Discussion
Malformations of the external and middle ear can be associated with sensorineural
or conductive hearing loss. Conductive hearing loss is common when there is atresia
external auditory canal (EAC) stenosis, or malformation of the ossicular chain. Many
authors have reported favorable outcomes of BAHA surgery and ear reconstruction.
BAHA surgery is a relatively simple procedure that was approved by the FDA in 1996
for adults and in 1999 for children above 5 years of age[2]
[10] (if a 3-mm fixer is installed, a bone density of at least 2.5 mm is necessary; this
occurs at approximately 5 to 7 years of age[3]) and can be completed in a single session or over 2 sessions. Before the age of
5 years, patients can be rehabilitated with a bone vibrator attached to an elastic
band (soft band). Verhagen et al.[4] evaluated 12 children with congenital atresia of the EAC. The children had an average
age of 2 years and 3 months (1 month to 5.5 years), with hearing thresholds below
60 dB that reached approximately 27 ± 6 dB with the use of the bone vibrator, suggesting
that this amplified sound as well as the BAHA. Hol et al.[5] also supported the use of the band with bone vibrator in small children after following
2 children (1 of whom had a BAHA bilateral soft band, which provides a binaural summation of approximately 3 to 5 dB).
Some authors recommend BAHA before 5 years of age, as this period is crucial for speech
development. Davids et al.[6] performed BAHA surgeries between 1996 and 2006 and divided the patients into 2 groups:
below 5 years of age (20 patients) and above 5 years of age (20 patients). In 38 patients,
the surgery was performed in 2 stages. The main difference between the age groups
was a longer gap between the first and second stages of the procedure in the below-5-year-olds
to ensure osteointegration. Complications included a higher incidence of skin growth
or infection among the younger patients (3 in the younger group and 0 in the older
group), while the incidence of traumatic loss was similar (2 in the younger group
and 4 in the older group). There were no osteointegration flaws in any of the patients
below 5 years of age. Mazita et al.[7] performed BAHA surgery in a single session only in patients older than 12 years.
Of the 16 patients in their study who underwent the procedure (11 of them in 2 stages),
there was an average airway conduction threshold improvement from 64.9 dB preoperatively
to 29.7 dB postoperatively, with an average functional gain of 35.2 dB. The authors
noted that percutaneous BAHA transmission is more efficient by 10 to 15 dB than transcutaneous
transmission, and they also advocate the use of the elastic band in children younger
than 3 months old[7].
Rotenberg et al.[8] describe the experience of establishing a BAHA program, including treatment algorithms,
protocols, methodology, complications, and patient satisfaction. In their program,
the initial assessment occurs between birth and 4 years of age, when the parents are
contacted and informed of treatment options. When there is atresia or malformation
of the middle ear, hearing is also evaluated. Once the patient is 5 years old, the
parents are called for a discussion about the treatment and receive information about
postoperative care and follow-up. The authors quoted their data from a retrospective
analysis of 11 cases. The complications included only 1 case with excessive growth
of soft tissues, which can be avoided during the initial skin preparation with circumferential
debridement of the tissues and application of a thin, hairless skin graft. Bone growth
around the fixer can be avoided by removing the surrounding periosteum. This is highly
satisfying to the patients and their parents, and the major complaints involve esthetics
and the necessary care for the device required during physical activities.
The conventional procedure usually requires 2 surgical sessions, and the literature
suggests a gap of 3 to 6 months between the procedures. During the first session,
a titanium pin is fixed in the bone. The second session involves the removal of fat,
excess subcutaneous tissue, and hair follicles, along with a skin puncture to expose
the fixer. The BAHA is finally adapted 6 to 8 weeks after the second procedure. Ali et al.[9] performed a study with 30 children who underwent surgery between 1997 and 2005.
Surgery conducted in a single session was associated with few complications (2 infections
of the surgical site, 1 skin hypertrophy, 1 chronic infection, and 2 losses of implant
after local trauma) and had the advantage of avoiding a second exposure to anesthesia.
Bento RF conducted unilateral BAHA implants in 13 patients between 2000 and 2009. The causes
of hearing loss were Treacher Collins syndrome[3], EAC atresia (9 total, 6 of which were bilateral), and mastoid cavity[1]. The age of the patients ranged from 3 to 34 years (average 14.3). In preoperative
audiometry, 10 patients had a gap of 30 to 40 dB and 2 had mixed loss with a gap of
30 dB (audiometry was not possible for 1 patient). Seven patients exhibited closure
of the air-bone gap (4 with bilateral EAC atresia, 2 with Treacher Collins syndrome,
and 1 with mastoid cavity), there were 2 whose sensorineural loss persisted (they
had mixed loss before the surgery), and 6 patients had a persistent 10 dB gap postoperatively
(3 EAC atresia, 2 bilateral EAC atresia, and 1 Treacher Collins syndrome). There were
no significant differences between the audiometric results according to the cause
of the hearing loss, and 1 patient who underwent a previous mastoidectomy surgery
with a preoperative gap of 40 dB had an excellent outcome (closure of the air-bone
gap). The surgery was performed in a single procedure in all patients, except in 1
with Treacher Collins Syndrome, and there were no postoperative complications.
The incidence of aural atresia is estimated to be 1 per 10,000 births; in 25% of cases,
the atresia is bilateral[10]. Fuchsmann et al.[10] evaluated BAHA results in 16 patients with an average postoperative threshold of
25.4 ± 5.7 dB (average gain of 33 ± 7 dB). The average postoperative air-bone gap
was 10.5 ± 5.9 dB, and there was closure of the gap in 10 patients. The free-field
speech recognition threshold improved from 63 dB to 30 dB. For most surgeons, a pure-tone
air threshold of 30 dB or less represents a good result, and 85% of the patients in
this study exhibited such thresholds.
Ricci et al.[2] evaluated the audiometric results in 47 patients who underwent BAHA. In this group,
31 had bilateral congenital atresia, 9 had chronic otitis media or history of ear
surgery, and 7 had osteosclerosis. The average preoperative air-bone gap was 33.2 ± 16.5
dB. There was a closing of the gap in 40 patients, and 14 had overclosure, when the
BAHA threshold overcomes the preoperative bone conduction threshold. Carlsson and Hakansson
[11] related this phenomenon and stated that when the BAHA reaches its maximum potential,
the air-bone gap can virtually close, with an additional maximum sensory compensation
of 5 to 10 dB at frequencies between 700 and 3000 Hz. Speech perception also improved
in approximately 31 patients by 64 ± 31% at 60 dB HL. Of the 9 patients with chronic
otitis media, 7 exhibited improvement in the infection. MacNamara and Mylanus reported
similar results (quoted in Ricci et al.[2]). Forty-five patients in their study answered a questionnaire and reported an improvement
in quality of life after BAHA surgery. The authors reported 3 cases with complications,
2 with skin growth around the implant, and 1 with extrusion due to osteointegration
failure. McDermott et al.[11] in a retrospective study of 182 children who underwent BAHA implantation surgery,
had success in 97% of the patients who used the implant daily. Kunst et al.[13]
[14] implanted BAHAs in 20 patients with unilateral conductive hearing loss. The bone-conduction
thresholds were normal in both ears, with a gap in the affected ear of 50 dB. All
the patients presented speech recognition and free-field thresholds better than 25 dB
with BAHA use. Patients with acquired conductive loss[2] showed the greatest improvements in sound localization after BAHA. One unexpected
finding was a good result in the ear without the BAHA with improvements in speech
comprehension, particularly in cases of congenital hearing loss. The authors stated
that further studies are needed to explain this finding. Consistent use of the device
is highly predictive of the benefit to the patient, and even in cases for which the
exams did not show significant gain, patients who used the device were satisfied[10]
[14]. The authors also evaluated subjective improvement through questionnaires and concluded
that most patients seemed to benefit from BAHA use[12].
In the largest series, the best hearing results with BAHA were achieved when the cochlear
reserve (bone threshold) was better than 45 dB. Lusting et al.[1] confirmed this finding when they evaluated the first 40 patients rehabilitated with
BAHA in the United States. Twenty-one patients had hearing loss due to chronic otitis
media, 9 due to EAC atresia/stenosis, 5 due to osteosclerosis or congenital hearing
loss, 3 after skull base surgery, 1 for keratosis obliterans, and 1 for conductive
hearing loss of unknown cause. The preoperative gap was 38 ± 16 dB. Eighty percent
of patients obtained a 10 dB gap reduction, 60% achieved a 5 dB reduction, and 30%
presented overclosure. The best audiometric results were achieved in patients with
osteosclerosis or congenital hearing loss who presented a 42 dB increase with BAHA.
The chronic otitis media patients had an average of 33 dB gain, and the EAC stenosis/atresia
patients had an average of 22 dB gain. Patients with hearing loss due to surgery at
the base of the skull had the worst outcomes. Complications included a flaw in osteointegration
in 1 patient and local skin reaction in 3 patients. One patient was not satisfied
with the sound quality achieved by the anchored prosthesis.
Another modality for treating hearing loss in cases of atresia and ear malformation
is reconstructive surgery, particularly canaloplasty, tympanoplasty, and stapes and
ossiculoplasty, whether including or not including associated aesthetic reconstruction
of the hearing pavilion. Evans and Kazahaya
[15] compared the results of reconstructive surgery in 29 patients versus BAHA in 6 patients
in a pediatric population. The average hearing gain in dB was 17.7 after the reconstructive
surgery and 31.8 dB after BAHA. In this study, 93% of patients required sound amplification
postoperatively, even after reconstructive surgery, and there were 18 cases of late
complications, most commonly recurrent EAC stenosis (8 patients) and recurrent otitis
externa (7 patients). In the BAHA group, there was only 1 complication (hypertrophic
scar). These findings encompass the main reasons why reconstructive surgery is currently
discouraged in most centers.
In 1993, Granstrom et al.[16] published a study of 111 patients, 45 with bilateral modification (156 ears total)
who underwent a total of 134 reconstructive surgeries. The most common causes of malformation
were Treacher Collins syndrome (21 patients) and hemifacial microsomia (18 patients).
In 73 ears, aesthetic surgery was performed with placement of an auricular prosthesis.
Severity of hearing loss was found to be proportional to the severity of the malformation,
while the hearing gain with the reconstructive surgery was lower for the more severe
malformations. The hearing improvements for 44 ears after more than 2 years of follow-up
were poor (0 to 10 dB) in 24 patients, moderate (10 to 30 dB) in 19, and good (above
30 dB) in only 5 patients. Twenty-four ears required reoperation, mainly due to restenosis[10] and continuous otorrhea[3]. BAHA surgery was performed in 39 patients. In all cases, both the patients and
their surgeons were satisfied with the results. The results for the aesthetic auricular
prostheses were also good, as 72 of the 73 patients were satisfied with the surgery.
In this study, the authors agreed with the general consensus in the literature that
ear reconstruction surgery is one of the most difficult of the otological procedures,
and disappointing results for both aesthetics and hearing (in this study, only 34%
of patients reached the social level of hearing), along with the increase in experimental
BAHA use, have led to a more conservative approach toward reconstructive surgery.
Chang et al. (2006)[17] also correlated severe microtia and surgical revisions with lower audiometric gains
after reconstructive surgery (15.3 dB in revision surgeries versus 20 dB in primary
surgery, after 3 years) concluding that in these cases, BAHA must be offered as an
alternative, as it can provide more secure and stable results. Mazita et al.[7] recommend canaloplasty in patients with normal pneumatization of the middle ear
and mastoid in whom the facial nerve, the ossicular chain, and middle and inner ear
are normal or minimally affected.
The placement of a prosthetic hearing pavilion with aesthetic finality is another
alternative to reconstructive surgery. In these cases, the functional portion can
be complemented with BAHA placement. In the study mentioned above, Ganstrom et al.[16] compared the results of reconstructive surgery with those of BAHA and the pavilion
prosthesis coupled to the bone in 111 patients and 134 reconstructive surgeries, including
73 surgeries for placement of the pavilion prosthesis and 39 BAHA insertions. All
of the patients in the BAHA group considered the BAHA superior to conventional amplification
devices, and 72 of 73 pavilion prosthesis patients were satisfied with their prosthesis,
while only 8 of the 37 reconstructive surgery patients were satisfied, and only 34%
achieved a social level of hearing. The authors suggested that reconstructive surgery
should be contraindicated for unilateral congenital atresia and took the same conservative
approach to bilateral atresia in light of their disappointing results and the increasing
experience with BAHA. In 2001, the same authors published data from the 100 patients
who first underwent the surgery, 76 of whom had BAHAs or aesthetic anchored prostheses
implanted[3]. Complications included adverse skin reactions in 9.1% and implant failure in 5.8%.
Revision surgery was necessary in 22% because their temporal bones were still growing.
Most of the revisions occurred in patients between 5 and 11 years of age, a period
during which the bone grows considerably. The authors did not indicate aesthetic surgery
for patients younger than 5 years of age.
Somers et al.[18] compared the results of reconstructive plastic surgery with attachment of a prosthesis
anchored to the bone. They studied 62 patients, among whom 35 had prosthesis placement
and 27 had reconstruction. The reasons for surgery were anotia/microtia (26), trauma
(6), and oncological (3). The rate of satisfaction among the prosthesis patients was
high, with 34 patients who reported using the prosthesis every day. The complications
included skin growth in 1 patient, skin reaction in 9 patients, and excessive subcutaneous
tissue required reduction in 2 patients. The disadvantages of the prosthesis included
the daily care requirements, occasional loss, and color change over time. Among the
reconstructive surgeries, 21 were performed using the Nagata technique (preferred
by the authors, conducted in 2 surgery sessions). The authors indicated this procedure
for patients up to 6 years old, which is when the ear reaches about 85% of its adult
size. The results were considered very good for 9 patients, good for 12, acceptable
for 5, and bad for 2. The greatest failure rate occurred during the initial period.
In cases of anotia and microtia, the authors only indicated prosthesis placement when
the patient refused reconstruction, when reconstruction had already failed, when the
cause was trauma or cancer, and for patients with multiple comorbidities. The authors
indicate BAHA for patients who are undergoing reconstructive plastic surgery while
awaiting functional surgery.
The hearing gain from BAHA can change over time, as Saliba et al.[19] demonstrated. The authors evaluated the hearing of 17 patients preoperatively, on
the day of insertion, and 6 and 12 months post-insertion. They found that the gain
in speech discrimination at 1 year was better than immediately after the insertion
(21.9% versus 11.7%), suggesting a learning process over time. The greater gain occurred
in the presence of background noises. When speech intelligibility is measured binaurally
with spatial separation of the sources of speech and noise, the threshold can vary
up to 10 dB in individuals with normal hearing; in this study, the worst thresholds
occurred when speech and noise came from the same source, while the best thresholds
occurred when speech and noise sources were 90° apart. The pure-tone average after
1 year was comparable to the results immediately after the insertion.
The indications for BAHA are not limited to conductive loss. Christensen et al.[20], in a pilot study, implanted BAHAs in 23 children with deep unilateral sensorineural
hearing loss. These children usually display poor school performance in noisy environments
because of their hearing disability. The procedure was performed in 2 sessions, and
hearing gains were demonstrated by improved scores on the Hearing in Noise Test (HINT) and the Children's Home Inventory for Listening Difficulties (CHILD) questionnaire. Among the study patients, there was an improvement of 40%,
21%, and 4% in 0, 5, and 10 dB, respectively, on the HINT and improvements of 2.41
for the patients and 2.5 for the parents as shown by the CHILD questionnaire scores.
More recent studies have supported the use of BAHA for patients with unilateral sensorineural
deafness. Between 2006 and 2008, Wazen et al.[21] studied 21 patients with air-conduction thresholds worse than 90 dB or speech discrimination
lower than 15% for the most affected side and light-to-moderate contralateral deafness.
The BAHA was implanted on the side with the worst hearing. The average age of the
patients was 75 years. Hearing was measured with and without the BAHA and with 2 kinds
of processor, Intense® and Divine®. There was a statistically significant postoperative improvement in both hearing
thresholds and speech recognition scores versus pre-operation, and 91% of the patients
reported improved quality of life on the Glasgow questionnaire. A significant difference
in the HINT test scores favored the Intense® processor, which also provided a higher average functional gain (>55 dB versus ≤45
dB). The authors concluded that the BAHA is effective in the rehabilitation of patients
with unilateral sensorineural deafness. Hol et al.[22] studied 27 patients with unilateral sensorineural hearing loss (25 acquired and
2 congenital) and evaluated the gain with BAHA CROS (transcranial routing of sound).
They found poor results for sound localization, but improved scores for speech in
noise, subjective benefit, and client satisfaction among those who answered the appropriate
questionnaire.
