Two ears are better than one. We fit eyeglasses in pairs. (Monocles went out of style with Peter Wimsey.) We routinely think about fitting bilateral hearing aids on kids. Research clearly demonstrates that two ears are a big help in noisy situations and in locating the source of sound. It has taken much longer to get this going for cochlear implants. A recent article in the Hearing Journal reports that parents and researchers are advocating for bilateral cochlear implants. The article gives some parent reports in which they talk about their observations about their children’s responses after getting a second implant. They describe an increase in spoken language skills and improvements in sound localization and hearing in noisy environments.
How often are bilateral implants performed?
As of 2010, the statistics from NIDCD indicated that more than 40,000 adults and nearly 26,000 children had received implants. Bilateral implants are less common. The last reported statistics on bilateral implants were in 2007, and at that time between 6000 and 7000 people had received bilateral implants. Discussion with people working in implant centers indicate that the number of bilateral implants is increasing, but the exact numbers are unknown.
Effects of cochlear implants on language
A recent study in Archives of Otolaryngology (Arch Otolaryngol Head Neck Surg 2012;138[2]:134.) demonstrated a significant improvement in quality of life with bilateral implants. It is more difficult to demonstrate the effect on speech and language. There is a dramatic improvement in speech and language after one implant so the effect is smaller after the second. The improvement in ability to hear in noise may have the best effect on improving language because it results in more language exposure.
Spatial hearing
Dr Ruth Litovsky, director of the Binaural Hearing and Speech Lab at the University of Wisconsin, has been studying outcomes of patients with bilateral implants for many years. Her group has found that CI’s improved spatial hearing in children even if they received their second implant several years after the first (Otol Neurotol 2010;31[8]:1287.) She reported that children who received their second implant within 3-5 years were more likely to have speech perception scores in the second implanted ear catch up to the first implanted ear than children whose second CI was activated at 5-8 years, and even more so than those implanted at 8-13 years. Litovsky’s group has demonstrated that children with bilateral implants can use information about sound localization to separate speech from noise better than those with just one CI. This is a very useful skill to have in a noisy classroom.
The earlier the better
Some families seek bilateral implants for their kids as soon as possible, and others want to wait hoping technology will improve before getting the second implant. I can tell you from my clinical experience that when there is a long time between receiving implants, many kids end up preferring the first ear and have better speech perception in that ear, although their bilateral speech perception is usually better than it is in each ear alone. They also do better in noise.
Kids who get their implants relatively close together do well with both ears. As we know, the earlier children get better hearing, the better their chance is of having normal speech and language development since they will have a shorter period of auditory deprivation. So, the earlier the better. Yes, the newer technology has advantages, but there are an awful lot of people with implants they received 20 years ago who are doing beautifully with them and hear as well as kids with current technology. Don’t wait, do it now.
