential seating for optimal use of the good ear, and precautions when driving to compensate for missed sound cues.
Tinnitus
Tinnitus (“ringing”) is the perception of sounds in the absence of a normal sound stimulus. Intermittent tinnitus is common in the general population. Persistent tinnitus may be caused by a number of identifiable problems. Occasionally, tinnitus may be experienced only at night, in bed, when ambient noise is reduced.
Subjective Tinnitus
The term subjective tinnitus is used when the subject complains of noises that cannot be heard by the observer. Subjective tinnitus may be subdivided into two types.
Tympanic tinnitus usually arises as a result of a conductive lesion (all of the causes of conductive hearing loss, Table 110.3). It is thought to be caused by removal of the normal masking effect of ambient noise, with emergence of otherwise subaudible tympanic, vascular, and muscular noises. The patient often describes the tinnitus as pulsating.
Petrous tinnitus is caused by conditions affecting the cochlea or eighth nerve that lead to sensorineural hearing loss (Table 110.3). It is attributed to recognition of auditory stimuli produced by mechanical cochlear deformation or hyperirritability of the acoustic nerve. It may be intermittent or continuous with varying intensity.
After the patient's primary otologic problem has been defined, the most important requirement in helping the patient with tinnitus is reassurance because patients may believe that their tinnitus reflects a serious intracranial condition. Bedtime sedation to ensure adequate sleep is important. Some patients also find that the sound of an FM radio (FM delivers a broader range of frequencies, particularly in the higher spectrum than AM) helps them get to sleep by competing with the more distressing sounds caused by tinnitus. For patients with severe tinnitus, masking treatment (an apparatus that externally generates white noise and is available from an audiologist) may be helpful. Recently developed digital music players can be especially helpful for masking. The distressing nature of severe and chronic tinnitus has resulted in the development of tinnitus clinics and support groups in most large cities (25). The critical role of tricyclic antidepressants in managing patients with coexisting disabling tinnitus and depression is now well established (26).
Objective Tinnitus
Objective tinnitus is a noise audible to the examiner and originates from the region of the patient's ear. Causes include aneurysm of the internal carotid artery, benign vascular tumors of the middle ear, temporomandibular joint instability, and myoclonus of the palatal muscles. Although not audible by the examiner, a complaint of pulsatile tinnitus may also indicate benign intracranial hypertension. These patients should be referred to an otolaryngologist for a diagnostic workup. Also, patients with tinnitus that lateralizes to one ear should also be referred for further evaluation.
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Dealing with the Patient with Permanent Hearing Loss
Communication
Counseling of the family and others who speak to the patient with moderate to severe hearing loss should emphasize the following points.
For the patient with profound or total hearing loss, the principle governing all communication is that the patient must see the message. Most patients let the physician know the mode of communication they prefer (lip reading or writing). Whenever there is any question about the effectiveness of lip reading, written exchange of information should be used. This can be facilitated by ensuring that paper and a pen or pencil are always available to the patient. The use of a word processor program with large font is particularly helpful in facilitating communication with deaf patients. When sign language is the preferred mode of communication, arrangements should be made in advance for an interpreter to be present at appointments. Also, various devices are now available, although they are moderately expensive, that make it possible for totally deaf people to receive telephone calls (messages are entered by the sender in code on a touch-tone unit and displayed visually for the deaf receiver) and to follow television programs. Many people who are totally deaf at an early age learn sign language, and programs for learning sign language are widely available. Valuable information to help people with any level of hearing impairment may be obtained from Self-Help for Hard of Hearing People, Inc., http://www.SHHH.org, and The A.G. Bell Association for the Deaf and Hard of Hearing, http://www.AGBell.org.
Hearing Aids
Hearing aids (miniature, battery-powered microphone–amplifier–loudspeaker units) can assist the patient with sensorineural hearing loss and patients with irreversible conductive loss (27). The currently available aids include in-the-ear, delicate, and behind-the-ear units. Older devices were incorporated into eyeglasses or carried in a pocket with a wire connection to the ear mold. Hearing aids can increase the intensity of a sound by up to 70 dB. Thus, a sound of about 60 dB (the level of average conversational speech) passing through an aid may enter the ear at a level of 130 dB. This represents the maximal usable gain of an aid because sounds above this level become painful.
Federal law now prevents the sale of hearing aids to people who have not been evaluated first by a physician. Only trial and adjustment determine whether a patient referred for a hearing aid will benefit. Medicare and other third-party insurers do not pay for hearing aids and they are expensive, typically costing over 600 dollars. Most hearing aid dealers allow a 30-day trial period during which the patient pays a rental fee; some states require this by law. Currently, only a minority of people who would benefit from a hearing aid own one, usually because of the cost and the difficulty or embarrassment perceived in using it. Also, many who own units do not use them regularly because of difficulty in using them or the presence of irritating sounds, which often can be eliminated by adjustment of the device by an audiologist.
Patients may mention certain specific problems with the hearing aid to their personal physicians. There may be irritation of the conchal cartilage, infection in the external canal, or an increase in cerumen accumulation. In each of these situations, the fitting audiologist should evaluate use of the aid. A better fitting mold is needed to avoid recurrence in some patients. Others may do well by removing the aid periodically during the day.
Amplification devices have evolved considerably in the past decade. Digital hearing aids convert electronic sound information from the microphone into a digitized code, which is then processed by an amplifier consisting of microchips instead of electronic circuitry. All adjustments are programmed using computer software. Substantially more expensive, the primary advantage of digital signal processing is the greater processing power than prior analog signal processors in the hearing aid. The greater processing power represents greater decision making ability by the instrument, allowing many more adjustments and greater precision of adjustments for the listener to make according to the acoustic environment.
For selected patients, semi-implantable systems including implantable bone conduction aids and cochlear implants are now available (28). The cochlear implant is used in patients who are unable to derive significant benefit from the use of powerful hearing aids. Young deaf children who are appropriately managed with cochlear implants demonstrate an increased likelihood of gaining access to mainstream education opportunities (29). Deaf adults with previous experience with verbal language also enjoy significant changes in quality of life as a result of increased access to the spoken word (30).
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Specific References*
For annotated General References and resources related to this chapter, visit http://www.hopkinsbayview.org/PAMreferences.