Safe Medical Devices for Children (2006) / Chapter Skim
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Appendix F Cochlear Implants in Children A Review of Reported Complications, Patterns of Device Failure, and Assessment of Current Approaches to Surveillance
Appendix F Cochlear Implants in Children A Review of Reported Complications, Patterns of Device Failure, and Assessment of Current Approaches to Surveillance
Pages 382-421
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From page 382... ...
Cochlear implants could potentially affect the auditory rehabilitation of an estimated 200,000 United States children with advanced levels of deafness as indicated by a failure to achieve critical milestones in speech and language using conventional hearing aids. While the impact of hearing loss in an adult varies considerably with the severity of hearing loss and with lifestyle choices, the impact of an advanced level of hearing loss in infancy and early childhood can dramatically affect developmental learning.
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It is estimated that approximately 7,500 to 10,000 United States children have received a multichannel cochlear implant prior to the age of 5 years out of
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384 SAFE MEDICAL DEVICES FOR CHILDREN FIGURE F.1 Ear-level processor. (Courtesy of Cochlear Americas Corporation.)
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APPENDIX F 385 FIGURE F.3 An implanted receiver and electronics package. (Courtesy of Ad vanced Bionics Corporation.)
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386 SAFE MEDICAL DEVICES FOR CHILDREN FIGURE F.5 An implanted electronics and receiver package connected to an electrode ray, which is inserted through the cochlea. (Used with permission of Lippincott Williams & Wilkins.
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APPENDIX F 387 · to the extent that a cochlear implant can encode the sounds of speech with precision, the device can provide opportunities for developmental and oral language learning in young children with implications for psychosocial development, scholastic achievement, and life chances; and · potentially dramatic, life-altering outcomes following early cochlear implantation have fostered high media visibility and enthusiasm about the benefits of early implantation. Against a two-decade old background of a generally positive global perception of clinical effects of cochlear implants in deaf children, a more open acknowledgement of potential harms has emerged in recent years.
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388 SAFE MEDICAL DEVICES FOR CHILDREN that are not statistically different from their normal-hearing peers. Likewise, Schauwers and colleagues12 found smaller delays in the onset of babbling with earlier implantation, and Govaerts and colleagues13 found that implantation before the age of 2 was important in achieving optimal results.
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APPENDIX F 389 those children who exhibited evidence of meningitic-related hydrocephalus. Data from this case series of 30 meningitis-deafened children suggest that central factors hold sway in predicting audiologic performance and that ossification of the cochlea does not prevent good outcomes.
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390 SAFE MEDICAL DEVICES FOR CHILDREN cation) is critical for surgical planning and for patient and family counseling before implantation.
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APPENDIX F 391 absence of fluid within the cochlear turns and the size of the cochlear and vestibular nerves within the internal auditory canals. MRI is superior to HRCT in determining cochlear obstruction due to non-ossified scarring.
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392 SAFE MEDICAL DEVICES FOR CHILDREN ies have, in fact, suggested no significantly heightened risk in the pediatric population. In a series of 309 children who were implanted with the Nucleus device by 25 surgeons in North America before 1991, the total complication rate (major and minor)
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APPENDIX F 393 necrosis secondary to magnet pressure.45 In older children, the lateral skull is usually thick enough to permit the creation of an adequate well for the receiver/stimulator. In younger children, in whom the skull is much thinner, the bone is often drilled to the level of the dura, or a mobile island of thin bone can be created over the dura in the center of the well for protection.
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394 SAFE MEDICAL DEVICES FOR CHILDREN most cases, ossification involves only the most basal portion of the cochlea, allowing complete electrode insertion.50 A significant if decreased number of neurons can also remain in ossification.51 El-Kashlan and colleagues52 and Steenerson and Gary53 therefore found that children with postmeningitic hearing loss and cochlear ossification could attain significant benefit from their implants, although children without ossification were likely to perform better. Still, other studies demonstrate that ossified and non-ossified children perform equally well.54 A key factor for success may be the timing of implantation.
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APPENDIX F 395 intracanalicular neural anatomy in detail.63 Histopathologic studies of temporal bones with cochlear malformations reveal substantially diminished and, in one case, bilaterally absent SGC populations.64,65,66,67 Even so, implantation of children with cochlear malformations can be achieved without surgical complications and can result in levels of performance comparable to patients with normal bony cochlear anatomy.60,68,69,70,71,72,73,74 Modifications of conventional surgical implantation techniques are suggested and depend on a knowledge of the different types of malformations. Malformations based on embryogenesis are described by Jackler and colleagues61 (Table F.1)
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396 SAFE MEDICAL DEVICES FOR CHILDREN TABLE F.1 Malformations Based on Embryogenesis as Described by Jackler and Colleagues (Images courtesy of Johns Hopkins Medical Institutions) Name (after Jackler et Other at.)
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APPENDIX F 397 Gestational Stage Anatomic at Developmental Axial CT Anatomy of Associations Arrest Cochlea & Labyrinth Often including Week 3 absence of IAC. Absence of Late week 3 promontorium distinguishes this from acquired ossified cochlea.
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398 SAFE MEDICAL DEVICES FOR CHILDREN percent of children with malformations by Mylanus and colleagues,76 though rates of up to 32 percent have been reported by Buchman and colleagues.74 Particularly in cases where the nerve crosses the promontory, Hoffman and colleagues warn of facial nerve paralysis and suggest a sacrifice of the posterior canal wall for better visualization in difficult cases.57 While Buchman and colleagues did not encounter either paresis or paralysis, they did note an association with adventitial facial nerve stimulation by the cochlear implant. CSF leak is also a common hazard when implanting children with inner ear malformations.
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APPENDIX F 399 Facial Nerve Injury Though rare, facial nerve injury is a serious potential complication of cochlear implantation. Studies focusing specifically on the incidence of injury in children are still lacking, but Hoffman and Cohen found a rate of facial nerve injury of 0.58 percent in 1,905 children.110 House and Luxford82 described eight cases, three of them pediatric, of facial paralysis or paresis that occurred after implantation.
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400 SAFE MEDICAL DEVICES FOR CHILDREN operative cases treated successfully and without any complications. Fayad and colleagues86 also found a significant decrease in cases of otitis media after implantation, both in children with and without a history of bilateral myringotomy and tubes, and Kempf and colleagues87 found only a 5.6 percent post-implantation rate of AOM.
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APPENDIX F 401 of risk did not suggest the need for positioner removal unless repeated infections of any kind are encountered. Since then, continued studies have revealed a higher risk for the disease in patients with all cochlear implants compared to the general population.
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402 SAFE MEDICAL DEVICES FOR CHILDREN cochlear implantation may already be at increased risk for meningitis particularly in the context of a CT-evident cochlear anomaly. Mechanisms for post-implantation meningitis for children with implants have been proposed by Cohen and colleagues.96 Infections may result from the direct spread of otitis media into the scala tympani, either at the time of surgery in immediate cases or some time following surgery in delayed cases.
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APPENDIX F 403 while implantation did not abolish vestibular function, temporary disturbances were seen in 20 percent of patients,104 thus yielding the possibility of post-implantation disequilibrium and vertigo. During the first week after surgery, patients often experience some degree of disequilibrium and unsteadiness.
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404 SAFE MEDICAL DEVICES FOR CHILDREN oblique incision.46 Of their 23 pediatric cases, no major complications occurred, and only 3 instances of wound edema were encountered. As Cohen and Hoffman warn,114 flaps that are too thick will impede the transmission of electrical signals, whereas flaps that are too thin will erode under the magnetic pressure.
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APPENDIX F 405 the normal SGC population ipsilateral to the implant (Zappia and colleagues) ,119 other studies in chronically implanted animals121,122 and humans123,124,125 showed no differences in SGC populations between the implanted and unimplanted ears.
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406 SAFE MEDICAL DEVICES FOR CHILDREN the implant case can result in dendrite formation and short circuiting of the safety mechanisms (e.g., capacitors) , which are designed to prevent neural overstimulation.
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APPENDIX F 407 2001 (0.3 percent/year) is approximately one-third of that associated with its first generation device used from 1985 to 1998 (0.8 percent)
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408 SAFE MEDICAL DEVICES FOR CHILDREN rate of device failure, these precautions may help to shield the device from traumatic events. Should device failure occur, though, reimplantation is the most viable solution.
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APPENDIX F 409 age of 19 months demonstrated faster progress and higher scores than those implanted between the ages of 2 and 3.140 As Geers142 found, though, this age advantage disappears after 2 years, implying a critical period of development within the first 2 years of life. At older ages, then, other factors begin to affect implant performance.
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410 SAFE MEDICAL DEVICES FOR CHILDREN Cheng and colleagues150 have demonstrated considerable quality of life gains at reasonable costs, particularly when compared to other health care interventions. It is clear, however, that early cochlear implantation does not provide a "mainstream" educational and psychosocial developmental opportunity for all childhood recipients.
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More recently, FDA has developed partnerships with major health care organizations in the United States to promote reporting adverse events through this program, particularly those of a serious nature. In 1984 FDA implemented the MDR (Medical Device Reporting)
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This is not an insignificant source of cochlear implant surgeries for children in the United States. The specific requirements for device-related adverse event reporting are outlined in federal regulation at 21 CFR 803.
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Information such as patient age, date of implant, surgical approach and relevant surgical anatomy, prior surgeries, and characteristics of the implant center are often not included in the MAUDE reports. To be effective, the MAUDE database will need to be structured to provide detailed information on individual medical devices.
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414 SAFE MEDICAL DEVICES FOR CHILDREN promote high rates of information updating and thus relatively high access when compared with patient groups using other implants. The above experience underscores that some cochlear implant device users and their families appear to go without close, regular follow-up by a medical facility.
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REFERENCES 1Reis R Prevalence and characteristics of persons with hearing trouble: United States, 19901991.
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416 SAFE MEDICAL DEVICES FOR CHILDREN 19Francis HW, Pulsifer MB, Chinnici J, et al. Effects of central nervous system residua on cochlear implant results in children deafened by meningitis.
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APPENDIX F 417 42Xu J, Shepherd RK, Xu SA, Seldon HL, Clark GM. Pediatric cochlear implantation: radiologic observations of skull growth.
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418 SAFE MEDICAL DEVICES FOR CHILDREN 66Monsell EM, Jackler RK, Motta G, et al. Congenital malformations of the inner ear.
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APPENDIX F 419 90Antonelli PJ, Lee JC, Burne RA. Bacterial biofilms may contribute to persistent cochlear implant infection.
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420 SAFE MEDICAL DEVICES FOR CHILDREN 114Cohen NL, Hoffman RA. Complications of cochlear implant surgery.
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Safe Medical Devices for Children. Field M, and Tilson H, eds.
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