You can never be too young or too thin, the saying goes. But in the case of cochlear implant (CI) surgery, just how young can a patient with profound hearing loss be—and still qualify as a viable and safe candidate for the procedure?
Explore this issue:August 2012
The FDA has recognized that there are risks associated with CIs in younger patients. For example, the general anesthesia required by the surgery has been linked to the development of long-term learning disabilities (Anesthesiology. 2009;110:796-804). Partly due to these risks, CI surgery has been approved by the FDA in the U.S only for children 12 months of age or older. But in Italy, a team of pediatric specialists is pushing the age envelope and implanting children as young as two months of age. They are reporting, for the first time, that the procedure can yield significant improvements in speech perception and several other auditory outcomes, with little to no risk to these younger patients (Otolaryngol Head Neck Surg [published online ahead of print March 27, 2012]).
The rationale for performing CI surgery in infants has a logical basis in physiology, according to Vittorio Colletti, MD, a surgeon in the ENT department at the
University of Verona, Italy, and senior author of the new study. “At birth, the auditory sensory mechanism of the human neonate is fully functional and ready to establish neural connections based on auditory experience,” wrote Dr. Colletti and his colleagues in the study. “Early language exposure, through social interaction, shapes the developing nervous system. Without this, linguistic ability diminishes quickly, and only early access to language”—for example, via CI implantation—“provides a profoundly deaf child an opportunity to develop within the normal continuum.”
To assess whether CIs can indeed help patients achieve that normal continuum of hearing, the investigators focused on a group of 45 patients culled from 386 children who received the implants from Dr. Colletti and his team of pediatric specialists. Of those 45 patients, 12 infants were aged two to six months (Group 1), nine were aged seven to 12 months (Group 2), 11 were aged 13 to 18 months (Group 3) and 13 were aged 18 to 24 months (Group 4).
A wide range of pre-implant audiologic and radiologic assessments was performed in all of the study patients to ensure that CI surgery was an appropriate therapeutic intervention. The tests included otomicroscopy, tympanometry, acoustic reflex thresholds and click auditory brainstem response threshold assessments, as well as computed tomography, magnetic resonance imaging and and pediatric and neuropsychiatric evaluations, as needed.
The patients who received CIs did so with parental informed consent and as soon as an accurate diagnosis was obtained and all pre-operative surgical protocols had been completed, Dr. Colletti and his team reported. Patients’ hearing function was assessed at regular intervals throughout the 48-month period of post-implant follow-up.
Dr. Colletti stressed to ENT Today that additional in-depth electrophysiological evaluations were performed in order “to obtain the correct information on the hearing levels [in children] under six months of age.” Such testing, he noted, helped to ensure that children were optimal candidates for CI surgery.
The mean age of the patients in Group 1 (3.9 months) “is the lowest described in the literature,” Dr. Colletti reported. And in those infants, some of the most impressive results were observed. For example, speech perception scores in Group 1, as measured by the Categories of Auditory Performance (CAP II) test, were statistically significantly higher than in all of the other implanted children, the investigators reported (P <0.001).
Moreover, both receptive vocabulary and speech production in the youngest group were comparable with a control group of normal-hearing children “and significantly better than growth rates achieved by children implanted after six months.”
The complications that occurred during the study were all deemed minor. For example, two children in the study (aged 13 and 24 months) experienced transitory bronchospasm and hypotension as a result of anesthesia. In both cases, the reactions resolved with medical treatment.
For Dr. Colletti, the results confirmed that infants younger than six months of age can be safely and effectively implanted and given a chance to achieve “their full [hearing and developmental] potential, offsetting the need to learn at a faster than normal rate to attain age-appropriate norms.”
The investigators stressed several important limitations to the study. First and foremost, they noted, was the small sample size of infants younger than six months of age who were fitted with CIs. Given those small numbers, they reported, it is difficult to generalize the low incidence of complications seen in that cohort. Moreover, the study was uncontrolled and observational and included “personal audiological
criteria and…limited support from the literature.” Given those limitations, they struck a cautious tone in their conclusion: “The data … must be considered explorative, necessitating a more extensive study.”
—Bruce Gantz, MD
Experts Voice Caution—and Concern
Blake Papsin, MD, director of the Cochlear Implant Program at the Hospital for Sick Children in Toronto, Ontario, said he appreciated the investigator’s conservative conclusions. But he voiced concern that some surgeons may nevertheless read the study and assume it supports a more aggressive approach to CI surgery in infants.
“That really would be unfortunate,” Dr. Papsin told ENT Today. “Dr. Colletti is a very experienced, talented surgeon who has access to a team of equally experienced pediatric audiologists and anesthesiologists, working at a top-notch center. So he can do this. But can most surgeons in North American and Europe achieve the same results? I’m just not sure. Yet my fear is that some will be emboldened to try this, based on the preliminary data in this study.”
Dr. Colletti told ENT Today: “We are sure that some researchers in the field will, in the very near future, try to replicate our study to confirm or contest our results on the basis of their own personal experience.”
Even if other clinicians could achieve similar outcomes, Dr. Papsin said, the initial benefits achieved may not hold up over time. Most children reach a normal speech acquisition curve by age two years, he explained. Implanting them at an age younger than six months “may move that up to around 18 months, maybe a bit better than that,” he said. “For that, you’re going to risk the downsides of doing this procedure in infants, such as the risks of anesthesia, a missed diagnosis, etc.? I don’t think that’s a good risk-benefit tradeoff.”
Bruce Gantz, MD, professor and head at the University of Iowa Department of Otolaryngology—Head and Neck Surgery, University of Iowa Hospitals and Clinics in Iowa City, said he also doubts the lasting power of the differences in speech acquisition documented in the study. “We just submitted a manuscript [to a leading scientific journal] showing that children who are implanted as late as four years have the ability to catch up to those implanted before the age of two, and that the ‘leveling out’ of some speech and language scores occurs at about age eight,” he told ENT Today.
Dr. Gantz said he also had some concerns about the design of the study by Colletti and colleagues. For example, he questioned why, after implanting nearly 400 children, the investigators included only a small group of older children in the study. Given the small size of the cohorts, he said, “I am not comfortable saying there really is a significant difference between the age groups. And I am certainly not comfortable concluding anything without longer-term follow-up.”
But for Dr. Gantz, there is a potentially larger issue at stake when one considers implanting infants who are younger than six months of age. “I very strongly disagree that you can implant a child before obtaining a behavioral audiogram, which you can usually do between seven and 10 months of age,” he said. Such tests, Dr. Gantz added, can detect the presence of residual low-frequency hearing, which can then be amplified with a hearing aid on one ear and a cochlear implant in the other ear. “That’s a far better way to manage these patients, because that dual approach preserves the patient’s ability to appreciate music and other important aspects of sound that cannot be reproduced by a cochlear implant alone,” he said.
“Can you implant children at 10 or 11 months of age? Sure—we do it and consistently achieve very acceptable results. But I don’t know of any other group, other than Dr. Colletti’s, [that] has shown that this procedure works in younger children,” said Dr. Gantz. “For me, if the child is not old enough to [undergo] a behavioral audiogram, I’m not even going to consider that patient to be a viable candidate for CI surgery.”
In the case of residual hearing, Dr. Colletti agreed “that a standard implant can destroy residual hearing in this population.” To protect against that outcome, “we performed routine intraoperative ECoG in all children during CI surgery,” he added.
For Dr. Papsin, there is one instance where patients younger than six months of age often receive a cochlear implant—in cases of post-meningitic deafness, “where the potential risks of intracochlear ossification drives us to operate early,” he said. But without that particular history of infectious disease, “I certainly would not let my child undergo an elective operation based on this low-level data.”
Disclosures: Dr. Papsin is a member of the Speakers Bureau of Cochlear Americas Corp., and Dr. Gantz is a consultant for Cochlear Corporation and Advanced Bionics.