Cochlear Implants: A Surgeon’s Perspective

The issue

The past 25 years have seen great changes in the lives of deaf children.  In particular, neonatal hearing screening programmes have facilitated early intervention and enabled deaf children to capitalize on the receptiveness of the developing brain to sensory stimulation. Cochlear implantation also has found a place as a key intervention in the (re)habilitation of deaf children unable to benefit sufficiently from acoustical hearing aids. Still, some parents are anxious about implantation, largely due to stories and “warnings” from people who do not fully understand it.

What we know

In recent years, the internal components of implant systems have become better, and the electrodes are less likely than in the past to cause significant injury to the cochlea. The processing capacity of implants has increased exponentially, the external components are small enough to be worn at ear level, and batteries now last much longer than they used to – now for days at a time.  Candidacy for cochlear implantation also has changed. Early candidates were profoundly deaf with little to lose from implantation. Today, many children have some residual hearing (often in the low frequencies) which their parents are anxious to preserve. Their concern is well-founded as this residual, “natural” hearing helps children speech understanding and music perception; it is also important for the many speakers of tonal languages (like Cantonese). Bilateral simultaneous cochlear implantation (both ears) is now routine in many countries and has greatly enhanced outcomes by improving sound localization and a child’s ability to hear in noise (think classrooms!).  The implantation of children with disabilities in addition to their deafness also is now commonplace, and it is not unusual  to implant older teenagers who may have missed out earlier in life and feel the need to have access to additional hearing for educational or occupational reasons.

While the use of implants during bathing or swimming was forbidden in the past, some systems are now waterproof, overcoming this restriction. If an implanted child were to require surgical intervention for any reason, special requirements apply to the use of surgical instruments so as not to compromise the implant, but it’s very doable. Device failure is uncommon, but it is probable that a given device may need to be removed and re-implanted in an extended life-time. From what we know at present, this is technically possible without affecting hearing.

What we don’t know

The need for certainty regarding the degree of hearing loss in very young infants has never been more important. Overestimating a hearing loss could lead to inappropriate implantation and permanent loss of natural hearing – a great disservice to any child. We still are not very good at predicting how well any particular child will do with a cochlear implant. Careful testing therefore is essential before making the decision of whether or not to give a child and implant or, indeed, whether they might do better with a hearing aid.

There is still progress to be made. Improved speech perception in noise would be welcomed by most implantees and would greatly reduce the effort of listening in noisy classrooms. Better music reception would greatly enhance life-quality. While all surgeons endeavor to minimize injury during implantation, it is still a surgical procedure, and it is hoped that robotic-assisted insertions soon will minimize the possibility of damage during the implantation. We are also likely to see much greater emphasis on detailed pre-operative imaging to plan exactly how electrode arrays will be inserted.  There is considerable research interest in using drugs that reduce inflammation within the cochlea caused by the surgical procedure, and gene therapies may have an important part to play in conserving the cochlea’s sensory assets – an  important consideration given that today’s young implantees can anticipate a century of use from their implant systems.

Implications

Patient safety is the primary concern of all surgeons and it is now clear that implantation is safe with few significant risks. There are few restriction on a child’s life-style but certain events, such as MRI scanning or undergoing surgery need special precautions.  The surgery is now undertaken with even greater finesse than was the case in past as so as to preserve any natural hearing a child may have. Research in inner ear biology is likely to produce new findings that will positively impact on how the surgical procedure is undertaken in the future and improve outcomes even more. The overall message, therefore, is one of reassurance to prospective parents, that while surgeons have perfected their techniques from past experience, they are eager to do even better in the future.

Posted on January 12, 2015 by
Gerard M. O’Donoghue
National Institute of Health Research
Nottingham Hearing Biomedical Research Unit
Nottingham University Hospitals, Nottingham, United Kingdom
Gerard.O’Donoghue{at}nottingham.ac.uk

Further reading

Davidson, K., Lillo-Martin, D., & Chen Pichler, D. (2014). Spoken English language development among native signing children with cochlear implants. Journal of Deaf Studies and Deaf Education, 19, 238-250. view details

Sarant, J. & Garrard, P. (2014). Parenting stress in parents of children with cochlear implants: Relationships among parent stress, child language, and unilateral versus bilateral implants. Journal of Deaf Studies and Deaf Education, 19, 85-106. view details

Spencer, L., Tomblin, J.B., & Gantz, B.J. (2012). Growing up with a cochlear implant: education, vocation, and affiliation. Journal of Deaf Studies and Deaf Education, 17, 483-498. view details