The optimum age for cochlear implantation in children

A study funded by Deafness Research UK, and carried out by Dr Margaret Tait at The Ear Foundation in Nottingham, investigated whether the age of implantation affects how children progress.

[Project grant, 2004-2007]

Before young deaf children are given a cochlear implant, their communication tends to be mainly visual and silent. After implantation they are expected to become more vocal and to make more use of audition.

The original aim of the study was to compare three groups of children, implanted at the age of one, at the age of two and at the age of three, to see what progress they made in auditory processing of speech and to see if this changed the way they communicated.

The children were each videoed with a familiar adult, to see how often they responded vocally when they had not been in eye contact with the adult. A child who responds vocally to the adult in this way without being prompted visually, is making an auditory response as well as a vocal one.

Before implantation, there was very little of this auditory behaviour in any of the three groups. However, by 12 months after implantation, the group implanted at one were making auditory responses most of the time, whereas those implanted at two and three had shown very little change; this difference was highly significant.

Early implantation also influenced the way they communicated. Before implantation around 80% of all the three groups were using signed communication rather than vocalisations. Twelve months after implantation, the groups implanted at two and three had shown very little change, whereas of the group implanted at one, only 15% were still using signed communication, with the majority having moved to oral communication.

The study was extended to a younger age-group and a comparison was made between two groups of children, the first implanted under the age of 12 months, and the second consisting of age-matched normally hearing children. The results of this video analysis showed no significant differences between the deaf group and the normally hearing group where vocal initiative and non-looking vocal turns were concerned, both at the 6 month and 12 month intervals.

These results suggest that implantation under the age of 12 months gives children the opportunity to develop early preverbal vocal and auditory skills to an extent comparable with those of normally hearing children.

The results add decisively to a growing body of evidence that early intervention is strongly beneficial. The analysis method has been extended down to the youngest viable age group and has shown, in the case of cochlear implantation, that early implantation leads to pre-verbal communication skills that are near normal in several important respects. This is an important demonstration for several constituencies: parents, teachers, audiologists, and commissioners of health care.

Update

Since the study The Ear Foundation has incorporated the results into training courses on Tait Video Analysis of young deaf children’s progress. The results have also been used in a set of procedures known as NEAP (the Nottingham Early Assessment Package). NEAP is designed to assess communication and linguistic development in infants and is widely used in cochlear implant programmes and in other work with deaf children.

Results were published in the paper ‘Age at implantation and development of vocal and auditory preverbal skills in implanted deaf children’, which appeared in the International Journal of Pediatric Otorhinolaryngolgy in April 2007, by the authors Tait ME, Nikolopoulos TP and Lutman ME. 

Dr Tait is currently conducting a study to compare the pre-verbal communication skills of children with two cochlear implants to children of the same age who have just one