الرئيسية Otolaryngology - Head and Neck Surgery Cochlear implant in the child under two years of age: Skull growth, otitis media, and selection
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Cochlear implant in the child under two years of age: Skull growth, otitis media, and selection RONALDA. HOFFMAN,MD,New York, New York Early cochlear implantation is desirable to effect maximal development of receptive and expressive language. Factors to consider in implanting before the age of 2 years include anatomic considerations, temporal bone growth and device extrusion or migration, the sequela of otitis media, and the accuracy of early diagnosis. Clinical experience and laboratory data indicate that cochlear implantation before the age of 2 years is possible. (Otolaryngol Head Neck Surg 1997;117:217-9.) T h e goal of cochlear implantation in young children is to provide audition adequate to allow for the development of receptive and expressive language. The current lower age limit for cochlear implantation, 2 years, set by the Food and Drug Administration (FDA), may deny children critical auditory information during a period when the central nervous system is maximally responsive to stimulation. The National Institutes of Health Consensus Conference Panel on Cochlear Implants in Adults and Children, 1 convened in 1995, noted, "Children receiving implants at younger ages are on average more accurate in their production of consonants, vowels, intonation and rhythm . . . . A younger age of implantation may limit the negative consequences of auditory deprivation and may allow more efficient acquisition of speech and language." At present the only indication for surgery under the age of 2 years is impending cochlear ossification after meningitis. Ossification makes complete surgical implantation of a multichannel electrode array difficult, possibly leading to decreased performance. 2 Given the desh'e to achieve maximal performance, surgical implantation before the age of 2 years would From the Department of Clinical Otolaryngology, New York University School of Medicine. Presented at the Sixth Symposiumon CochlearImplantsin Children, Miami Beach, Fla., Feb. 2-3, 1996. Reprint requests: Ronald; A. Hoffman,MD, Department of Clinical Otolaryngology, Otology, and Neurotology,New York University School of Medicine, 530 First Ave., New York,NY 10016. Copyright © 1997 by the American Academy of OtolaryngologyHead and Neck Surgery Foundation, Inc. 0194-5998/97/$5.00 + 0 23/1/75095 be desirable. Several factors must be considered in determining the acceptable lower age limit for implantation. ANATOMIC CONSIDERATIONS Clinical experience and laboratory studies 3,4 suggest that, anatomically, implant surgery is feasible before 2 years of age. The labyrinth, into which the electrode array must be placed, is fully formed at birth. The middle ear is of near-normal size, with a minimal increase in depth attained by the sixth month of postnatal life as a result of development of the tympanic bone and an associated change in the plane of the tympanic membrane relative to the skull base. The facial nerve is in its normal position at the second genu at birth. This renders a facial recess of near-adult size. The descending portion of the facial nerve, which exits the immature mastoid process laterally, assumes a more normal vertical position as the mastoid process develops. The petrous and squamous portions of the temporal bone undergo their most rapid development during the second year of life. The mastoid process, on the other hand, has two growth spurts: one that plateaus by age 7 years and another near puberty. Skin thickness overlying the implant may be an important factor in young children. This can be addressed by seating the electronics in a deep well, exposing dura if necessary. No complications have been reported that are attributable to this "deep seating" technique. 5 Fortunately, the adequacy of any given child's anatomy can be assessed accurately before surgery with computed tomography. Anatomy per se, therefore, should not be an impediment to early implantation. 217 OtolaryngoiogyHead and Neck Surgery September 1997 218 HOFFMAN TEMPORAL BONE GROWTH AND DEVICE EXTRUSION/MIGRATION Temporal bone growth continues through adolescence. Eby and Nadol ]4 demonstrated that from age 1 year to adulthood the average mastoid in males can be expected to grow 2.6 cm in length, 1.7 cm in width, and 0.9 cm in depth. The average mastoid in females will grow 2.0 cm in length, 1.7 cm in width, and 0.8 cm in depth. These authors suggest that 2.5 cm of electrode redundancy is necessary in the mastoid to accommodate for head growth and avoid electrode extrusion from the cochlea. The Nucleus device has 7.6 cm of electrode redundancy in the mastoid, whereas the Clarion has 8.0 cm. Various surgical techniques have been developed to prevent receiver-stimulator extrusion and electrode migration. Migration or extrusion of the receiver stimulator can be avoided by drilling an adequate well and securing the device with nonabsorbable sutures, anchored in bone. Electrode migration out of the cochlea can be avoided by anchoring the electrode array distally, near the cochleostomy. Most surgeons pack the cochleostomy and facial recess with soft tissue. Nedzilski (personal communication) has described the use of a nonabsorbable suture to anchor the electrode to the incus bar. Balkany (personal communication) creates a "slot" in the incus bar to fix the electrode array. Cohen and Kuzma 6 have developed a titanium clip that is "crimped" to the incus bar and has a slot that cradles and gently fixes the electrode. The efficacy of these procedures has yet to be established with clinical studies. Nonetheless, evaluation of data regarding Complications for the Nucleus device 5 reveals the incidence of electrode migration out of the cochlea to be the same for adults (1.17% of 3064) and children (1.31% of 1905)' whereas the incidence of migration of the device is lower in chikh'en (0.05% of 1905) than adults (0.26% of 3064). OTITIS MEDIA AND SEQUELA An early concern of cochlear implantation in children was the possibility of an increased incidence of otitis media in children with implants and the migration of the offending organism along the electrode array into the cochlea and perhaps even to the central nervous system. Clark et al. 7 studied the potential for spread of pathogens into the cochlea in an animal model, the cat. He concluded that a fibrous tissue sheath forms around the electrode during the first few postoperative weeks, effectively sealing the cochleostomy and acting as an effective barrier to the spread of infection. In a 1993 review of available clinical data for children with the Nucleus device (n = 756). Cohen and Hoffman8 found no increase in the incidence of otitis and no complications when otitis did occur, ACCURACY OF EARLY DIAGNOSIS Accurate diagnosis is essential if children under age 2 years are to undergo implantation. Frequency-specific evoked-response audiometry in conjunction with behavioral testing makes it possible to be highly accurate in determining the degree of hearing loss. A more difficult task. however, is establishing the young child's speech and language progress with proper amplification. In younger children the surgeon must rely on the impressions of experienced pediatric audiologists and speech and language therapists. Although such clinical "gestalt" has great value, objective means of measuring and documenting speech and language progress are necessary if children below 2 years of age are to become routine candidates for implantation. EXPERIENCE TO PRESENT Two cochlear implant systems are presently being used in children in the United States. The Nucleus 22channel device (Cochlear Corp., Englewood. Colo.) received FDA premarketing approval in 1990, and more than 3000 children have undergone implantation to date. The Clarion 16-electrode bipolar array (Advanced Bionics. Sylmar, Calif./ is presently being implanted under an FDA investigational protocol In addition to differences in speech processing strategy, these implants are of different dimensions. The Clarion device (31 mm x 25 mm x 6 ram) is 16 mm shorter, 1 mm narrower, and 1 mm thinner than the Nucleus device (47.75 mm × 26 mm x 7 mm). Although the Nucleus device is 1 mm thicker at its maximum, this thickness is only in the area of the receiver stimulator "can." The antenna is only 2 mm thick and the junction between the antenna and the receiver stimulator is flexible. The Clarion device is uniformly 6 mm thick and rigid. These differences in dimension may be significant in young children. The Clarion implant may necessitate a larger well to avoid device migration or flap complications. At present, there are no published data for the Clarion implant in young children or children under 2 years. Seventy-eight children under the age of 2 years have undergone implantation with the Nucleus device. 69 children between 18 and 23 months, and 9 children between 12 and 17 months (personal communication), There have been no surgical complications in this group. One child had facial nerve stimulation after device activation. The device was explanted and a new OtolaryngoiogyHead and Neck Surgery HOFFMAN 219 Volume 117 Number 3 Part 1 d e v i c e placed. Facial nerve stimulation persisted but was controlled with p r o g r a m modification. Three of the children w e r e difficult to program, two eventually conf o r m e d to expectation, and one did not have stimulation. D a t a on audition and speech and language acquisition are not yet available for m o s t o f these children. SUMMARY Clinical e x p e r i e n c e and laboratory data indicate that, technically, c o c h l e a r implantation b e f o r e age 2 years is an achievable goal. The primary limiting factor is establishing candidacy in the very y o u n g child. REFERENCES 1. NIH Consensus Development Panel on Cochlear Implants in Adults and Children. Cochlear implants in adults and children. JAMA 1995;274:1955-61. 2. Gibson WPR, Brown C, Everingham C, Herridge S, Rennie M, Steinberg T. Necessity of early diagnosis and assessment of postmeningitis children in view of cochlear implantation. Ann Otol Rhinol Laryngol Suppl 1995;104:208-10. 3. O'Donoghue GM, Jackler RJ, Jenkins WM, Schindler RA. Cochlear implantation in children: the problem of head growth. Otolaryngol Head Neck Surg 1986;94:78-81. 4. Eby TL, Nadol JB. Postnatal growth of the hmnan temporal bone: implications for cochlear implants in children. Ann Otol Rhinol Laryngol 1986;95:356-64. 5. Hoffman RA, Cohen NL. Complications of cochlear implant surgery. Ann Otol Rhinol Laryngol Suppl 1995;t04:420-2. 6. Cohen NL, Kuzma J. Titanium clip for cochlear implant surgery. Ann Otol Rhinol Laryngol Suppl 1995;104:402-3. 7. Clark GM, Blarney PJ, Brown AM, et al. Biological safety. In: Pfaltz CR, editor. The University of Melbourne: Nucleus multielectrode cochlear implant: advances in oto-rhino-laryngology. NewYork: Karger, 1987. 8. Cohen NL, Hoffman RA. Surgical complications of multichannel cochlear implants in North America. In: Fraysse B, Deguine O, editors. Cochlear implants: new perspectives. New York: Karger, 1993:70-4. Endoscopic and Image-guided Sinus Surgery The Joint Center for Otolaryngology, Beth Israel Deaconess Medical Center and Brigham & Women's Hospital of Harvard Medical School, is sponsoring a course, "Advanced Endoscopic and Image Guided Sinus Surgery--Beyond the Basics," Nov. 7-8, 1997, at the Fairmont Copley Plaza in Boston. This course provides up-to-date, state-of-the-art information and instruction to the practicing otolaryngologist regarding advanced techniques in endoscopic sinus surgery. The use of endoscopics has significantly decreased the need for more invasive techniques, including the management of cerebrospinal fluid leaks and frontal sinus disease. Real-time imaging techniques, including the use of CT and MRI scanners, may hold the key to safer revision and frontal sinus surgery. Cadaver dissections with appropriate endoscopes and instruments will provide hands-on exposure to the various operations discussed. CT-guided sinus surgery will also be available during the laboratory session. For further information, contact Harvard MEDCME, EO. Box 825, Boston MA 02117-0826; phone (617)432-1525.