Implantation of the malformed cochlea

Complications in auditory brainstem implant surgery in adults and children

OBJECTIVE

Surgery for hearing restoration with auditory brainstem implantation (ABI) in patients with neurofibromatosis type 2 (NF2) is considered safe, as no increase in postoperative complications related to surgery or device implantation has been observed. Over the last 10 years, we have extended the use of ABI to nontumor (NT) adults and children with cochlear or cochlear nerve malfunctions who would not or did not benefit from a cochlear implant (CI). This article examines the complications encountered in ABI surgery in all patient groups.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

: One hundred fourteen ABI operations were performed in Verona (Italy) from 1997 to 2008 in 83 adults and 31 children. Thirty-six had NF2 (34 adults and 2 children), and 78 (49 adults and 29 children) had NT cochlear and cochlear nerve disorders.

INTERVENTION

A retrosigmoid-transmeatal approach was used in the NF2 cases, and a simple retrosigmoid approach was used in the NT patients.

MAIN OUTCOME MEASURES

Surgical complications are tabulated according to standard reporting categories and are presented separately and analyzed statistically for NF2, NT adults, and NT children. Complication rates are compared with those of CI and microvascular decompression surgery.

RESULTS

ABI surgery has a very low major complication rate, particularly in non-NF2 patients. Minor complications were easily controlled with complete resolution in all cases. Although the potential complications of intradural ABI implantation are more severe than those of a transmastoid approach for CIs, the actual observed complication rates in ABI candidates without NF2 tumors are comparable to those of CI surgery in both adults and children.

CONCLUSION

This study demonstrates that the ABI is a safe procedure when performed by an experienced surgical and rehabilitation team, and its benefits can be extended to a larger population of deaf patients.

Cochlear implantation in postlingually hearing-impaired adults: choosing the most appropriate ear

Choice of the most appropriate ear for CI in postlingually hearing-impaired adults is becoming more relevant as more patients are considered eligible for intervention. The aim of this study is to review factors that influence this choice and to formulate a flowchart. An extensive Medline search was performed. Factors can be divided into surgical, audiological, and patient factors. Surgical factors are anatomic variation and otological medical history. Both are divided in absolute and relative contraindications. Duration of deafness and residual hearing are combined in the audiological factor. Likeliness of improvement of speech perception after CI at different durations of deafness is estimated. This is followed by comparison of between-ear differences in duration of deafness. If there is a large difference, above the presented 5% interval, the ear with the shortest duration is preferred. This review and its flowchart are an aid for decision making in the choice of ear for CI. Being as representative of current knowledge as possible, future refinements may occur as new insights are gained.

Complications following cochlear implantation in patients with anomalous inner ears: experiences in Asan Medical Center

CONCLUSION

Although the rate of postoperative complications was higher in patients with anomalous inner ears than in patients with normal inner ears, most were minor and could be managed conservatively. These findings suggest that cochlear implantation (CI) is safe even for patients with anomalous inner ears in experienced hospitals.

OBJECTIVE

To report complications encountered in patients with various types of anomalous inner ears undergoing CI in Asan Medical Center.

PATIENTS AND METHODS

We retrospectively analyzed 388 patients who underwent CI between April 1999 and July 2006; of these, 80 patients had various inner ear anomalies. Immediate complications were defined as those occurring within 1 week of implantation and delayed complications as those occurring after 1 week. Minor and major complications were defined by severity requiring further management.

RESULTS

Of the 80 patients with anomalous inner ears, 20 cases (25.0%) had postoperative complications, including 5 (6.3%) with major complications: facial nerve palsy, recurrent meningitis, device failure, and cerebrospinal fluid (CSF) leakage. Re-implantations were performed in three patients (3.8%).

Audiological performance after cochlear implantation: a 2-year follow-up in children with inner ear malformations

CONCLUSIONS

Open-set speech perception in children with an inner ear malformation is equal to that of other congenitally deaf children after an average of 2 years follow-up.

OBJECTIVE

To analyze audiological performance after cochlear implantation in a sample of children with radiographically detectable malformations of the inner ear compared to performance in prelingually deafened children at large.

MATERIALS AND METHODS

Nine children with osseous inner ear malformations were compared to 22 congenitally deaf children, all of whom underwent cochlear implantation. All subjects were tested on their electrical evoked compound action potential. Speech perception tests were performed using the monosyllabic trochee polysyllabic test without visual support and the open-set monosyllabic wordlist.

RESULTS

In all, 20% of the congenitally deaf children in our center study have inner ear abnormalities. Inner ear malformations were limited to incomplete partition of the cochlea; none of the subjects had common cavity malformations. Electrical compound action potentials were successfully recorded in both groups intraoperatively. Speech perception tests on open-set speech yielded an average of 48.8% (SD 21.2%) in the group of children with inner ear malformations vs 54.5% (SD 21.1%) in congenitally deaf children. In four of nine cases with an inner ear malformation we encountered a minor CSF leak.

Surgical Results of Cochlear Implantation in Malformed Cochlea

OBJECTIVE

To report the surgical aspects of cochlear implantation in malformed cochlea.

SETTING

Tertiary care center.

STUDY DESIGN

Retrospective case review.

METHODS

Between November 1997 and October 2004, 20 patients with inner ear malformations were implanted in our department. The age range was between 2 and 37 years (average, 8.8 yr). The anomalies were classified according to Sennaroglu and Saatci classification. There were two patients with common cavity deformity, four cases of incomplete partition (IP) type I (cystic cochleovestibular malformation), four cases of IP type II (classical Mondini's deformity), nine patients with large vestibular aqueduct (LVA) syndrome, and one patient with X-linked deafness.

RESULTS

Standard transmastoid facial recess approach was used in 17 patients (three patients with IP I, four patients with IP II, and nine patients with LVA syndrome). In the remaining patient with IP I, because of the dehiscent and anteriorly located facial nerve, the surgical approach had to be modified, and an anteroposterior approach was used. After elevating the tympanomeatal flap, the electrode was inserted through the ear canal and then transferred to the mastoid through a full-length cut produced in the ear canal. The flap then returned to its place. In the patients with common cavity deformity, the electrode was inserted by the transmastoid labyrinthotomy approach. Facial nerve had an abnormal course in four patients, but no patient had facial weakness postoperatively. Cerebrospinal fluid gusher was encountered in four patients, whereas oozing was present in five patients. It seems that a slightly larger cochleostomy may reduce postoperative rhinorrhea. The patient with common cavity deformity showed abnormal vestibular stimulation which decreased and was totally abolished during a 3-month period.

CONCLUSION

Based on these findings, cochlear implantation is surgically feasible in patients with common cavity, IP types I and II, and LVA. The surgeon should be ready to make modifications in the surgical approach because of the abnormal course of the facial nerve and be ready to produce special precautions to cerebrospinal fluid gusher.

Implante coclear en malformaciones congénitas

OBJECTIVE

The main objective is to evaluate the complications and problems encountered in a population with inner ear congenital malformation undergoing cochlear implantation.

MATERIALS AND METHODS

The present study includes 33 patients with congenital inner ear malformation, from a total population of 346 cochlear implant patients, implanted from February 1993 to March 2004. Radiological evaluation and neurological exams were performed to all these patients in order to evaluate all the preoperative conditions.

RESULTS

The most common cochlear anomalies we found were: cochlear hypoplasia, Incomplete partition and Common cavity (n=15). In 4 cases an enlarge aqueduct was also associated to the cochlear anomaly. We also found 6 cases with labyrinthine anomalies. The surgical procedure was performed in 23 cases, and in 18 of them we obtained an electrical stimulation of the neural elements.

CONCLUSIONS

There are no differences between patients with Incomplete Partition of the cochlea and mild Cochlea hypoplasia, if compared with those with normal cochlea. Severe malformations as Common Cavity or severe hypoplasia may have a higher rate of surgical complications and the outcome cannot be predicted.

Congenital malformation of the inner ear and pediatric cochlear implantation

OBJECTIVES

To study the surgical aspects and performance outcome of cochlear implantation in children with malformed inner ears.

STUDY DESIGN

Clinical and audiometric evaluation in 13 patients.

METHODS

Patient data concerning surgery, postoperative follow-up, and pre- and postimplantation audiometry were obtained from the cochlear implant center's database and evaluated. A review of the literature has been included.

SETTING

Tertiary referral center.

PATIENTS

The patients had a variety of inner ear malformations and profound hearing loss. One patient with recurrent meningitis had a severe cochlear malformation (common cavity).

RESULTS

Major complications did not occur. In one patient with an abnormal position of the cochlea and concurring middle ear disease, it was difficult to find the scala tympani during surgery. A cerebrospinal fluid gusher was encountered in two patients and an aberrant facial nerve in another, which did not lead to any complications. The patients with mild cochlear malformation such as an incomplete partition demonstrated a good performance in speech perception tests. Even the child with the common cavity deformity had some open-set speech perception 1 year after implantation.

CONCLUSIONS

Viewing the patients from this study and patients from a review of the literature concerning cochlear implantation in children with malformed inner ears including severe cochlear malformations, the occurrence of an aberrant facial nerve was 17%, which increases to 27% if one reviews the surgical findings in children with severe malformed cochleae such as a common cavity or a severe cochlear hypoplasia. In the latter patients, results in speech perception vary. Although the result of cochlear implantation may be promising, as in our patient with a common cavity, during preoperative counseling the child's parents must be informed that the result is uncertain.

Development of a novel eighth-nerve intraneural auditory neuroprosthesis

OBJECTIVES/HYPOTHESIS

Cochlear nerve stimulation using a linear array of electrodes, the cochlear implant, has become an accepted treatment for profound deafness. Major limitations of this technology are high threshold of stimulation, poor performance in a noisy background, cross-talk between electrodes, unsatisfactory channel selectivity, and variable reconstruction of frequency space. A novel auditory neuroprosthesis is proposed that is expected to overcome these problems by implanting an array of three-dimensional microelectrodes, the Utah Electrode Array, directly into the cochlear nerve.

STUDY DESIGN

We have conducted acute, extending for up to 12 hours and semichronic, extending for up to 52 hours, electrophysiological experiments, radiologic and histologic studies in 12 cats.

METHODS

The electrically evoked auditory brainstem response was used as a means to characterize the threshold, dynamic range, and stability of cochlear nerve stimulation through the implanted Utah Electrode Array neuroprosthesis. Plain film, computed tomographic, and histological studies were conducted to determine the result of the implant.

RESULTS

The electrically evoked auditory brainstem response thresholds were approximately one to two orders of magnitude lower than those evoked with conventional cochlear implants. We were able to close the cochleostomy, bring the cat into normal anatomical position, and obtain stable electrically evoked auditory brainstem responses for up to 52 hours. Plain film and computed tomographic studies indicated that the Utah Electrode Array neuroprosthesis was in the intended position in the nerve. Histological studies did not reveal hemorrhage or significant damage to the nerve.

CONCLUSION

Because the presented stimulation paradigm appears to significantly mitigate some of the problems of conventional cochlear implants, it may offer a new therapeutic approach to profound deafness.

Cochlear implants in young children

The past 20 years have seen the cochlear implant evolve from an innovative but radical concept to the standard of care in the management of children with severe to profound hearing loss. All children receiving the cochlear implant achieve substantial benefit; however, performance gains are optimized by a team approach to the evaluation and management of these children. The critical elements of this team include audiologists, speech pathologists, and surgeons with specific interest, expertise, and dedication to the management of children with cochlear implants. Children are not well served by practitioners who delegate follow-up to educational programs not experienced in children with implants. Long-term involvement and dedication on the part of teachers, speech pathologists, audiologists, surgeons, and family are critical to maximizing the benefit the child receives.