Cochlear implants in severe childhood hearing loss

Hearing loss can be devastating for a child, affecting their ability to develop speech and language skills (and therefore communicate), and possibly leading to learning problems and social issues.

While hearing aids undoubtedly help, in some cases the hearing loss is so severe that these interventions do not have the desired results. When this happens, a cochlear implant may actually restore hearing, allowing the patient to hear and speak just as well as someone who has not suffered hearing loss, says Dr Andre van Straten, an ear, nose, and throat surgeon at Mediclinic Cape Gate.

How a cochlear implant procedure works

• An implant is placed on the surface of the skull, just below the scalp, with a thin wire called an electrode array placed within the cochlea – the inner ear organ responsible for hearing.
• This wire then stimulates the nerve responsible for hearing, making it possible to send electrical impulses to the brain.
• Externally, a device similar to a hearing aid is fitted to the head with a magnet. This device is responsible for receiving sound and stimulating the implant. It can be upgraded every two years, so the patient can benefit from technological advances. However, whenever the patient is not wearing this external device, they won’t be able to hear.
• Rehabilitation is as much a part of the procedure as the actual surgery, as it allows the patient to make sense of these new and different sound signals.

The key to an optimal outcome, however, is to perform the implant as soon as possible, says Dr Van Straten. He cites a recent case, involving a bilateral implant on a one-year-old patient: “The little girl had severe hearing loss in both ears as a result of cytomegalovirus,” he says, explaining that this is one of the most common causes of deafness in babies. Typically, pregnant mothers pass the virus on to their unborn children and, although they’re not always born deaf, hearing loss may occur gradually over several years.

In this case, the patient had been fitted with hearing aids in both ears, but since the hearing loss was progressive, they were no longer having the desired effect. As a result, Dr Van Straten – together with the audiologist and the cochlear implant team – decided it was time for a cochlear implant. “We were privileged to be able to implant both sides at the same time. Very few medical aids cover a simultaneous implant, but in such cases the patient only has to undergo a general anaesthetic and surgery as well as rehabilitation with an audiologist once. What’s more, it means the patient is unlikely to develop a preference to hear with the one ear implanted earlier than the other.”

Early intervention

Dr Van Straten says the timing of this implant was critical. “The sooner the procedure takes place, the better the results. If the implant is undertaken before the child is one year old, they will likely hear just like any other child.” This is because an implant works by sending electrical impulses to the brain, which is able to translate them into sounds that can be understood. “If a child is born deaf, we need to perform the procedure before they are three years old – any later, and the hearing pathways between the ears and the auditory centre of the brain will never develop.”

That said, it is possible for implants to take place later in life, if hearing loss has happened over time and after hearing and speech has already developed. In fact, Dr Van Straten says his oldest cochlear implant recipient was aged 89 when he received his cochlear implant surgery. Implants are especially effective in these cases, he adds, because the individual would already have hearing pathways in place. However, the implant must take place within 10 years of the onset of deafness, or the hearing centre in the brain will be taken over by another function.

Because of the urgency of the procedure, Dr Van Straten recommends that all children undergo hearing screening early on. “Most people think this involves making a sudden noise, like clapping your hands, but it actually requires testing by an audiologist with specialist equipment.” Unfortunately, a lack of resources means this screening is not universally available in South Africa. As a result, most hearing impediments are only identified because parents have a concern; they may have noticed that their child doesn’t hear well, for example, or has a delay in speech development.

Cochlear implant is still not a common procedure in South Africa, says Dr Van Straten, even though there are many patients who may benefit from one. He attributes this to a lack of:

• Effective hearing screening and referral
• Awareness of the benefit of cochlear implantation
• Funding.

“Our unit, the Tygerberg Hospital Stellenbosch University Cochlear Implant Unit (TH-SU-CUI) is the biggest in South Africa,” he adds, “but we only perform around five to 10 procedures every month”.