Fitting Strategies for Patients with Conductive Or Mixed Hearing Loss

12843.C10.PGS 3/8/02 11:12 AM Page 272

Fitting Strategies for Patients with Conductive or Mixed Hearing Loss

JOEL GOEBEL, MICHAEL VALENTE, MAUREEN VALENTE, JANE ENRIETTO, KAREN M. LAYTON, MARK S. WALLACE

Introduction Bone conduction aids were once the mainstay of amplification technology for CHL. Surgical correction of conductive hearing These bone conduction devices, however, loss (CHL) is the principal and preferred have been superseded by newer technology treatment by most patients. Surgical therapy [i.e., bone-anchored hearing aid (BAHA®)]. is successful in the majority of cases, but not The use of conventional or programmable all patients are candidates for surgery be- air-conduction aids and implantable bone- cause of medical, anatomic, or personal rea- conduction hearing devices is emphasized sons. Although most who undergo an oto- in this chapter. logic operation achieve socially adequate There are a variety of causes of hearing hearing [i.e., speech recognition threshold loss. It is important for all members of the (SRT) of 25-dB hearing level (HL) or less], hearing health care team (otolaryngologists, some do not, and these patients can gener- audiologists, and aural rehabilitation spe- ally obtain additional benefit from amplifica- cialists) to fully understand the mechanisms tion. In cases of CHL in only hearing ear, the of both conductive and sensorineural com- surgeon recommends amplification to avoid ponents in each individual case and develop the risk of surgical complications that might an optimal rehabilitative strategy. In cases increase the hearing loss, provided that the with a significant conductive component, CHL is not the result of a progressive disor- many factors must be weighed. Certain der, such as a cholesteatoma. Thus, amplifi- physical findings such as persistent otor- cation for CHL remains a topic of great inter- rhea, cholesteatoma, and mass lesions of the est to audiologists, otologists, and patients external and middle ear require aggressive alike. medical and surgical therapy regardless of This chapter discusses the types of CHL the degree of conductive impairment. In for which amplification is the primary other cases with congenital or progressive treatment method, those for which amplifi- disorders resulting in CHL, the main issues cation is fitted secondarily following recov- are the degree of hearing impairment, the ery from surgery, and those for which com- age of the patient, the status of the other ear, bined surgical-audiologic treatment (i.e., and the probable success of surgery versus implantable hearing device) is warranted. amplification.

272 12843.C10.PGS 3/8/02 11:12 AM Page 273

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 273

This chapter first outlines the various migration of cerumen. Some patients suffer causes of CHL and then reviews the medical, from excessive collections of squamous de- surgical, and rehabilitative options. bris that forms a plug or cast of the EAC. If the process does not erode the skin or bone of the EAC, the term keratosis obturans ap- Lesions of the External Auditory Canal plies. In cases of canal erosion, a canal wall Any process that obstructs the external audi- cholesteatoma is suspected. Periodic re- tory canal (EAC) can result in a CHL up to moval of the debris is indicated and possible 40-dB HL. These lesions can be separated surgical widening and grafting of the EAC is into congenital or acquired etiologies. Congen- performed in severe cases (Farrior, 1990). ital stenosis (narrowing) or atresia (failure to Tumors of the external canal may be either develop) of the EAC may be partial or com- malignant or benign and either soft tissue or plete and is frequently accompanied by de- bony. Keratinous cysts of the EAC are com- formities of the pinna, ossicles, middle ear mon and warrant surgical removal if they cavity, and otic capsule, resulting in a wide obstruct the canal. Malignant tumors include range of hearing loss from mild conductive squamous cell, basal cell, melanoma, cerumi- loss to severe mixed loss. High-resolution noma, and tumors of the parotid gland in- computed tomography (CT) scan of the tem- vading the EAC. Surgical therapy is the main poral bone is necessary to evaluate the extent treatment for these lesions. Acquired bony of bony versus soft tissue stenosis, the shape lesions include exostoses and osteomas, which of the ossicular chain, and the presence or ab- are also removed when they obstruct the sence of an aerated (air-containing) middle canal or trap wax and debris (Fisher and ear space. Surgical reconstruction of the EAC McManus, 1994). and ossicular chain is warranted as early as Chronic external otitis may lead to pro- possible in cases of bilateral stenosis with CT gressive narrowing of the external canal with evidence of middle ear aeration and normal subsequent hearing loss. Aggressive topical otic capsule anatomy (Chandrasekhar et al, steroid and antimicrobial therapy is neces- 1995). In cases of unilateral disease, patients sary, with surgical treatment reserved for are usually advised to reach adulthood be- cases of soft tissue stenosis (Parisier and Lev- fore making a decision regarding surgery. enson, 1991). The use of hearing aids in these Amplification strategies include bone-conduc- cases is contraindicated because of the aggra- tion hearing aids and bone-anchored hearing aids vation of the inflammation caused by the de- (BAHAs) in cases where reconstruction of the vice in the EAC. EAC and ossicular chain is impossible. These two treatment plans are discussed later in this chapter. Lesions of the Tympanic Membrane Acquired obstruction of the EAC is com- Tympanic Membrane Perforation monly caused by cerumen impaction, collec- tion of squamous (skin) debris, tumors, or Perforations of the tympanic membrane chronic external otitis (infection) with steno- cause a variable amount of CHL based on sis. Periodic cerumen removal in the office the size and location of the perforation and under direct vision is required in certain pa- the presence or absence of otorrhea. Small tients with excessive cerumen production or (1 to 2 mm) dry perforations generally cause small, tortuous external canals. Self-manipu- minimal hearing loss (in fact, this is essen- lation of the canal (i.e., cotton swabs) is not tially identical to the placement of a pres- recommended due to the possibility of in- sure-equalizing tube). Larger perforations jury to the canal skin or tympanic mem- with chronic mucoid otorrhea centered more brane. This problem is especially bother- posteriorly tend to cause more CHL in the some in patients wearing hearing aids that 25- to 35-dB HL range. Total tympanic mem- occlude the canal and prevent the normal brane perforations can result in CHL of 12843.C10.PGS 3/8/02 11:12 AM Page 274

274 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

40-dB HL or greater. When the perforation is ate CHL. Placement of long-standing PE posterosuperior, extends to the margin of tubes for ventilation is the mainstay of ther- the tympanic membrane, and collects squa- apy (Mandel et al, 1989). Chronic otorrhea via mous debris, a cholesteatoma is suspected a TM perforation is common and precludes that may cause ossicular erosion and hear- the use of a hearing aid until the drainage ing loss as great as 60-dB HL. is stopped via medication or tympanomas- In most cases, surgical repair of the perfo- toid surgery. Finally, ossicular continuity is ration is recommended and is successful in frequently disrupted at the incudostapedial about 90% of cases with near-complete clo- joint, resulting in CHL from 15- to 50-dB HL. sure of the air-bone gap (Glasscock, 1973). In In these cases, ossiculoplasty with bone or a small percentage of cases, surgical failure synthetic prostheses is indicated with vari- or late reperforation occurs due to poor eu- able success (Brackmann et al, 1984). In many stachian tube function. In such cases, ampli- instances, amplification is necessary due to a fication is indicated as long as the perfora- persistent conductive loss or an accompany- tion is dry. ing sensorineural component.

Tympanosclerosis Cholesteatoma Tympanosclerosis is the accumulation of As mentioned above, cholesteatoma is an dense hyaline-like material in the fibrous aggressive invasion of squamous epithelium layer of the tympanic membrane. This results into the middle ear and mastoid spaces. Al- in stiffening of the tympanic membrane and though not truly neoplastic, the squamous may impede sound transmission. In severe cells incite a cascade of inflammatory media- cases, the ossicular chain is also involved. tors that trigger bony resorption involving Surgical management is warranted when a the ossicles, mastoid cells, and even the otic perforation is also present; otherwise, ampli- capsule. In all cases, surgical removal or ex- fication is recommended to overcome the teriorization of all cholesteatoma matrices is CHL. necessary to achieve a dry ear (Parisier et al, 1991). When this is done, then either surgical Adhesive Otitis Media reconstruction of the ossicular chain or amplification can be achieved. Cholesteatoma In certain cases of severe eustachian tube is an aggressive process with serious com- dysfunction, the tympanic membrane (TM) plications and therefore must be treated collapses into the middle ear space. A mod- aggressively. erate conductive loss is common and surgical attempts to graft the TM with fascia or Otosclerosis cartilage and placement of a pressure equal- ization (PE) tube are variably successful. In Otosclerosis is a progressive osteodystrophy such cases, amplification is recommended to (abnormal bone growth) of the otic capsule rehabilitate the ear. that most frequently involves the anterior stapedial footplate, causing fixation and progressive CHL. The disease is thought to be Lesions of the Middle Ear and Mastoid inherited in an autosomal-dominant pattern with variable penetrance, although alterna- Chronic Otitis Media tive theories implicating viral infections have Chronic infections of the middle ear can re- been reported. The disease usually becomes sult in damage to the tympanic membrane, evident in the third decade of life and may ossicular chain, and even cochlear hearing be bilateral. Audiometric findings include via the round window. In cases of chronic oti- a low- to midfrequency conductive loss from tis media with effusion (COME), a tenacious 10- to 50-dB HL, elevation of the 2000-Hz mucoid effusion persists that causes a moder- bone threshold (Carhart notch), normal or 12843.C10.PGS 3/8/02 11:12 AM Page 275

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 275

stiff tympanogram, and absent stapedial re- and should be suspected in any cases of per- flexes. Options for therapy include observa- sistent otorrhea unresponsive to antimicro- tion and serial audiometry, surgery, or ampli- bial therapy. A mixed hearing loss can result fication. Observation is warranted if the CHL if untreated and amplification may be un- is slight (<20-dB HL) and the patient is fully successful in severe cases. functional in his or her environment. Surgery consists of either total removal of the stapes Surgery to Provide Amplification (stapedectomy) or partial footplate fenestra- tion (stapedotomy) and piston reconstruc- Surgery for providing amplification is an tion of the ossicular chain (Rizer and Lippy, emerging area of interest. As mentioned, 1993). The decision of stapedectomy versus surgical modification of the external audi- amplification is based on a combination of tory canal for congenital or acquired atresia severity of loss, age and occupation of the is a standard procedure. In recent years, patient, and discussion of the risks of surgi- electromagnetic devices have been devel- cal intervention. In general, younger, active oped that are either coupled to the ossicular patients desire surgical treatment, whereas chain directly or vibrate the skull, thereby the elderly patient frequently decides to pur- eliminating the mechanical issues of sound sue amplification. Surgery is contraindicated transduction via the air through the external in an only-hearing ear or in patients with se- canal and tympanic membrane. Such de- vere vertigo. Success rates up to 95% are re- vices are desirable in patients with (1) atresia ported for closure of the 500 to 2000 Hz air- not amenable to surgical reconstruction, (2) bone gap to within 10-dB HL (Rizer and persistent otorrhea due to chronic suppura- Lippy, 1993). In patients who are undecided, tive otitis media resistant to medical and a trial with amplification is useful, reserving surgical therapy, (3) uncorrectable ossicular surgery for those patients who fail. abnormalities, or (4) intolerance or allergy to earmolds. Suitable candidates meeting the medical and audiologic criteria for such de- Tumors of the Middle Ear and Mastoid vices should have realistic motivation and A variety of benign and malignant tumors understanding of the benefits and limita- can affect the middle ear and mastoid, re- tions. Contraindications include (1) the ab- sulting in a conductive hearing loss. A thor- sence of suitable ossicular or squamous tem- ough workup, including CT scan imaging, poral bone in which to place the device and magnetic resonance imaging (MRI), angiog- lack of adequate skin cover, (2) active in- raphy, and surgical exploration, is necessary fection in the implantation site, and (3) to eliminate these lesions. Amplification is systemic disease that might affect wound reserved to rehabilitate the resultant con- healing. Some of these fitting options are ductive loss produced by the lesion and its discussed later in this chapter. The option of removal. middle ear implants (MEIs) are covered in great detail in Chapter 11. Inflammatory Diseases of the Middle Ear and Mastoid Overall Strategies for Amplification Because the middle ear and mastoid are The optimal strategy for hearing restoration lined with respiratory epithelium, these requires an individualized approach based spaces are also prone to systemic inflamma- on many factors. Active infection of the exter- tory processes that affect the entire respira- nal canal, tympanic membrane, or middle ear tory tract. Examples of such diseases include must be medically or surgically controlled be- Wegener’s granulomatosis, sarcoidosis, and fore amplification is prescribed. Surgical cor- amyloidosis. These diseases can cause a clin- rection of dry tympanic membrane perfora- ical picture similar to chronic otitis media tions, ossicular discontinuity, or ossicular 12843.C10.PGS 3/8/02 11:12 AM Page 276

276 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

fixation is recommended with amplification equipment)]. The Classic 300 is capable of reserved for residual conductive or mixed connecting directly to assistive-listening de- losses after surgery. One exception would be vices (FM, infrared, Walkman devices, etc.) the poor surgical candidate where amplifica- via direct auditory input (DAI). Finally, the tion is the only alternative. In cases of severe Classic 300 can be ordered with a telecoil, au- aural atresia or uncontrolled chronic otitis ditory adapter, and directional microphone. media with an open mastoid cavity, surgi- The Compact operates on a 13 battery and has cal implantation of electromagnetic bone- a volume control/on/off switch, tone control anchored devices may be warranted. In many [N (normal-frequency response), L (high-fre- instances patients may progress through quency attenuation), and E (disconnects the stages in their disease process that include all microphone so the Compact can be directly medical, surgical, and rehabilitative options. coupled to external equipment)] switch. The Compact is capable of connecting directly to assistive listening devices (FM, infrared, Implantable Bone-Conduction Walkman devices, etc.) via DAI. Finally, the Hearing Device Compact can be ordered with a telecoil and In the first edition of this textbook, the au- auditory adapter. The Cordelle II operates on thors included information on the Xomed a rechargeable 9V battery and, as mentioned Audiant implantable hearing aid as a treat- earlier, provides about 13 dB greater gain than ment option for patients with conductive or the Classic 300. This unit has a built-in telecoil mixed hearing loss. Unfortunately, this (M/T/MT switch), tone switch for low- and product was removed from the market in high-frequency attenuation, and K-AmpTM the late 1990s due to its inability to provide signal processing where the compression adequate gain/output for many patients kneepoint and loudness boost can be ad- with conductive or mixed hearing loss. Since justed. the first edition was published, the BAHA® These devices transmit amplified sound has been introduced. It has been approved directly to the skull without interference by the Food and Drug Administration (FDA) from the intermediate tissue. The BAHA® as a treatment option for patients with con- consists of a titanium fixture that is an- ductive or mixed hearing loss where the chored into the skull and a percutaneous ti-

bone-conduction pure-tone average (BCPTA tanium abutment that is attached to the tita- at 500, 1000, 2000, and 3000 Hz) is 45-dB HL nium fixture and penetrates the skin (Fig. or better and who are at least 5 years old. 10–2). Finally, a processor is connected to the Currently, the BAHA® is available in the protruding part of the abutment (Fig. 10–2). Classic 300 (upper drawing in Fig. 10–1) and With the BAHA®, no tissue is present to Cordelle II (lower drawing in Fig. 10–1). Re- impede the transmission of the amplified cently, the BAHA® became available as a sound, and the processor does not press Compact smaller device (i.e., 35% smaller than against the skin and cause irritation. the Classic 300). All three processors are available in beige, black, and gray. The Cordelle II Surgical Considerations provides about 13 dB greater output than the Classic 300 and the Compact and is typically The titanium screw and abutment is typi- utilized for those patients who report that the cally implanted using general anesthesia gain provided by the Classic 300 or Compact on an outpatient basis. A skin flap is ele- is insufficient. The Classic 300 operates on a vated and thinned to the appropriate thick- 675 battery and has a volume control/on/off ness as necessary. A suitable location on the switch and tone control switch [N (normal- skull above and behind the pinna is chosen. frequency response), L (high-frequency atten- Drilling begins with a 3-mm and then 4-mm uation), and E (disconnects the microphone so fixed-depth guide drill. A larger center hole the 300 can be directly coupled to external is drilled with a countersink drill in prepara- 12843.C10.PGS 3/8/02 11:12 AM Page 277

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 277

Figure 10–1. Drawing of the bone-anchored hearing aid (BAHA®) Classic 300 (upper) and Cordelle II (lower) sound processors. Upper: (1) volume control; (2) tone switch; (3) electrical input; (4) battery compartment; (5) battery cover; (6) microphone; (7) abutment snap; (8) attachment for safety line; (9) gain control; (10) tone control (bass cut); (11) serial number. Lower: (1) transducer; (2) body worn unit; (3) cord; (4) M-MT-T switch; (5) electrical input; (6) tone switch; (7) volume control; (8) microphone; (9) electrical output; (10) trim controls; (11) clip; (12) battery cover; (13) battery compartment; (14) serial number; (15) abutment snap; (16) electrical input; (17) serial number. (From Entific Medical Systems, with permission.)

tion for threading. The internal device is a Cordelle II) can be connected and discon- titanium fixture (Fig. 10–2) that is mounted nected at will via an abutment snap [items in the bone behind the ear where it osseo- 7 (upper) and 15 (lower) in Fig. 10–1] on the integrates. The vibrations from the sound Classic 300 or Cordelle II. The bone screw processor are transmitted to the fixture via becomes osseointegrated over 3 (for adults) a percutaneous abutment (Fig. 10–2). The to 6 months (for children) and becomes sound processor (Classic 300, Compact, or rigidly coupled with the skull. The external 12843.C10.PGS 3/8/02 11:12 AM Page 278

278 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

Figure 10–2. BAHA® titanium fixture, titanium abutment and hearing aid. (From Entific Med- ical Systems, with permission.)

sound processor is typically fit 8 to 10 weeks Patients with bone conduction thresh- postoperatively. The sound processor trans- olds between 25- and 45-dB HL can ex- forms vibrational energy in the skull, caus- pect improvement, but may not achieve ing the cochlea to vibrate. Because of the aided levels within in the normal range rigid coupling, the sound transfer is excel- of hearing. Patients who bone conduc- lent, especially at the higher frequencies, tion thresholds are less than 25-dB HL where speech understanding occurs. could have restored aided hearing levels within the normal range. 2. Has an air-conduction word recogni- Postoperative Care tion score in quiet [at 30-dB sound level Postoperative care is minimal. In the imme- (SL) or at a most comfortable loudness diate postoperative period, antibiotic oint- level] of greater than 60%. ment and dressing changes are done. Once 3. Is free from a generalized disease process the sutures are removed and wound healing that could result in poor wound healing. is complete, no continuing attention is nec- 4. Is unwilling or unable to be a candidate essary. Patients are advised to examine the for reconstructive surgery. area periodically for evidence of irritation. 5. Is unable to use conventional air- or Routine assessment after healing is typi- bone-conduction hearing aids because cally unnecessary. Daily cleaning is essen- of chronic otitis media, congenital mal- tial after healing to maintain proper healing. formation of the external/middle ear, or Ninety-eight percent of problems with the other acquired malformations of the ex- BAHA® are due to recurring infections of ternal or middle ear that preclude wear- the skin. ing conventional air-conduction aid. 6. Is strongly motivated toward this surgical procedure. Audiologic Criteria for the BAHA® 7. Is able to understand the objectives and expectations of this method of amplifi- Patients for whom no better alternative treat- cation. ment exists may be considered candidates 8. Is psychologically and emotionally sta- for the BAHA® if the aided ear: ble to maintain the hygiene of the per-

1. Has a BCPTA at 500, 1000, 2000, and 3000 cutaneous titanium abutment. that is equal to or better than 45-dB HL. 9. Is at least 5 years old. 12843.C10.PGS 3/8/02 11:12 AM Page 279

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 279

Examples of pathologies or conditions that frequency hearing through more direct bone may lend themselves to the BAHA® include: conduction. Another advantage is stable bone vibrator placement through surgical implan- 1. Congenital or acquired atresia of external tation rather than external placement of the canal or middle ear that is not amenable bone vibrator on the skin over the mastoid, to surgical reconstruction. which is subject to movement. 2. Stenosis of the ear canal. 3. Chronic suppurative otitis media that is resistant to medical-surgical therapy. Fitting Strategies for the BAHA® 4. Complications from radical mastoidec- If the results of the audiometric examination tomies. establish that a patient meets the selection cri- 5. Congenital or acquired ossicular mal- teria described above, then the patient should formations. be counseled about the BAHA® and referred 6. Severe tympanosclerosis. to the otolaryngologist. Assuming that all cri- 7. Postoperative mastoid cavity with teria have been met, the audiologist and oto- chronic otorrhea. laryngologist would determine the processor 8. History of intolerance or allergy to ear- (Classic 300, Compact, or Cordelle II) that ap- molds. pears most appropriate. As discussed earlier, this decision would depend primarily on the bone-conduction thresholds and the subjec- Advantages of the BAHA® over the tive judgments of the patient. A test head- Bone-Conduction Hearing Aid band (Fig. 10–3) is available to determine Prior to the introduction of implanatable hear- which ear would be the best candidate for ing aids, bone-conduction hearing aids (to surgical placement of the titanium fixture. All be described later in this chapter) were the three processors can be attached to the head- hearing aids typically fit on patients with con- band. The headband can be useful to deter- ductive or mixed hearing loss. Advantages mine on which side the titanium fixture of the BAHA® over a bone-conduction hear- should be implanted. Additional information ing aid include the absence of pressure on the may include onset of the hearing loss (i.e., skin from the headband, elimination of feed- congenital vs. acquired) and prior experience back, reduced distortion, and improved high- with amplification.

Figure 10–3. BAHA® test headband. (From Entific Medical Systems, with permission.) 12843.C10.PGS 3/8/02 11:12 AM Page 280

280 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

According to manufacturer guidelines, the that over 68% reported no skin reactions processor is fit after 3 to 4 months in adults (e.g., swelling or redness around the abut- and 6 months in children. This allows for ment; granulation; removal/revision). An complete osseointegration of the titanium additional 21% had one or two episodes of fixture and abutment. At approximately 6 adverse reactions. Five of the patients lost months postimplant (2 to 3 months after the their abutment due to direct trauma (e.g., initial fitting), the audiologist would evalu- hitting a doorway; blow to the ear; taking off ate the performance of the BAHA® by hav- an apron), and an additional five patients ing the patient face a loudspeaker at 1 m at lost osseointegration of the implant. That is, 0-degree azimuth. Now, the audiologist in 90% of the patients (90/100), the BAHA® would assess the unaided performance as was still intact following surgery over an well as the aided performance of the 8-year time frame. Tjellstrom and Granstrom BAHA® and the patient’s air- and/or bone- (1995) reported on 214 patients who were conduction aids. Measures would include: followed over a 5-year period using a two- stage (titanium screw implanted first and 1. Warble tone thresholds at 500, 1000, then titanium abutment attached at a second 2000, 3000, and 4000 Hz. surgery) or one-stage (titanium screw and ti- 2. Word recognition for monosyllabic tanium abutment implanted at the same time) words presented at 63-dB SPL and surgical procedure. These authors reported speech-shaped noise presented at 57-dB that the success rates for both procedures SPL [a +6 dB signal-to-noise ratio (SNR)]. were the same. In the two-stage group, 3. Completion of the preoperative [12 nearly 68% had no adverse reactions to the questions about the performance of the implant, and the number increased to nearly patient’s current aid(s)] and postopera- 75% of the one-stage group. Tjellstrom and tive (eight questions about the perfor- Hakansson (1995) reported that in 806 obser- mance of the BAHA®) questionnaires. vations, 96.4% of the cases indicated no ad- Expected performance with the BAHA® verse reaction to the surgical procedure. is improving the aided warble tone thresholds to within normal limits if the unaided Subjective Outcomes bone-conduction thresholds were better than 25-dB HL and close to the normal range Hakansson et al (1990) reported that 22 of 24 if the bone conduction thresholds were subjects reported fewer ear infections with the between 26- and 45-dB HL. In addition, the BAHA® than their previous air-conduction speech recognition in noise performance hearing aids (ACHAs). Also, 16 of 24 (67%) with the BAHA® should be significantly subjects reported better sound quality with better than unaided and with the patient’s the BAHA® in comparison to their AC hear- current aid(s). Finally, the subjective prefer- ing aids, and 19/27 (70%) other subjects who ence for BAHA® should be rated signifi- were experienced bone-conduction hearing cantly better than the patient’s current aid(s). aid (BCHA) users reported greater comfort Optimally, patients will also report im- with the BAHA® (four reported no differ- proved fidelity and reduced feedback rela- ence and four reported poorer comfort with tive to the performance of their air- and/or the BAHA®). bone-conduction hearing aid. Tjellstrom and Hakansson (1995) reported on 122 cases from nine sites on a questionnaire for unaided, BAHA®, and BCHA Research Findings Using the BAHA® listening conditions. On the questionnaire, 86.6% reported they use the BAHA® 8 or Surgical Outcomes more hours/day. The subjects also reported Tjellstrom and Granstrom (1977) reviewed that the BAHA® resulted in improved over 100 BAHA® cases from 1977 and found speech intelligibility, better sound comfort, 12843.C10.PGS 3/8/02 11:12 AM Page 281

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 281

less pressure on the head, less skin irritation, BAHA® at 500 Hz. For the SRT, the BAHA® easier handling, and greater cosmetic accep- and the BCHA reported a mean improve- tance than the BCHA. In addition, 44 of ment over unaided performance by 26.5-dB 51 subjects (86%) reported a general im- HL. For word recognition in noise, the provement of their ear infections after they BAHA® improved word recognition, on av- switched to the BAHA® in comparison to erage by 41.8%, whereas the BCHA improved those who previously had worn air conduc- word recognition, on average, by 35.5% (i.e., tion hearing aids. Finally, 55 of 67 subjects BAHA® better than the BCHAs by 6.2% and 82%) reported improved wearing comfort in found to be statistically significant, p <0.001). comparison to their previous BCHA. See the additional readings at the end of this chapter for more references on the surgical, subjective, and objective outcomes re- Objective Outcomes ported with the BAHA®. Tjellstrom and Hakansson (1995) reported on 122 cases from nine sites using sound- Hearing Aid Selection and Fitting field warble tone thresholds (500 to 3000 for Conventional Hearing Aids Hz), SRTs, and word recognition at +6-dB SPL (signal at 63-dB SPL; speech noise at Options for selecting and fitting hearing aids 57-dB SPL). The mean improvement for for conductive or mixed hearing loss can the BAHA® over the unaided hearing was generally be divided into three categories. As 29.4-dB HL (range of 26.0- to 36.3-dB HL), illustrated in Figure 10–4, patients can be fit- whereas the mean improvement for the ted with air conduction in-the-canal (ITC, BCHA was 27.3-dB HL. The advantage of left), in-the-ear (ITE, center), or behind-the- the BAHA® over the BCHA ranged between ear (BTE, right) hearing aids. Patients can be 1.6 and 9.1 dB, where the mean improve- fit with eyeglass-, body-, or bone-conduction ment for the BCHA was better than the hearing aid(s). Finally, patients can receive

Figure 10–4. Examples of three air conduction hearing aids. Left: In-the-canal (ITC) hearing aid. Middle: In-the-ear (ITE) hearing aid. Right: Behind-the-ear (BTE) hearing aid. 12843.C10.PGS 3/8/02 11:12 AM Page 282

282 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

an implanted bone-conduction hearing de- Libby, 1986) does not specifically provide vice as was discussed in the previous section. such guidelines. For example, if a patient has a 65 dB sensorineural hearing loss at 2000 Hz, the National Acoustic Laboratories re- Air-Conduction Hearing Aids vised (NAL-R) procedure advocated by Determining which air-conduction hearing Byrne and Dillon (1986) prescribes 26 dB of aid is most appropriate is usually based on real-ear gain. If the patient had a mixed hear- (1) the magnitude of hearing loss, (2) the ing loss at 2000 Hz with an air-bone gap of 45 magnitude of the air-bone gap, and (3) pa- dB, the prescribed gain would be increased tient preference. As a general rule, as the to 37 dB (i.e., 26-dB sensorineural hearing hearing loss and magnitude of the air-bone loss and 11 dB to compensate for 25% of the gap increases, the need to fit a BTE or body 45-dB air-bone gap). If the audiologist, how- hearing aid increases. Finally, air-conduction ever, were fitting to the Berger et al formula, hearing aids should be considered the most the recommended gain would be 50 dB (i.e., appropriate fitting for chronic conductive 42 dB for the 65-dB sensorineural loss and 9 hearing loss when medical contraindications dB to compensate for 20% of the 45-dB air- have been ruled out. bone gap with a maximum of 8 dB).

Fitting Strategies for Air-Conduction Verification Strategies for Air- Hearing Aids Conduction Hearing Aids Regardless of the type of air-conduction The verification process for air-conduction hearing aid, the appropriate real-ear gain for hearing aids can either be real-ear gain using patients with conductive or mixed hearing probe tube or functional gain measures loss can be determined by using many of the (see Chapter 3), paired comparisons (see prescriptive procedures reported in Chap- Chapter 4), and/or subjective evaluations ters 1 and 3. That is, prescribed real-ear gain (see Chapter 5). for hearing aids providing linear amplification is based on the air-conduction threshold Bone-Conduction Hearing Aid with additional gain prescribed to compensate for the magnitude of the air-bone gap. Bone-conduction hearing aids are available in Lybarger (1955, 1963), Byrne (1983), and BTE and in eyeglass (Fig. 10–5) and body (Fig. Byrne and Dillon (1986) recommend that 10–6) configurations. Bone-conduction aids 25% of the air-bone gap should be added to are the most appropriate hearing aid fitting the amplification requirements for patients when it is physically impossible to use air- with sensorineural hearing loss. On the conduction hearing aids. Examples of such other hand, Berger et al (1984) recommend circumstances may be atresia, severe stenosis that 20% of the air-bone gap should be of the ear canal, chronic middle ear drainage, added with the maximum additional gain and chronic allergic reaction to the materials limited to 8 dB at any frequency. used to manufacture earmolds. In addition, it Other than Berger et al (1984) and Byrne is important that bone-conduction thresholds and Dillon (1986), no prescriptive formulas are within normal limits or only slightly re- described in Chapters 1 and 3 specify guide- duced in order to achieve success with this lines for providing additional gain to com- type of amplification. Finally, it is important to pensate for the air-bone gap. The authors feel remember that conventional bone-conduction that audiologists should always consider hearing aids should be evaluated and fitted on at adding between 20% and 25% of the air-bone least a trial basis prior to fitting an implantable gap to the prescribed gain even if the se- bone-conduction hearing device. lected prescriptive procedure (Cox, 1983, Bone-conduction hearing aids deliver the 1988; McCandless and Lyregaard, 1983; amplified sound to a bone vibrator that is 12843.C10.PGS 3/8/02 11:12 AM Page 283

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 283

Figure 10–5. Example of an eyeglass bone-conduction hearing aid.

Figure 10–6. Example of bone conduction vibrator attached to a headband and body hearing aid. 12843.C10.PGS 3/8/02 11:12 AM Page 284

284 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

placed over the mastoid process. The vibra- referred to Chapter 2 in Hearing Aids: Stan- tor is held in place by a headband or eye- dards, Options and Limitations, 2nd edition glass frame. The most frequently used bone- (Thieme Medical Publishers) for a compre- conduction hearing aids are eyeglass and hensive overview of the improved isolation body designs. The eyeglass arrangement is currently available in hearing aids. The audi- typically preferred for cosmetic reasons and ologist is urged to view these previous should be initially recommended even if the guidelines with some skepticism and to eval- patient has normal vision and will use non- uate, at least on a trial basis, air-conduction prescription lenses. The use of bone-conduc- hearing aids for patients in whom air-bone tion hearing aids is limited due to both mini- gaps exceed 40 dB HL. mal available gain at 3000 to 4000 Hz and As with air-conduction hearing aids, the difficulties involved in achieving the precise primary strategy for bone-conduction hear- placement and tension of the vibrator on the ing aids in cases of conductive and/or mastoid process. In addition, many patients mixed hearing loss is to reduce or eliminate using bone-conduction hearing aids com- the air-bone gap. Again, the most appropri- plain of headaches and soreness around the ate fitting strategy is to determine the pre- mastoid process due to the pressure of the scribed real-ear gain using many of the pre- bone vibrator on the mastoid process. Despite scriptive procedures outlined in Chapters 1 these drawbacks, successful bone-conduction and 3 with additional gain to compensate for fittings have been achieved by the authors the air-bone gap. Finally, like conventional air- because of our access to optometrists and op- conduction hearing aids, bone-conduction ticians who have experience in the proper hearing aids should be fit bilaterally when ap- placement of the bone vibrator. To the best of propriate (see Chapter 7). the authors’ knowledge, only Starkey Labo- ratories have eyeglass bone-conduction hear- Verification Strategies ing aids available for dispensing to patients with conductive or mixed hearing loss. The verification process for bone-conduction fitting is primarily limited to measures of functional gain (see Chapters 1 and 3). Re- Fitting Strategies cently, paired comparisons (see Chapter 4) Lybarger (1955, 1963) provides guidelines and subjective evaluations (see Chapter 5) that suggest that if the air-bone gap is <25- have become increasingly popular to verify dB HL, then a conventional air-conduction the fitting of hearing aids for patients with hearing aid is the appropriate fitting. If sensorineural hearing loss. The use of paired the air-bone gap is between 25- and 40-dB comparisons and subjective evaluations HL, then either an air-conduction or bone- could be extended to fittings for patients conduction fitting may be appropriate. Fi- with conductive or mixed hearing loss. Real- nally, if the air-bone gap is >40-dB HL, then ear probe tube measures are not commonly a bone-conduction fitting may be the most used as a means to verify bone-conduction appropriate. To the authors’ knowledge, fittings. however, Lybarger’s recommendations have never been evaluated clinically, and the Summary guidelines do not consider cases in which the air-bone gap may be different at different Surgical correction of most conditions caus- frequencies within the same ear. In view of ing conductive hearing loss provides satisfac- recent advances in earmold and hearing aid tory results. Amplification plays an impor- technology (improved isolation between tant role in cases in which the postoperative transducers within the hearing aid case, hearing level is suboptimal and in cases in for example), it is now possible to achieve which surgery is not possible or appropriate. greater gain without feedback. The reader is The various otologic conditions causing con- 12843.C10.PGS 3/8/02 11:12 AM Page 285

CHAPTER 10 FITTING STRATEGIES FOR CONDUCTIVE OR MIXED HEARING LOSS 285

ductive hearing loss were reviewed, and the Rizer F, Lippy W. Evolution of techniques of stapedectomy from the total stapedectomy to the small fenes- interaction of surgery and amplification were tra stapedectomy. Otolaryngol Clin North Am 1993; discussed. 26:443–451. Depending on the circumstances, air con- Tjellstrom A, Granstrom G. Long-term follow-up with the bone-anchored hearing aid: a review of the first duction, bone conduction, or the BAHA® 100 patients between 1977 and 1985. ENT J 1994; may be used. The indications, contraindica- 73(2):21–23. tions, and criteria for their use were discussed. Tjellstrom A, Granstrom G. One-stage procedure to establish osseointegration: a zero to five years follow- up report. J Laryngol Otol 1995;109:593–598. Tjellstrom A, Hakansson B. The bone anchored hearing aid: design, principles, indications and long-term References clinical results. Otolaryngol Clin North Am 1995;28(1): 53–72. Berger K, Hagberg WN, Rane RL. Prescription of Hearing Aids: Rationale, Procedures, and Results, 4th. ed. Kent, OH: Herald Press, 1984. Brackmann D, Sheehy J, Luxford W. TORPs and PORPs Additional Readings: BAHA® in tympanoplasty: a review of 1042 operations. Arch Otolaryngol Head Neck Surg 1984;92:32–37. Bonding P, Jonsson M, Ahlgren P. The bone-anchored Byrne D. Theoretical prescriptive approaches to select- hearing aid: osseointegration and audiological ef- ing the gain and frequency response of a hearing fect. Acta Otolaryngol Stockh Suppl 1992;492:42–45. aid. Monogr Contemp Audiol 1983;4:1–40. Browning G, Gatehouse S. Estimation of the benefit of Byrne D, Dillon H. The National Acoustics Laboratory bone-anchored hearing aids. Ann Otol Rhinol Laryn- (NAL) new procedure for selecting the gain and fre- gol 1994;103:872–878. quency response of a hearing aid. Ear Hear 1986;7: Burell S, Cooper H, Proops D. The bone-anchored hear- 257–265. ing aid, the third option for otosclerosis. J Laryngol Chandrasekhar S, De la Cruz A, Garrido E. Surgery of Otol Suppl 1996;21:13–20. congenital aural atresia. Am J Otol 1995;16:713–717. Carlsson P, Hakansson B. The bone-anchored hearing Cox R. Using ULCL measures to find frequency/gain aid: reference quantities and functional gain. Ear and SSPL90. Hear Instrum 1983;34:17–22. Hear 1997;18:34–41. Cox R. The MSU hearing instrument prescription proce- Carlsson P, Hakansson B, Ringdahl A. Force thresholds dure. Hear Instrum 1988;39:6,81. for hearing by direct bone conduction. J Acoust Soc Farrior J. Cholesteatoma of the external ear canal. Am Am 1995;97:1124–1129. J Otol 1990;11:113–116. Chasin M. Current trends in implantable hearing aids. Fisher E, McManus T. Surgery of external canal exos- Trends Ampl 1997;2(3):83–107. toses and osteomata. J Laryngol Otol 1994;108:106– Chasin M. Update on implants: bone anchored devices 110. and middle ear implants. Hear J 1999;52(7):10,12,14, Glasscock ME. Tympanic membrane grafting with fas- 16–17. cia: overlay versus underlay technique. Laryngoscope Chasin M, Wade P. Bone anchored hearing aids (BAHA) 1973;83:754–770. and unilateral conduction losses. Hear Rev 1998;5(8): Hakansson B, Liden G, Tjellstrom A, et al. Ten years of 34–43. experience with the Swedish bone anchored hearing Cremers C, Snik A, Beynon A. Hearing with the bone- system. Ann Otol Rhinol Laryngol 1990;99(10)(suppl anchored hearing aid (BAHA HC 200) compared to 151), part 2. conventional to a conventional bone-conduction Libby ER: The 1/3–2/3 insertion gain hearing aid selec- hearing aid. Clin Otolaryngol 1992;17:275–279. tion guide. Hear Instrum 1986;37:27–28. Hakansson B, Carlson P. Skull simulator for direct bone Lybarger SF. Basic Manual for Fitting RadioEar Hearing conduction hearing devices. Scand Audiol 1989;18: Aids. Pittsburgh, PA: Radioear Corp., 1955. 91–98. Lybarger SF. Simplified Fitting System for Hearing Aids. Hakansson B, Carlson P, Tjellstrom A, Liden G. The Canonsburg, PA: Radioear Corp., 1963. bone-anchored hearing aid: principal design and au- Mandel E, Bluestone C, Paradise J. Myringotomy with diometric results. ENT J 1994;73:670–675. and without tympanoplasty tube insertion in the Hakansson B, Tjellstrom A, Rosenhall U, Carlsson P. treatment of chronic otitis media with effusion. Arch The bone-anchored hearing aid: principal design Otolaryngol Head Neck Surg 1989;115:1217–1224. and a psychological evaluation. Acta Oto Laryngol McCandless GA, Lyregaard PE. Prescription of gain/ Stockh 1990;100:229–239. output (POGO) for hearing aids. Hear Instrum 1983; Hartland S, Proops D. Bone anchored hearing aid wear- 34:16–20. ers with significant sensorineural hearing loss (bor- Parisier S, Levenson M. Surgical management of the derline candidates): patients’ results and opinions. external auditory canal. In: AAO-HNS Instructional J Laryngol Otol Suppl 1996:21:41–46. Courses. 1991, pp. 280–298. Jensen J, Salomon G, Bonding P. The bone-anchored Parisier S, Weiss M, Edelstein W. Treatment of hearing aid-measurements of the clinical function. cholesteotoma. In: Myers B, Bluestone C, Brack- J Audiol Med 1993;2:175–187. mann D, Krause E, eds. Advances in Otolaryngology- Liepert D, DiToppa J. The Nobel pharma auditory sys- Head and Neck Surgery, vol 5. St. Louis: Mosby Year tem bone-anchored hearing aid: the Edmonton ex- Book, 1991, pp. 107–141. perience. J Otolaryngol 1994;23:411–418. 12843.C10.PGS 3/8/02 11:12 AM Page 286

286 STRATEGIES FOR SELECTING AND VERIFYING HEARING AID FITTINGS

McNamara M, Philips D, Proops D. The bone-anchored in terms of sound quality and speech intelligibility. hearing aid (BAHA) in chronic suppurative otitis Br J Audiol 1995;29:299–307. media (CSOM). J Laryngol Otol Suppl 1996;21:38–40. Snik A, Mylanus E, Cremers C. Speech recognition with Mylanus E, Cremers C. A one stage surgical procedure the bone anchored hearing aid determined objec- for placement of percutaneous implants for the bone tively and subjectively. ENT J 1994;73:115–117. anchored hearing aid. J Laryngol Otol 1994;108:1030– Snik A, Mylanus E, Cremers C. Bone-anchored hearing 1033. aids in patients with sensorineural hearing loss and Mylanus E, Cremers C, Snik F, van den Berge N. Clinical persistent otitis externa. Clin Otolaryngol 1995;20: results of percutaneous implants in the temporal 31–35. bone. Arch Otolaryngol Head Neck Surg 1994;120:81–85. Snik A, Mylanus E, Cremers C. The bone-anchored Mylanus E, Snik A, Cremers C. Patients’ opinions of hearing aid compared with conventional hearing bone-anchored vs conventional hearing aids. Arch aids: audiologic results and the patients’ opinions. Otolaryngol Head Neck Surg 1995;121:421–425. Otolaryngol Clin North Am 1995;28:73–83. Mylanus E, Snik A, Cremers C, Jorritsma F, Verschuure Snik A, van der Pouw C, Beynon A, Mylanus E, Cre- I. Audiological results of the bone anchored hearing mers C. Binaural application of the bone-anchored aid HC200, multicentre results. Ann Otol Rhinol hearing aid. Ann Otol Rhinol Laryngol 1998;107:187– Laryngol 1994;103:368–374. 193. Mylanus E, Snik A, Jorritsma F, Cremers C. Audiologi- Stephens D, Board T, Hobson J, Cooper H. Reported cal results of the bone anchored hearing aid HC200. benefits and problems experienced with bone- Ear Hear 1994;15:87–92. anchored hearing aids. Br J Audiol 1996;30:215–220. Mylanus E, van der Pouw C, Snik A, Cremers C. An in- Tjellstrom A, Granstrom G. One-stage procedure to es- traindividual comparison of the BAHA and ACHAs. tablish osseointegration: a zero to five-years follow- Arch Otolaryngol Head Neck Surg 1998;124:271–276. up report. J Laryngol Otol 1995;109:593–598. Papsin B, Sirimanna T, Albert D, Bailey M. Surgical Tjellstrom A, Rosenthal U, Lindstrom J, Hallen O, experience with bone-anchored hearing aids in chil- Albrektsson T, Branemark P. Five-year experience dren. Laryngoscope 1997;107:801–806. with skin-penetrating bone-anchored implants in Ringdahl A, Eriksson-Mangold M, Israelsson B, Sand- the temporal bone. Acta Otolaryngol 1983;95:568– strom G. Perceived sound quality of three bone- 575. anchored hearing aid models. Br J Audiol 1995;29: Van der Pouw C, Snik A, Cremers C. Audiometric 309–314. results if bilateral bone-anchored hearing aid appli- Ringdahl A, Isrealsson B, Caprin L. Paired comparisons cation in patients with bilateral congenital aural between the classic 300 bone-anchored hearing aid atresia. Laryngoscope 1998;108:548–553.