------------------------------------------------------------------------------- TITLE: MULTICHANNEL COCHLEAR IMPLANTATION IN PEDIATRIC PATIENTS WITH TOTAL COCHLEAR OSSIFICATION SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: March 4, 1993 RESIDENT PHYSICIAN: Lane F. Smith, M.D. FACULTY: Chester L. Strunk, M.D. DATABASE ADMINISTRATOR: Melinda McCracken, M.S. ------------------------------------------------------------------------------ "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." INTRODUCTION Cochlear implantation is a relatively new and exciting therapy for those with profound sensorineural hearing loss who are unable to be helped with conventional hearing aids. Rapid progress in this field has led to advances in the implant devices. The single channel cochlear devices have been replaced by multichannel cochlear implant systems. Along with changes in the design of cochlear implants, there has also been changes in the indications and contraindications for using these devices. In the past, cochlear implants were limited to postlingually deafened adults. Recently these devices have been approved for use in prelingually deafened children. The Nucleus 22 Channel cochlear device (Cochlear Corporation, Englewood, Colorado), is the first multichannel implant approved by the FDA for use in children (June 1990). Bony sclerosis of the cochlea has been considered a contraindication to multichannel device implantation. However, Gantz et al, and Balkany et al, have reported successful insertion of multichannel devices in adults with partial to near total obliteration of their cochleas. We present 3 case reports of early multichannel experiences in children with total cochlear bony sclerosis. In addition, we wish to describe a simple method of partial, 8- 10 electrode, insertion of multichannel devices in completely ossified cochleas. SURGICAL PROCEDURE A large 4 cm semicircular postauricular incision is made beginning superior to the auricle and extending down to the tip of the mastoid. This scalp flap, along with the temporalis muscle is elevated to the spine of the Henle and external auditory canal. A simple mastoidectomy is performed. A 2.2 cm diameter circular area is drilled into the temporal bone just posterior to the mastoid cavity. This will house the receiver portion of the cochlear implant. The facial recess is opened and enlarged until good visualization of the round window is obtained. Using a 1.0 mm diamond burr, a hole is drilled 0.5-1.0 mm superiorly to the round window and at a 80-90 degree angle with respect to the plane of the medial wall of the mesotympanium. This hole is carried directly inward for a distance of 9-11 mm. This approximates the length of the basal turn of the cochlea. Eight (8) to ten (10) electrodes of the nucleus 22 cochlear device are inserted. We do not go any deeper then the 9-11 mm as there is a risk of drilling out of the basal turn of the cochlea and there is risk of entering the internal carotid artery. The Tympanic membrane, eustachian tube and ossicles of the middle ear are left intact. Fascia taken from the scalp-flap elevation is packed around the electrode coil to keep it in place. Two holes are drilled into the mastoid tip and the electrode coil is anchored in place. The receiver portion of the implant is anchored to the temporal bone with 4-0 prolene sutures in the standard manner. The postauricular flap is closed with deep interrupted sutures of 3-0 vicryl. The skin is closed with a running interlocking 4-0 chromic suture. A mastoid dressing is placed over the wound and left in place for 48 hours. No drains are necessary. CASE REPORTS Case #1 L.T. is a 14 year old white male who suffered profound bilateral hearing loss after an episode of meningitis at age 1 year 8 months. In September of 1983, at age 7, the patient underwent insertion of a 3M/House single channel device. CT scans showed bilateral cochlear ossification and a 3 mm hole was drilled into the left cochlea into which the device was placed. Initially he did not stimulate, but after wearing the device for 6 months he developed auditory stimulation. In 1986 the unit ceased to function and was surgically removed. A new single channel device was inserted into the same hole. Using the single-channel device, he successfully developed language and intelligible speech. On July 30, 1990, using the described procedure, a 9 mm hole was drilled into the right cochlea and 9 electrodes of the multichannel device were inserted. Six weeks postoperatively, the patient had successful auditory stimulation of the right ear. Case #2 J.S. is a 7 year old white male who developed profound bilateral hearing loss after contracting pneumococcal meningitis at age 1 year 9 months. In August 1985 a 3M/House single-channel device was implanted in the left ear. A CT scan at that time showed a completely ossified right cochlea and a partially ossified left cochlea. A 4 mm drill out was required for insertion of the single channel device in the left cochlea. Postoperatively the child did not have auditory stimulation at his initial 6 week trial. He was encouraged to wear the device and eventually stimulated at 6 months postoperatively. The patient developed speech and language with the single device. Speech for common nouns was 38% intelligible to a naive listener. Despite success with the single channel device, the patient's parents who are both physicians, asked that we attempt insertion of a multichannel device. CT scans taken at this time showed the right cochlea to be essentially completely ossified. As previously described, a 9 mm hole was drilled into the cochlea and 9 electrodes were inserted on August 13, 1990. At six weeks postoperatively, the patient successfully stimulated. At 8 weeks postoperatively, the wound developed a small amount of purulent drainage which was successfully treated with Augmentin. The patient has had no problems since then. Case #3 W.H. is a white female who had a normal childhood with appropriate development of speech and language until contracting meningitis at age 4, in June of 1988. Unfortunately she was left with bilateral profound SNHL. She suffered no other neurologic sequelae. After undergoing extensive audiologic testing at the Houston Ear Research Foundation, she was felt to be a candidate for cochlear implantation. CT scans showed bony obliteration of the cochlea bilaterally. On Sept. 19, 1989 a nucleus 22 cochlear device was implanted in the left ear using the previously described surgical technique. A 9 mm hole was drilled into the basilar turn of the cochlea and 9 electrodes were inserted. Post-operatively the patient did extremely well. At 6 weeks postoperatively an attempt at auditory stimulation was made. No stimulation occurred. A repeat CT scan showed the cochlear implant to be inserted 9 mm into the basilar turn of the cochlea. Although the patient did not initially stimulate, she was encouraged to wear the implant. After one year, the patient developed successful auditory stimulation. RESULTS Using the described surgical procedure, all patients had successful implantation of 9 electrodes of the multichannel cochlear device into their obliterated cochleas. No major surgical complications occurred. One minor complication occurred. This was a mild wound infection in patient J.S. and was successfully treated with augmentin. All patients developed successful auditory stimulation. Patients L.T. and J.S. had immediate success with auditory stimulation. Patient W.H. developed successful auditory stimulation after wearing the device for one year. Patient L.T. as expected had stimulation only from those electrodes which were inserted; numbers 12 to 22. He was finally set at Bipolar +3 with electrodes 14 to 18 activated. His preoperative and postoperative audiograms are shown in figures 1 and 2. His auditory MAP is shown in table 1. Patient J.S. had initial stimulation of electrodes 14 to 22. He was finally set at Bipolar +1 with electrodes 17 to 20 activated. His preoperative and postoperative audiograms are shown in figures 3 and 4. His auditory MAP is shown in table 2. Patient W.H. developed stimulation of electrodes 12 to 22. She was finally set a Bipolar +3 with electrodes 12 to 18 activated. Her preoperative and postoperative audiograms are shown in figures 5 and 6. Her auditory MAP is shown in table 3. DISCUSSION Meningitis is one of the most common causes of profound hearing loss in children and the most common cause of cochlear osteoneogenesis. Consequently, a significant percentage of children with deafness have total or near total bony obliteration of their cochleas. The House Ear Institute reported that 34% of the first 128 children implanted with cochlear devices were found to have some ossification. Previously, cochlear ossification was felt to be an indication for single channel device implantation. Multichannel device implantation was considered by most cochlear implant surgeons to be contraindicated in patients with an ossified cochlea. The 3M/House single channel device, which was the only FDA approved single channel device, is no longer available. The ability to insert the multichannel cochlear device into an ossified cochlea may be the only chance for hearing restoration in these patients. The surgical procedure described is a fairly simple and direct method of implanting the multichannel device into an ossified cochlea. Using our method of drilling 9-10 mm into the basal turn of the cochlea, we were able to successfully implant 9 of the 22 cochlear electrodes into the cochlea in all three patients. This procedure has the advantages of using the standard facial recess approach and leaves the canal wall-up. A potential risk of this procedure is damage to the facial nerve. This risk is not thought to be significantly higher than the risk of facial nerve damage during cochlear implantation in a non-ossified cochlea. Another risk of this procedure is possible damage to the internal carotid artery. For this reason we are careful not to drill farther than 11 mm into the basal turn of the cochlea. In this study, no major complications occurred. The only minor complication that occurred was a wound infection which resolved promptly with oral antibiotic treatment. Facial nerve function was intact in all patients and operative blood loss was no different than routine cochlear implantation surgery in non-obliterated cochleas. Our procedure permits only partial, 9-11 electrode, insertion of the nucleus 22 multichannel device. Previously, Gantz et al., described a method of multichannel cochlear implantation into ossified cochleas in three adults. They described a complicated surgical procedure which involved a canal wall-down radical mastoidectomy and the drilling of a trough around the bony modiolus. Using this procedure they were able to insert all 22 electrodes. In their series of three adults, two developed successful use of the cochlear implant and the third did not. It seems reasonable to assume that this later approach, while allowing for total insertion of the cochlear implant, is more difficult, and more risky in terms of possible damage to the facial nerve and internal carotid artery. In addition, this procedure has the added disadvantage in that it necessitates a canal wall- down mastoidectomy and closure of the eustachian tube and external auditory canal. While it is theoretically preferable to have complete insertion of all 22 electrodes, even patients who have complete insertion of 22 electrodes often only use part of them for auditory stimulation. All three patients in this study developed successful auditory stimulation with the multichannel cochlear implant. The two patients who had immediate successful stimulation with the multichannel implant (J.S. and L.T.) had both had previous successful, although delayed, stimulation with the single channel devices in the opposite ear. Whether this improved their chances of hearing with the multichannel device is not known. The third patient (W.H.) developed successful auditory stimulation after one year. All three patients are currently actively using the multichannel devices in their daily lives and have developed adequate hearing. (See figures 1-6 and tables 1-3.) Successful use of a cochlear implant depends on the presence of sufficient numbers of auditory neurons to carry information received from the electrical signals of the implant to the cochlear nuclei. The effect of osteoneogenesis of the cochlea on the survival of these neurons remains uncertain. The single channel device has proven to be useful in developing hearing and speech in children with obliterated cochleas. Two of the cases presented here (J.S. and L.T.) both developed hearing and speech with a single channel implant. It is not known whether a multichannel device is superior to single channel device in an ossified cochlea. Because the multichannel devices provide spectral or place information in addition to temporal coding, it is hoped that patients J.S. and L.T. will be able to improve their auditory and speaking ability using the multichannel cochlear device. CONCLUSIONS 1. Labyrinthitis ossificans should not be contraindication to partial insertion of multichannel cochlear devices. Since FDA approved single channel devices are no longer available, this may be the only chance for hearing restoration. 2. Children with profound sensorineural hearing loss and intracochlear ossification will probably benefit from insertion of a multichannel cochlear device. 3. The procedure described for insertion of the multichannel cochlear device into ossified cochleas appears to be safe and effective. However, insertion of multichannel cochlear devices in patients with cochlear ossification should only be performed by surgeons experienced in cochlear implantation. 4. It is not known whether the multichannel cochlear devices are better than single channel devices in patients with ossified cochleas. ------------------------------------------------------------------------------- BIBLIOGRAPHY 1. Balkany T, Gantz BJ, et. al. Multi-channel Cochlear Implants in Partially Ossified Cochleas. Ann Otol Rhinol Laryngol 1988;97 (Suppl 135):3 2. Clough S, Luxford WM, et. al. The Narrow Internal Auditory Canal in Children: A Contraindication to Cochlear Implants. Otolaryngol Head Neck Surg 1989;100:227. 3. Clark GM. The University of Melbourne/Cochlear Corporation (Nucleus) Program. Otolaryngol Clin North Am 1986;19:329-54. 4. Ariyasu L, Galey FR, et. al. Computer-generated three-dimensional reconstruction of the cochlea. Otolaryngol Head Neck Surg 1989;100:87. 5. Gantz BJ, McCabe BF, Tyler RS. Use of Multichannel Implants in Obstructed and Obliterated Cochleas. Otolaryngol Head Neck Surg 1988;98:72-81. 6. Waltzman SB, Cohen NL, et. al. The Prognostic Value of Round Window Electrical Stimulation in Cochlear Implant Patients. Otolaryngol Head Neck Surg 1990;103:102. 7. Gantz BJ. Issues of Candidate Selection for a Cochlear Implant. Otolaryngol Clin North Am 1989;22:239-47. 8. Parkin JL, Stewart BE, et. Al. Prognosticating Speech Performance in Multichannel Cochlear Implant Patients. Otolaryngol Head Neck Surg 1989;101:314. 9. Luxford WM, House WF. Cochlear Implants in Children: Medical and Surgical Consideration. Ear Hear. 1985;6:205-35. 10. Webb RL, Clark GM, et. al. The Biologic Safety of the Cochlear Corporation Multiple-electrode Intracochlear Implant. Am Journ Otology vol.9, num. 1;1988:8-13. 11. Levine SC. A Complex Case of Cochlear Implant Electrode Placement. Am Journ Otology vol. 10,num. 6;1989:477-80. 12. Mueller DP, Dolan KD, Gantz BJ. Temporal Bone Computed Tomography in the Preoperative Evaluation for Cochlear Implantation. Ann Otol Rhinol Laryngol 98;1989:346-49. 13. Jackler RK, Luxford WM, et. al. Cochlear Patency Problems in Cochlear Implantation. Laryngoscope 97;July 87:801-805. 14. Cohen NL, Hoffman RA, Stroschein M. Medical or Surgical Complications Related to the Nucleus Multichannel Cochlear Implant. Ann Otol Rhinol Laryngol 97;1988:8-16. 15. Chute PM, Hellman SA, et. al. A Matched-Pairs Comparison of Single and Multichannel Cochlear Implants in Children. Laryngoscope 100;Jan 1990:25-28. 16. Novak MA, Fifer RC, et. al. Labyrinthine Ossification After Meningitis: Its Implications for Cochlear Implantation. Otolaryngol Head Neck Surg 1990;103:351. 17. Steenerson RL, Gary LB, Wynens MS. Scala Vestibuli Cochlear Implantation for Labyrinthine Ossification. Am Journ Otology vol. 11, num. 5;Sept. 1990:360-363. -----------------------------------END-----------------------------------------