Verification of Speech Spectrum Audibility for Pediatric Baha Softband Users with Craniofacial Anomalies

Abstract

Objective

The purpose of this study was (1) to determine benefit of the Baha Softband coupled to the Softband for infants and children with bilateral conductive hearing loss; and (2) to verify audibility of the speech spectrum for octave frequencies 500 through 4000 Hz.

Design

The research design for this retrospective chart study is pretest-posttest repeated measures.

Setting

The study was conducted in the Department of Audiology and Speech Pathology, Arkansas Children's Hospital.

Participants

Twenty-five children aged 6 months to 18 years with craniofacial disorders and bilateral conductive hearing loss participated in the study. Participants were consistent, full-time unilateral Baha users with the Baha Compact bone-conduction amplifier coupled to the head via the Softband.

Interventions

The intervention was the Baha device coupled to the head via the Softband as a prerequisite to surgical implantation.

Main Outcome Measure(s)

The primary study outcome measures used aided and unaided soundfield audiometric thresholds to calculate functional gain. Audibility of the speech spectrum was verified by comparison with target aided thresholds.

Results

Results revealed an improvement in soundfield thresholds with Baha amplification for the four octave frequencies. Means, standard deviations, and confidence intervals for aided and unaided thresholds are reported. Percentages of thresholds meeting target levels were significant at all frequencies, exceeding the 80% criterion.

Conclusions

Benefit of the Baha in providing audibility of the speech spectrum for infants and children with bilateral congenital conductive hearing loss has been demonstrated, offering important and timely data supporting third-party reimbursement.

Keywords

audibility Baha craniofacial hearing loss verification

The inherent risk of unidentified hearing loss in children with cleft palate and other craniofacial anomalies is the subsequent delay in speech and language development that can occur without early, appropriate, and timely intervention. It is well established that children with these conditions have an increased likelihood of associated conductive and/or sensorineural hearing loss and, as such, are frequently identified early; however, the challenge of providing intervention to allow audibility of the speech spectrum remains challenging (Joint Committee on Infant Hearing [JCIH], 2007). Until recently, intervention options using amplification technology have been limited to conventional bone-conduction devices with metal headbands for infants and children who are surgical risks, presurgical patients, and/or for those in whom surgical correction is not indicated. The Baha device, coupled to the head via a Softband offers another viable solution (Hol et al., 2005).

Many of the multi-anomaly disorders with characteristic craniofacial anomalies and/or cleft palate (e.g., Treacher Collins syndrome, Robin sequence, 22q11.2 microdeletion syndromes) involve structural malformations of the outer ear and/or middle ear resulting in a conductive hearing loss. Other craniofacial conditions (e.g., Crouzon syndrome, oculoauriculovertebral spectrum) may include combined involvement of outer, middle, and inner ear structures, resulting in a mixed hearing loss. Although a comprehensive review of craniofacial disorders associated with conductive and/or mixed hearing loss is beyond the scope of this article, some general comments regarding the most common associated disorders serve to inform the reader about characteristics, pathophysiology, and typical audiometric profiles.

Audiologic profiles of craniofacial disorders with and without cleft palate commonly associated with conductive hearing loss have been characterized for Treacher Collins (Pron et al., 1993), Apert (Rajenderkumar et al., 2005), and Crouzon syndromes (Orvidas et al., 1999; Vallino-Napoli, 1996) in addition to Robin sequence (Handzic et al., 1995), 22q11.2 microdeletion (Solot et al., 2000), and oculoauriculovertebral spectrum (Rahbar et al., 2001; Vendramini, 2007). Familiarity with these profiles can contribute important information to help guide decision making when considering intervention options.

Treacher Collins syndrome, also called mandibulofacial dysostosis, affects the head and face. Characteristics include downward slanting palpebral fissures, malar hypoplasia, micrognathia, and malformed ears (Jones, 2006). In 1993, Pron and colleagues described the hearing loss and ear pathology in a cohort of 29 individuals with Treacher Collins. They reported external ear canal abnormalities as typically symmetric, either bilaterally stenotic or atretic. In most cases, the middle-ear cavity was bilaterally hypoplastic and dysmorphic, and ossicles were symmetrically missing or absent. Hearing-loss configurations were either flat or reverse sloping with a pure tone average ranging from 44 to 62 dB hearing level (HL).

Apert syndrome is a condition involving irregular craniosynostosis, midfacial hypoplasia, syndactyly, and broad distal phalanx of thumb and big toe. In 2003, Rajenderkumar and colleagues provided a report on the audiological profile of the syndrome. They reviewed 70 patients, reporting that almost all had a history of otitis media with effusion that tended to persist into adulthood. In addition, they reported that more than 56% of their patients developed permanent low-frequency conductive hearing loss by 10 to 20 years of age.

Crouzon syndrome is characterized by craniosynostosis, maxillary hypoplasia, shallow orbits, and ocular proptosis. Orvidas and colleagues (1999) described audiometric findings of a cohort of 19 patients with Crouzon syndrome. Although all patients had normal-sized pinna, six (32%) had low-set ears; of these, three had malpositioned ears (posteriorly rotated). One patient (5%) had bilateral external auditory canal atresia; whereas, another was noted to have stenotic canals. Ten patients (53%) had a history of recurrent otitis media, two patients had conductive hearing loss without a history of otitis media, one patient had a mixed hearing loss with a malformed and fixed incus, and another had a unilateral conductive hearing loss attributed to a high-riding jugular bulb on that side.

Some conditions are not classified as a syndrome, but rather as a sequence or spectrum. The term sequence describes a condition in which a single problem in morphogenesis leads to a cascade of subsequent defects (Jones, 2006). Robin sequence is one such condition and is characterized by a wide, U-shaped cleft palate and a small lower jaw with the tongue positioned toward the back of the mouth. Handzic and colleagues (1995) reported hearing levels for a cohort of 18 participants with Robin sequence compared with 243 patients with cleft palate. They concluded that hearing loss in patients with Robin sequence is usually bilateral, conductive, and occurs more frequently (30 ears or 83.33%) than in patients who have cleft palate but do not exhibit the Robin sequence (290 ears or 59.67%). However, due to the diverse etiologies that are included in this population, one must use caution when making generalizations about type and degree of hearing loss.

Spectral disorders are those in which a broad sequence or range of related qualities are exhibited. Deletion 22q11.2 syndrome is among the most clinically variable syndromes with more than 180 features associated with the deletion (Robin and Shprintzen, 2005). Key characteristics associated with 22q11.2 deletion include congenital heart disease, palatal abnormalities, renal anomalies, and hearing loss (Digilio et al., 2005). Velocardiofacial syndrome and DiGeorge syndrome represent two different manifestations or points along the continuum of the same genetic disorder (Driscoll et al., 1992a; Driscoll et al., 1992b; Burn and Goodship, 1993; Driscoll et al., 1993; Goldmuntz et al., 1993; Matsouka et al., 1994; McDonald-McGinn et al., 1995; Jones, 2006). In 1999, Digilio and colleagues reported on a cohort of 47 children with 22q11.2 deletion, 39% of whom demonstrated conductive (n = 18) or mixed (n = 1) hearing loss in one or both ears. Etiologies were attributed primarily to ossicular abnormalities; although, some were attributed to complications of chronic otitis media with effusion.

A second spectral disorder is oculoauriculovertebral spectrum. In 2007, Rahbar and colleagues evaluated the clinical, audiologic, and temporal bone computed tomographic findings in patients with this disorder. The OMENS grading system (O = orbital asymmetry; M = mandibular hypoplasia; E = auricular deformity; N = nerve involvement; S = soft tissue deficiency) was used to classify the five most common associated dysmorphic manifestations. Mandibular hypoplasia and auricular abnormalities were the most common clinical manifestations, present in 39 patients (97%) and 38 patients (95%), respectively. Conductive hearing loss was reported in 35 patients (86%) and sensorineural hearing loss, in four patients (10%). Facial nerve weakness was present in 20 patients (50%). Twenty patients had unilateral aural atresia, 12 had unilateral aural stenosis, and seven had bilateral anomalies. Moderate hypoplasia or atresia of the auditory canal was noted in 36 patients (90%), and ossicles were malformed in 30 patients (75%).

The Baha system is a viable, surgically implantable amplification option to consider for children with bilateral congenital conductive and/or mixed hearing loss. First introduced in 1977 (Tjellström and Håkansson, 1995), it received approval by the Food and Drug Administration (FDA) (FDA, 1995) for use with conductive and mixed hearing loss in 1996 and for pediatric patients older than 5 years of age in 1999. In 2001, the FDA approved it for bilateral implantation, and in 2002 for use with unilateral or single-sided deafness (an assumption is made that this applies to children 5 years of age and older). The Baha implant system consists of an external component (sound processor and abutment) and an internal component (small titanium implant). The external component connects percutaneously to the internal component when implanted in the skull bone behind the ear. This provides an alternative pathway for sound to reach the brain, via bone conduction instead of air conduction, as with traditional hearing aids.

If a child has a condition resulting in a permanent conductive hearing loss, that child may be a candidate for a Baha implant (Nicholson, 2006); however, children younger than 5 years of age (current FDA regulations) cannot be implanted with the device (unless they are part of a clinical trial conducted in the United States). In contrast, in Europe, it is routine practice to successfully implant the device in a child at 2 years of age or younger, whenever the skull bones are 2 mm thick (Granström et al., 2001). Because children's skulls are thinner and softer than adults', surgeons and clinicians in the United States recommend waiting for Baha implantation until the child's skull has thickened and is strong enough to hold the implant (Snik et al., 2005).

Recently, transcutaneous (across the skin) application of the Baha has been introduced for infants and young children who do not fall into the surgical category, offering a temporary solution for children awaiting surgery and/or for older children as a trial with amplification prior to surgery. This is accomplished via a Baha worn on a Baha Softband until the implant surgery is scheduled/completed. The Baha Softband is an elastic band with a Velcro fastener, with the sound processor snapped to a plastic disk sewn into the Softband. The Baha Softband was designed for infants and young children, although it can be used with children of any age, as well as with adults if required for the purpose of providing a temporary amplification experience and/or as a trial period prior to surgery. The Softband was initially designed to be used with one Baha device, although a Softband for bilateral Baha use can be obtained via special order from Cochlear Americas.

In 2005, Snik and colleagues published a consensus statement about the Baha system addressing surgical issues, the fitting range, comparison with conventional devices, bilateral applications, pediatrics, and other special issues, as well as applications for unilateral conductive hearing loss. In the consensus publication, the following were purported as evidence-based clinical practice statements to consider: (1) The Baha system outperforms conventional bone-conduction devices for both children and adults (Powell et al., 1996; Lustig et al., 2001; Tietze and Papsin, 2001; Snik et al., 2004); (2) results of transcutaneous application (via Baha Softband or Headband) are comparable with those of conventional bone-conduction devices (Hol et al., 2005); and (3) the parents should be counseled regarding surgery when the child is old enough because better gain and output (10 to 15 dB) can be obtained with percutaneous versus transcutaneous sound transmission (Håkansson et al., 1985; Tjellström et al., 2001).

Although adequate evidence is available to support the notion that the Baha implant system provides amplification superior to that of conventional bone-conduction devices, few studies have assessed audibility performance using the transcutaneous device. One notable exception is a study conducted by Hol and colleagues (2005). Participants in this study were two children with bilateral congenital aural atresia fit with the Baha Softband. Results of their study indicated that the difference in functional gain between the Baha Compact and/or Classic compared with the Oticon E 300 P were minimal; however, it was noted that functional gain at the low and middle frequencies were more favorable for the Baha than for the conventional bone-conduction device. The Hol study (2005) demonstrated that the results of Baha use with a Softband are at least comparable with if not slightly more favorable than conventional bone-conduction devices; however, their sample size was limited to two children. Furthermore, we are not aware of any studies evaluating the efficacy of the Baha coupled to the Softband in terms of audibility of the speech spectrum.

Although a Baha Headband is also available as an alternative, it consists of a metal spring band with the sound processor attached with a plastic snap. However, it has not been well accepted by the pediatric population (Snik et al., 2005). In our experience, the Baha Softband has proven to be the most comfortable and easy-to-wear alternative for infants and toddlers as well as for older children. The Baha coupled to the Softband can be fit as soon as the hearing loss has been diagnosed, reducing the auditory deprivation experienced by the child. We use this treatment alternative on a routine basis until the child is old enough and has been scheduled for surgery and/or until the benefit to the older child has been verified and validated (thus qualifying for surgical implantation).

The Joint Committee on Infant Hearing (2000) published a position statement outlining principles and guidelines for early hearing detection and intervention for children with hearing loss. Recommendations for appropriate hearing assessment techniques for infants and young children included frequency-specific auditory brainstem-evoked response (ABR), visual-reinforcement audiometry (VRA), and conditioned-play audiometry (CPA) as appropriate for the developmental level of the child (e.g., Down syndrome). These guidelines recommended a cross-check approach in which a battery of tests are used in diagnosis of the type, degree, and configuration of hearing loss. The guidelines recommended that all children receive a hearing screening before 1 month, diagnosis (if a hearing loss is present) before 3 months, and appropriate intervention before 6 months (JCIH, 2000). These recommendations have become known as the 1-3-6 goals and are further delineated in the subsequent publication of JCIH 2007 guidelines.

In 2004, the American-Speech-Language Hearing Association (ASHA) published the Guidelines for Audiologic Assessment of Children From Birth to Five Years of Age, followed in 2005 by the ASHA Guidelines for Manual Pure-Tone Threshold Audiometry for children over 5 years of age throughout adulthood. Because behavioral threshold measurement in children can be confounded by a number of developmental and maturational variables, the use of an operant conditioned response technique for threshold measurement is recommended as a standard of care. Research has demonstrated that VRA can be used to elicit consistent and reliable thresholds in children as young as 5 to 6 months of age (Moore et al., 1977; Wilson, 1978; Thompson et al., 1979; Thompson and Wilson, 1984; Primus and Thompson, 1985; Widen, 1993; Widen et al., 2000). The guidelines state that the VRA behavioral paradigm is the test of choice for assessment of hearing sensitivity for children who are chronologically/developmentally 5 through 24 months of age (adjusted for prematurity). However, for children aged 25 to 60 months (developmentally/chronologically, adjusted for prematurity), there is such a wide variation of abilities that the choice of the assessment tool may be VRA, CPA, or conventional audiometry. In a recent article, Peck (2007) described concepts and principles of behavioral measurement paradigms (i.e., VRA and CPA) that are critical to the assessment and management of young children. For a thorough review of the principles involved in behavioral threshold assessment using these approaches, the reader is referred to the following publications (ASHA, 2004, 2005; Peck, 2007).

In 2003, the American Academy of Audiology (AAA) published the Pediatric Amplification Protocol. It was organized along a traditional thematic format including guidelines regarding personnel qualifications, amplification candidacy, preselection issues and procedures, circuitry-signal processing, hearing instrument selection/fitting considerations, verification of audibility, hearing instrument orientation and training, validation of amplification benefit, and follow-up and referral. The AAA guidelines are very specific regarding hearing assessment to determine amplification candidacy and are consistent with the JCIH (2000, 2007) position statements.

Bone-conduction amplification versus air-conduction amplification was addressed as a preselection issue. Bone-conduction amplification was recommended for consideration for children with malformation of the outer ear or recurrent middle ear drainage. Unfortunately, the AAA guidelines do not address use of the Baha with a Softband or Headband for children with a permanent bilateral conductive hearing loss. The guidelines were somewhat lacking in addressing appropriate hearing-instrument selection and fitting considerations, verification of audibility, hearing-instrument orientation and training, and validation of benefit procedures for Baha and/or other bone conduction devices. Aided soundfield thresholds were addressed as a “verification” procedure in this document, which stated that aided soundfield thresholds may be useful in verification of audibility of the speech spectrum. This measure is one of the few appropriate to the large majority of clinicians fitting Baha and/or other bone-conduction devices because traditional real-ear measures with bone-conduction devices are not a viable alternative. Therefore, the purpose of this study was (1) to compare unaided and aided thresholds (i.e., to derive functional gain values) at 500, 1000, 2000, and 4000 Hz for infants and children with bilateral conductive hearing loss; and (2) to verify audibility of the speech spectrum (meeting a target aided threshold ≤20 dB HL at 500, 1000, and 2000 Hz and ≤30 dB HL at 4000 Hz). Together, the JCIH (2000, 2007) position papers and the AAA (2003) and ASHA (2004, 2005) guidelines provide guidance regarding behavioral assessment methods appropriate for infants and young children and are accepted as the standard of care for pediatric diagnostic hearing assessment.

Method

Following approval by the University of Arkansas for Medical Sciences institutional review board (IRB Protocol # 87557), a retrospective chart review of 70 infants and children fit with the Baha device through the Department of Audiology and Speech Pathology at Arkansas Children's Hospital between 2002 and 2007 was conducted. Forty-five children were excluded from this study (e.g., the child was less than 6 months of age, the etiology of the child's hearing loss was not documented, unaided and aided soundfield thresholds at four octave frequencies were not available).

Participants

Twenty-five participants met the following inclusion criteria: (1) 6 months to 18 years of age, (2) documented etiology, (3) congenital bilateral conductive hearing loss, (4) fit unilaterally with a Baha Compact via the Softband (not fit bilaterally because the Softband is designed to support one Baha), (5) unaided and aided soundfield thresholds available for four frequencies from 500 to 4000 Hz, (6) consistent full-time Baha use, and (7) followed at Arkansas Children's Hospital for 6 months or longer. Participants ranged in age from 6 months to 17.5 years; nine were boys and 16 were girls (mean age, 5.5 ± 4.5 years). Four participants were African American, one was Asian, 18 were white, and two were Hispanic. Nine participants were tested using VRA techniques (eight confirmed by frequency-specific ABR threshold estimates), 11 were evaluated using CPA (three confirmed by ABR), and five via conventional threshold measurement methods. Table 1 lists the number of participants by etiology, gender, and ethnicity. Table 2 shows the method of threshold assessment, unaided and aided thresholds for each participant, and age and etiology of hearing loss. The three-frequency pure tone average (500, 1000, and 2000 Hz) for unaided and aided thresholds is also shown in Table 2.

Table 1

Number (N = 25) of Participants by Etiology, Gender, and Ethnicity

Etiology	Gender	Ethnicity
Etiology	Gender	African American	Asian	White	Hispanic
Atresia	Female	0	0	1	0
	Male	0	0	3	0
Bony plate atresia	Female	0	0	0	0
	Male	0	0	2	0
Chromosome 18 deletion	Female	0	0	1	0
	Male	0	0	0	0
Down syndrome	Female	1	0	1	0
	Male	0	0	0	0
Goldenhar syndrome	Female	1	0	1	0
	Male	0	0	0	0
Malformed ossicles	Female	0	0	1	0
	Male	0	0	1	0
Pierre Robin syndrome	Female	0	0	1	0
	Male	0	0	0	0
Stenotic ear canal	Female	1	0	0	0
	Male	0	0	0	0
Treacher Collins syndrome	Female	0	1	3	2
	Male	1	0	1	0
Trisomy 4	Female	0	0	0	0
	Male	0	0	1	0
Velocardiofacial syndrome	Female	0	0	1	0
	Male	0	0	0	0

Table 2

Unaided and Aided Soundfield Thresholds by Participant, Age, Etiology, and Test Method^*

Participant	Age	Etiology	Test Method	Unaided Soundfield				Aided Soundfield
Participant	Age	Etiology	Test Method	500 Hz	1000 Hz	2000 Hz	4000 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz
WP	1.92	Atresia	VRA/ABR	70	70	65	60	20	20	15	20
ER	0.67	Atresia	VRA/ABR	45	60	60	55	20	20	20	25
JG	1.73	Bony plate atresia	VRA/ABR	65	60	60	65	25	20	15	15
ED	5.92	Chromosome 18 del	VRA/ABR	70	80	80	75	20	20	20	20
HG	1.01	Pierre Robin	VRA/ABR	70	70	70	60	20	15	15	15
CG	1.67	Treacher Collins	VRA/ABR	60	60	60	50	25	20	25	20
EH	2.56	Treacher Collins	VRA/ABR	50	50	45	55	20	15	20	20
SW	1.50	Treacher Collins	VRA/ABR	70	65	55	50	25	25	25	25
LL	4.70	Trisomy 4	VRA/ABR	65	70	70	55	15	20	20	15
JC	1.05	Stenotic ear canal	VRA	60	70	80	80	20	20	20	15
CC	3.16	Bony plate atresia	CPA/ABR	60	60	50	60	20	15	10	15
AH	5.22	Goldenhar syndrome	CPA/ABR	55	55	60	50	20	20	20	25
HD	3.54	Atresia	CPA	65	65	60	55	15	20	15	20
MG	3.94	Atresia	CPA	75	60	45	45	20	15	15	20
RC	17.46	Down syndrome	CPA	65	45	35	60	15	25	25	30
OP	8.77	Down syndrome	CPA	45	40	35	25	25	20	25	20
AP	3.84	Malformed ossicles	CPA	70	75	65	60	20	25	20	30
JP	5.97	Malformed ossicles	CPA	65	80	65	85	20	20	15	25
BH	6.81	TM perforations	CPA	40	40	35	25	20	20	15	20
EU	2.52	Treacher Collins	CPA	50	40	30	45	20	20	15	25
MD	11.38	Goldenhar syndrome	Conventional	60	55	50	40	25	20	15	15
JD	12.72	Treacher Collins	Conventional	65	50	50	45	15	10	15	20
CH	14.01	Treacher Collins	Conventional	70	70	70	60	20	15	15	15
SR	9.75	Treacher Collins	Conventional	60	60	55	50	20	15	10	20
VU	6.98	Treacher Collins	Conventional	60	55	60	60	20	15	20	15
Mean	5.55			61.2	60.2	56.4	54.8	20.2	18.8	17.8	20.2
PTA				59.27				18.53

VRA = visual reinforcement audiometry; ABR = auditory brainstem evoked response; CPA = conditioned play audiometry; PTA = pure tone average (500, 1000, and 2000 Hz).

Procedure

Data available in the medical record were collected in one of three double-walled sound booths at Arkansas Children's Hospital, all of which were equipped with a Grason Stadler G-61 audiometer calibrated in decibels hearing loss to meet the American National Standards Institute (ANSI) specifications (ANSI, 1996; Frank, 1997). Although otoscopy and tympanometry were conducted, there were many missing data relative to the child's etiology (e.g., atresia, bony canal atresia); therefore, otoscopy and tympanometry results are considered irrelevant and are not reported here. All hearing thresholds were obtained following the ASHA Guidelines for Audiologic Assessment for Children From Birth to Five Years of Age (2004) if tested via VRA or CPA. For VRA, a head turn to a warbled pure tone or narrow-band noise stimulus was considered a response. Two or more thresholds were obtained at each frequency. For CPA procedures, the “play” response was dropping a small plastic toy (e.g., turtles, cars, alligators) into a small pail. For children tested via conventional behavioral methods, the ASHA Guidelines for Manual Pure-Tone Threshold Audiometry (2005) was used. Children were asked to raise a hand when they heard a tone. For each procedure, thresholds were recorded at the lowest intensity at which two or more responses at each frequency was obtained. Medical records of participants with bilateral conductive hearing loss who were fit unilaterally with the Baha Compact using the Softband were reviewed. From the audiograms available in the medical records, ear- and frequency-specific thresholds obtained via supra-aural headphones at 500, 1000, 2000, and 4000 Hz were recorded on datasheets and transferred to an Excel spreadsheet. The method of behavioral threshold assessment was recorded and included in the database (see Table 2 for individual results). Figure 1 shows an example audiogram depicting a bilateral conductive hearing loss obtained via VRA. Figure 2a shows a 10-month-old boy with a diagnosis of bilateral microtia and atresia, as well as cleft palate. He is shown wearing a Baha device with a Softband. Unaided soundfield (U) and Baha (B)-aided thresholds in decibels hearing loss via VRA for the patient are presented in Figure 2b. Audiometric data for frequency-specific unaided and aided soundfield thresholds obtained with the speaker positioned at a 90° azimuth to the target ear were likewise recorded and transferred to the Excel spreadsheet at corresponding frequencies. For each participant, unaided and aided soundfield thresholds were obtained with methods similar to those used for ear-specific data. Although diagnostic and therapeutic threshold measurement is an ongoing process with very young children, only data from children for whom a complete dataset of threshold information was available were included in this study.

Figure 1

An audiogram depicting a typical bilateral conductive hearing loss due to congenital atresia is shown. Right and left ear air- and bone-conduction thresholds are indicated by the symbols indicated in the legend.

Figure 2

a: A 6-month-old boy with bilateral congenital microtia and bony plate atresia using a Baha fit via the Softband. b: Unaided soundfield (U) and aided Baha (B) hearing thresholds (HL) in decibels (dB) hearing level (HL) for a patient with bilateral congenital atresia.

Results

Data were subjected to descriptive statistical procedures. Means and standard deviations were computed for ear-specific air-conduction thresholds, unmasked bone-conduction thresholds, and for unaided and aided soundfield thresholds. Group data are presented in Table 3. Mean thresholds, standard deviations, and 95% confidence intervals (CI) for right-ear air conduction, left-ear air conduction, and unmasked bone conduction thresholds in decibels hearing loss are displayed. The mean conductive loss at 500, 1000, 2000, and 4000 Hz, is 54.6 ± 4.9 dB, 47.4 ± 5.6 dB, 42.3 ± 4.7 dB, and 41.3 ± 5.4 dB, respectively (calculated by subtracting the unmasked bone-conduction threshold at each frequency from the averaged air-conduction thresholds for right and left ears).

Table 3

Mean Air-Conduction and Unmasked Bone-Conduction Thresholds in dB HL, 95% CIs, and SDs for Thresholds Obtained Under Supra-Aural Headphones at 500, 1000, 2000, and 4000 Hz^*

Condition	500 Hz	1000 Hz	2000 Hz	4000 Hz
Right ear AC
M (SD)	65.8 (8.9)	59.6 (12.8)	55.2 (9.8)	53.8 (13.1)
95% CI	62.3, 69.3	54.6, 64.6	51.3, 59.0	48.6, 53.6
Left ear AC
M (SD)	64.6 (9.5)	60.4 (11.9)	56.6 (10.4)	54.4 (12.0)
95% CI	60.9, 68.3	55.7, 65.1	52.5, 60.7	49.7, 59.11
Unmasked BC
M (SD)	10.6 (4.9)	12.6 (5.6)	13.6 (4.7)	12.6 (5.4)
95% CI	8.7, 12.5	10.4, 14.8	11.8, 15.4	10.5, 14.7
Mean conductive loss
M (SD)	54.6 (4.9)	47.4 (5.6)	42.3 (4.7)	41.3 (5.4)
95% CI	8.7, 12.5	10.4, 14.8	11.8, 15.4	10.5, 14.7

dB = decibel; HL = hearing level; AC = air conduction; BC = bone conduction; M = mean; SD = standard deviation; CI = confidence interval.

Table 4 shows the mean unaided and aided thresholds obtained in the soundfield with the speaker positioned at a 0° azimuth to the target Baha and standard deviations for each measurement as well as the mean functional gain (computed by subtracting the mean aided threshold from the mean unaided threshold). One-tailed, paired t tests were used to determine whether there was a significant difference between the aided and unaided thresholds. Results indicate significantly better aided thresholds versus unaided thresholds at each frequency (p < .0001).

Table 4

Mean and Standard Deviations of Behavioral Hearing Thresholds in dB HL Obtained in the Soundfield at 500, 1000, 2000, and 4000 Hz for Unaided and Aided Conditions (90° Azimuth Relative to the Target Ear) Using a Baha Compact Fitted to the Softband. Aided Thresholds Were Subtracted From the Unaided Thresholds to Compute Mean Functional Gain Scores^*

Condition	500 Hz	1000 Hz	2000 Hz	4000 Hz
Unaided SF
M (SD)	61.2 (9.2)	60.2 (11.7)	56.4 (13.6)	54.8 (13.9)
95% CI	57.6, 64.8	55.6, 64.8	51.8,61.7	49.4, 60.2
Aided SF
M (SD)	20.2 (3.1)	18.8 (3.6)	17.8 (4.8)	20.2 (4.7)
95% CI	19.0, 21.4	17.4, 20.2	16.1, 19.5	18.4, 22.0
Functional gain
M (SD)	41.0 (6.1)	41.4(8.1)	38.6 (9.2)	34.6 (9.2)
95% CI	38.6, 43.4	38.2, 44.6	35.0, 42.2	31.0, 38.2
Paired t test statistic for unaided-aided values	20.29	17.45	13.47	11.7
p value	<.001	<.001	.001	.001

dB = decibel; HL = hearing level; SF = soundfield; M = mean; SD = standard deviation; CI = confidence interval.

Although group mean thresholds were within the target range to ensure audibility of the speech spectrum, these values do not provide information about the individual children. Target aided thresholds were ≤20 dB HL at 500, 1000, and 2000 Hz and ≤30 dB at 4000 Hz. Aided soundfield thresholds for each child were compared with the target thresholds and evaluated using a percentage agreement approach, with 80% chosen a priori as the criterion test value. When the participant's individual threshold met target, it was defined as success. The 80% criterion test value was chosen as a reasonable compromise between a chance level of 50% and absolute agreement of 100% and has been used similarly in previous studies (Smith-Olinde et al., 2006). Observed probabilities for all frequencies with p values and statistical power are presented in Table 5. Results indicate that the percentages of agreement for each frequency (i.e., 80%, 92%, 84%, and 92% at 500, 1000, 2000, and 4000 Hz, respectively) are not statistically different from the a priori criterion of 80% and that the statistical power in each case is quite low. Perhaps more clinically relevant, however, is the group percentage of aided thresholds at each frequency that met or exceeded the criterion value of .80. If we change the definition of success to include aided thresholds that are no more than 5 dB poorer than the target values, the percentage of successes at each frequency rises to 100%. The rationale for use of this 5-dB magnitude is based on the conservative estimate of test-retest limits in clinical testing (Carhart and Jerger, 1959) for conventional audiometry.

Table 5

Target Aided Thresholds in dB HL, the Number and Percentage of Participants Meeting Threshold Targets (N = 25), 95% CIs, Level of Significance, and Statistical Power at Each of Four Frequencies^*

	.5 kHz	1 kHz	2 kHz	4 kHz
Target aided thresholds	≤20 dB HL	≤20 dB HL	≤20 dB HL	≤30 dB HL
Number of thresholds meeting target	20	23	21	23
Percentage meeting target	80	92	84	92
95% CI	76.08, 83.92	73.08, 80.92	82.92, 75.08	73.08, 80.92
p value	.617	.098	.421	.098
Statistical power	.050	.415	.105	.415

dB = decibel; HL = hearing level; CI = confidence interval.

Discussion

Congenital conductive hearing loss may be readily apparent when craniofacial deformities occur at birth with and/or without an associated syndrome or association. Timely identification and management of this type of hearing loss is desirable, preferably before the age of 6 months (Yoshinaga-Itano, 1999; JCIH, 2000, 2007). Although diagnosis of the hearing loss may occur expeditiously, clinicians are challenged to provide amplification technology within the desirable time frame. Because metal headbands used with conventional bone-conduction devices are uncomfortable and impractical for use with infants, the Baha Softband has been suggested as a viable alternative (Hol et al., 2005). However, data documenting efficacy of intervention have been limited. The present study provides data for 25 infants and children documenting the efficacy of use of the Baha device coupled to the Softband as an initial intervention and/or as a prerequisite to or in lieu of surgical intervention.

Although a number of studies have looked at the Baha implant system compared with conventional bone-conduction devices for both children and adults (Powell et al., 1996; Tietze and Papsin, 2001), only one study has reported data for two children with bilateral congenital aural atresia fit with the Baha Softband. This study builds upon the results of Powell et al. (1996), Tietze and Papsin (2001), and Hol et al. (2005), demonstrating that 100% of the aided Baha thresholds were within +5 dB of the target thresholds at all frequencies, thus ensuring audibility of the speech spectrum. Furthermore, the current data confirm that functional gain at 500 Hz is significantly better than at 4000 Hz. In essence, ear-specific thresholds showed hearing thresholds significantly worse at 500 than at 4000 Hz (reverse slope configuration of hearing loss), functional gain values indicate a “flat” aided threshold configuration. This study provides data verifying that access to auditory information critical for the development of speech and language skills. For older children who have developed permanent conductive hearing loss and/or those children who are late identified, the Baha Softband represents a means of temporarily fitting the device, allowing for verification of audibility and validation of benefit over a period of time prior to a decision regarding implantation.

Because the Baha Softband is an elastic band with a plastic-snap connector disk sewn into an elastic band with a Velcro fastening, it is a comfortable way to use the Baha without or prior to surgery. It can be adjusted to fit the size of each child's head, which makes it useful for newborns and preschoolers as well as older children. The Softband enables audiologists to fit patients younger than 6 months, meeting the 1-3-6 goals for early intervention established by the Centers for Disease Control and Prevention and endorsed by the JCIH (2000, 2007).

We have demonstrated that the ability to meet target aided thresholds, thereby ensuring audibility of the speech spectrum, is relatively easy to achieve. An aggressive approach to amplification and ongoing verification of auditory access to speech sounds coupled with other early intervention and/or speech language services will facilitate developmental progress. In addition, we would be remiss if we did not also reinforce the fact that the Baha system coupled via a Softband (as well as with implantation) also can be used with an frequency modulation (FM) system in the car, classroom, and other difficult-to-hear situations, thereby providing children with the same access to the auditory signal that other hearing aid and cochlear implant users experience. The Baha FM receiver plugs directly into the Baha signal processor. Together, these findings support the use of the Baha system coupled to the Softband as the most viable first option as an amplification intervention technique for this population.

Limitations

It is important to recognize the impact that behavioral hearing tests have on the results. Although young children are often difficult to evaluate using behavioral measures, reliable results may be obtained when clinicians with significant experience in the pediatric population are the examiners. Whereas test-retest reliability for conventional audiometry using supra-aural or insert earphones is ±5 dB, the test-retest reliability for the pediatric population for VRA and CPA is typically ±10 dB (Moore et al., 1977; Wilson, 1978, 1984; Thompson et al., 1979; Primus and Thompson, 1985; Thompson and Widen, 1993; Widen et al., 2000). Caution must always be used to reduce extrinsic factors that may contribute to variability, such as test directions, procedures, and methodology, hence the need for professional guidelines (ASHA, 2005). The existing guidelines do not provide specific information about acceptable test-retest variability for each behavioral measurement paradigm based on evidence available in the literature, nor do they address the variability of pediatric thresholds across a wide age range (i.e., infancy through adolescence). Therefore, the variability of threshold measurement for this study may be influenced by the inclusion of infants and young children.

The use of soundfield measurement as a verification tool for air-conduction amplification has been criticized in the literature due to the poor test-retest reliability, poor frequency resolution, and the prolonged cooperation required from a child. However, with the Baha system, verification choices are limited. Probe tube microphone measurements are inappropriate, and soundfield verification of audibility is the best option available to date.

Participants in this study were fit unilaterally with the Baha worn on a Softband. From a cohort of about 70 Baha users, 45 children did not meet the inclusion criteria. All of the children included in this study had documented etiologies with associated cleft palate and/or craniofacial anomalies including atresia. Data from children wearing bilateral Bahas with a Softband or either unilateral or bilateral implanted Bahas may differ. Caution must be used in generalizing the results of this study to populations of children who do not have similar characteristics.

Conclusions

The results of this study are consistent with the conclusions of Snik and colleagues (2005), supporting the use of the Baha system as a viable treatment for permanent congenital and acquired conductive hearing loss for infants and children. Participants in this study showed an average of 40 dB of functional gain when wearing the Baha Compact coupled to a Baha Softband. Aided soundfield thresholds meet target audibility criteria for the children in this study at each of the four octave frequencies (500, 1000, 2000, and 4000 Hz) when success is defined as within ±5 dB of the target. Despite the limitations of this study, these results undeniably demonstrate the benefit of bone-conduction amplification via the Baha device coupled to the Softband. Results of this study provide timely data necessary to demonstrate support for third-party reimbursement.

Footnotes

Acknowledgment

The authors would like to thank George Cire, Mark Flynn, and Tom Guyette for their review of previous drafts of this manuscript and for their thoughtful comments and suggestions for revision.

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