Hearing impairment is a silent disease. It is often neglected, but its effects can be crippling. It isolates its victims and makes them socially or economically less productive. Approximately 360,0001 persons in Singapore suffer from hearing impairment, making it one of the most common conditions affecting Singaporeans.
Furthermore, congenital deafness is the commonest major birth defect in Singapore, with a local prevalence of 1.7 in 1000 newborns with severe to profound hearing loss and approximately 5 in 1000 born with less significant hearing loss.
As physicians, our patients look to us to help them break out of this realm of silence and integrate back into society. With new technologies rapidly coming online, a wide range of hearing restoration strategies is now available, and the most suitable intervention can be tailored for almost every individual’s hearing needs.
The clinical evaluation begins with an otological history that elucidates the temporal characteristics of the hearing loss, including its onset and progression, identifies risk factors for hearing loss such as family history and excessive noise exposure, and notes any associated complaints of vertigo and tinnitus.
Physical examination would include an otoscopy to examine the external and middle ear. Tuning Fork tests, such as Rinne’s and Weber’s, can suggest the pattern of hearing loss. To further characterise the type and severity of hearing loss, audiological investigations, such as pure-tone audiograms and speech discrimination tests, should be performed.
Imaging investigations such as CT and MRI scans help in determining the aetiology and anatomical extent of the disease.
The holistic management of hearing loss involves care for patients, their families, and caregivers. Often, the family initiates the consultation because they find caring for a family member with hearing loss frustrating. Successful hearing rehabilitation leads to greater family harmony and emotional well-being. The patient’s own aspirations for independence are also critical in management decisions, as some surgeries restore hearing without the need to wear hearing devices or enable patients to achieve better hearing when their existing hearing aids are inadequate.
If there is a surgically correctable cause of hearing loss (usually conductive), such as otosclerosis or ossicular chain abnormalities, the ideal solution would be to operate (e.g., stapedotomy or ossiculoplasty) to restore the patient’s hearing without the need for any assistive hearing devices.
Modern hearing aid amplification technology has become highly sophisticated. The new devices have advanced speech and signal-processing capabilities that allow them to program appropriate hearing amplification tailored to the patient’s hearing-loss pattern and environment. They are now much smaller and more powerful. Some are designed to be waterproof for use in watersports.
Open-fit hearing aids are a new delivery system that are more comfortable to wear, have less occlusion and feedback, and provide more natural sound amplification. Some hearing aids can even connect wirelessly with telephones!
Arguably, the most exciting field in hearing restoration today is surgical hearing implants. There are now myriad surgically implantable hearing devices that cater to almost every possible hearing need.
Cochlear implants provide direct electrical stimulation to the auditory nerve endings in the cochlea, thereby bypassing problems with the cochlear hair cells, which account for the majority of patients with sensorineural hearing loss.
According to the United States Food and Drug Administration, as of December 2010, approximately 219,000 people worldwide have received cochlear implants. Commonly referred to as a “Bionic Ear”, cochlear implants have significantly transformed the lives of countless families with children born deaf. These deaf children can now hear. No longer are parents told that their child cannot develop speech and language.
In fact, many of these children have gone on to outperform their normal hearing peers in mainstream education and contribute significantly to society. Nowadays, children as young as 6 months old are implanted, and the trend is towards bilateral cochlear implantation for better stereo sound localisation and performance in noisy environments. Many adults with bilateral severe to profound sensorineural hearing loss have also been implanted and have been able to return to their active, busy, independent lifestyles.
Combined Electric Acoustic Stimulation (EAS) is the concept of applying acoustic amplification and cochlear implant technology together in the same ear. EAS™ is a relatively new option for people with residual low-frequency hearing coupled with profound high-frequency hearing loss, often referred to as a ski-slope hearing loss.
Hearing aids often provide unsatisfactory results for understanding speech or listening to complex sounds, such as music, for such persons. Traditional cochlear implant systems do not allow users to benefit from their residual natural hearing of low-frequency sounds. The speech processor features acoustic amplification that supports a person’s natural residual hearing at low frequencies, and for higher-frequency sounds, the processor’s cochlear implant function automatically takes over. The result is a synergistic effect that offers the benefits of both types of hearing technology.
Active Middle Ear Implants are another new group of surgical implants. They augment or replace the ossicles’ sound-transmission capabilities. It comprises an internal component that is attached to a middle ear ossicle or to the round window, where it vibrates and provides direct mechanical drive and therefore increases the power of sound amplification of the ossicular chain.
It can be used in patients with mild to severe sensorineural hearing loss and in those with mild to severe mixed or conductive hearing loss. The external ear canal is left entirely open, thereby affording advantages over a hearing aid. It is more comfortable to wear and has no occlusion effect, so low-frequency sounds enter the ear naturally, giving better hearing in noisy environments; it has less feedback and provides better high-frequency gain.
Semi-implantable devices have small, cosmetically appealing, externally worn sound processors hidden in the postauricular hairline. Fully implantable versions have no externally worn components, resulting in even better cosmesis, and can be used when swimming or bathing.
Lastly, Bone Anchored Hearing Aids (BAHA) are a unique type of surgical hearing implant. They comprise a titanium abutment screw surgically anchored into the skull behind the ear. The external speech processor clips onto the screw and converts sound into mechanical vibrations that then vibrate the skull, activating the cochlea via bone conduction.
This has proven immensely beneficial to 2 main groups of patients. The first group includes patients with conductive hearing loss who are not able to wear conventional hearing aids, such as children born with microtia or atresia of the external ear canals, or patients with chronically discharging ears. The second group consists of those with single-sided deafness, in which sound can be transmitted from the deaf ear to the cochlea of the good ear via bone conduction. This reduces “blind spots” in hearing on the deaf ear’s side.
The gift of hearing is often taken for granted until it is lost. Thankfully, nowadays, you can help return that gift to your patients. A newly expanded armamentarium of surgical hearing implants, coupled with improved hearing aid technology, ensures that the overwhelming majority of your patients can hear well again.
References
Low WK. Managing hearing loss in children and adults: Singapore context. Ann Acad Med Singapore 2005;34(4): 295-300.
Low WK, Pang KY, Ho LY, Lim SB, Joseph R. Universal newborn hearing screening in Singapore: the need, implementation and challenges. Ann Acad Med Singapore 2005;34(4): 301-6.
McMurray JS. Hearing Screening in the newborn. Curr Opin Otolaryng Head Neck Surg 2000;8:465-8.
