IMPLANTABLE HEARING AIDS: CANDIDACY CONSIDERATIONS IN PEDIATRIC CHOLESTEATOMA

Adrian L James, Sharon Cushing, Blake C Papsin

Department of Otolaryngology – Head and Neck Surgery, University of Toronto; Hospital for Sick Children, Toronto, Canada

Introduction

Tympanic membrane retraction and cholesteatoma are the commonest causes of permanent conductive hearing loss acquired by children in westernized societies. Surgery frequently fails to restore normal hearing after removal of cholesteatoma, usually because of damage to the ossicular chain. Although usually unilateral, the hearing loss may interfere with schooling and socialization. Parents are frequently concerned about this limitation in their child, however the child or adolescent only rarely seems to express any major concern. Consequently most teenagers decline the offer of rehabilitation of their unilateral conductive loss with hearing aids or an extra surgery for ossiculoplasty.

Personal experience suggests that the factors that deter these young people from seeking rehabilitation include: (1) denial that they have a problem that needs fixing; (2) desire not to look different from their peers (e.g. by wearing a hearing aid); (3) desire to avoid surgery. Implantation of an active hearing aid at the time of surgery for cholesteatoma has the potential to overcome all of these objections. This would allow these individuals to experience the benefits of binaural hearing without having an additional surgery. Totally implantable devices, or those with a small external device hidden within the hair and held in place by trans-cutaneous magnets (rather than a percutaneous fixture) would overcome the cosmetic concerns of aids worn in and around the external ear.

The differing designs of IHA devices influence potential candidacy. Conventionally most are intended to be placed with an intact ear canal wall and several require attachment to the ossicular chain: both may be absent after cholesteatoma surgery. However, although most currently available IHA are not currently licensed for use in children, and were designed for sensorineural or mixed losses rather than the purely conductive loss typical of most children with cholesteatoma, some children could benefit from these devices. The objective of this study is to determine the proportion of children that would be potential candidates for current IHA according to the configuration of devices currently available.

Method

The presenting features of cholesteatoma, surgical outcomes and hearing levels were recorded prospectively in a consecutive series of over 300 cases over a seven year period. This database was reviewed to determine the status of the canal wall and ossicular chain following completion of cholesteatoma surgery. Hearing threshold at the clinic visit closest to 12 months after the last surgery to the affected ear was recorded. Normal hearing was defined as a four tone average air conduction threshold of <30dB HL. Ears with hearing thresholds above this level were considered potential candidates for rehabilitation. Ears with <12 months follow up after their last surgery were excluded in order to exclude all cases in whom planned, staged surgery had not been completed. One case of profound congenital sensorineural hearing loss that had been identified through the department’s cochlear implant program was also excluded. 27 cases described as “precholesteatoma” were included in this series and were defined by the presence of increasing depth of retraction under the scutum, annulus or ear drum and presence of granulation tissue and or retained keratin within the retraction that was potentially cleanable without surgery.

Cholesteatoma was removed with an intact canal wall approach when practical using endoscopy, KTP laser and cartilage reconstruction as adjuncts. Second stage surgery was planned when removal of disease was piecemeal or extended posterior to the intact canal wall. Prosthetic ossiculoplasty (TORP) was offered at the second stage of canal wall up surgery in cases of absent stapes superstructure, though was often declined by the individual or parents because of concerns arising from the potentially low success rate and possible requirement for surgical revision in the future. IHA and bone anchored hearing aids were not used in this series.

Results

Of the 283 children in the database, 20 had bilateral cholesteatoma (7% of 303 cases). 26 ears were excluded from analysis (1 profound congenital SNHL; 25 cases <12 months follow up). The mean age at surgery of the 277 cases included was 11 years. Cholesteatoma most commonly arose from retraction of the pars tensa (54%) rather than the pars flaccida (24%). Other derivations of cholesteatoma were: congenital (12%), implantation (7%), ear canal (3%).

Of the 277 cases, an intact canal wall was preserved in 209 cases (75%). Of the 68 canal wall down cases, 23 (8% of all cases) had a single CWD procedure and the remainder were revision surgeries following previous ICW or CWD procedures (22 were referred after previous CWD surgery elsewhere). An ICW approach was completed in 82% of all newly diagnosed cases (209 of 252).

After ICW surgery, the ossicular chain was intact in 36 cases (17%) and the stapes superstructure was intact in 100 (48%) cases. Of those with absent stapes superstructure, 17 had a TORP and 25 an incus interposition ossiculoplasty.

A postoperative audiogram around one year after surgery was available for 218 cases. Overall, 120 (55%) ears had hearing loss (i.e. mean 4 tone average air conduction hearing thresholds >30dB HL): 91 (52%) of the ICW cases and 29 (66%) of CWD cases. Of the ICW cases with hearing loss, only 2% had an intact os-sicular chain, and 17% had an intact stapes when the malleus or incus were deficient. Hearing loss persisted after ossiculoplasty for absent stapes superstructure in 42% of TORPs and 79% of incus interpositions.

The proportion of children hypothetically eligible for different designs of IHA is shown in Table 1. The applicability of different device requirements is based on examples of currently available IHA, regardless as to whether they are designed or licensed for use in pediatric conductive hearing loss. It is assumed that an ICW is necessary for most devices, though placement of at least one type of device has been reported with open mastoid cavities.

Table 1. Table to show the proportion of ears in which different designs of implantable hearing aid may be appropriate, according to ossicular status.

image

image

Fig .1. Kaplan Meier survival curve for recurrence of cholesteatoma after intact canal wall surgery. Time in months after first stage of surgery.

Overall 25% of all cases were found to have recidivistic cholesteatoma (i.e. recurrent and/or residual disease) with follow up of 12 to 80 months. 107 (51%) ICW cases had a second stage procedure because of identification of recurrent cholesteatoma at follow up or concern about a high risk of residual disease. Recidivism was present in 46% of these cases: 34% had residual disease which was typically a small pearl of cholesteatoma and 22% had recurrent disease, often from retraction around a cartilage scutumplasty. Figure 1 is a Kaplan Meier curve showing the tendency of cholesteatoma to recur at a fairly constant rate for years after surgery. Follow up is not available after age 18 years as care of all cases is transferred to other institutions.

Conclusions

Hearing loss is common after surgery for cholesteatoma in children. Loss of ossicular integrity is the principal cause and this is often not successfully rehabilitated by ossiculoplasty. The high likelihood of hearing loss and good prospect of maintaining the canal wall suggests great potential for benefit from IHA in children. Limitations for pediatric IHA candidacy include:

1.Ossicular status: Good hearing can be anticipated when the stapes is intact; pars tensa cholesteatoma with incus and/or stapes erosion is common. These factors reduce the applicability of IHA devices that require attachment to ossicles.

2.Recidivism: The high risk of recidivism in pediatric cholesteatoma threatens implant survival. While successful removal of residual disease can usually be assured at a second stage of surgery, continued follow up would be required for recurrent disease that may develop many years later. MRI screening for occult residual disease would be compromised by some devices.

3.Acceptability: Many teenagers do not wish to pursue rehabilitation for moderate unilateral hearing loss. It is conceivable that a totally implantable IHA, or a device with an inconspicuous external component hidden in the hair would prove desirable. Currently available totally implantable devices require ossicular attachment.

4.Expense: The cost utility of IHA for unilateral hearing loss has yet to be established in this population. Provision of binaural hearing at this formative social and educational stage of life may prove to have additional benefits beyond those that these candidates would continue to experience in adult life. The prospect of many decades of benefit will also make QALY measures appear more favorable.

These considerations reduce the number of children with cholesteatoma in whom IHA is appropriate, but there are children (most of them teenagers) with stable outcomes who could potentially benefit from a device that does not require anchorage to the ossicular chain. Ultimately, a long lasting affordable totally implant-able hearing aid may prove to be the optimum rehabilitative option for the majority of children following cholesteatoma treatment.


Address for correspondence: Adrian James, adr.james@utoronto.ca

Cholesteatoma and Ear Surgery – An Update, pp. 293–296

Edited by Haruo Takahashi

2013 © Kugler Publications, Amsterdam, The Netherlands