Auditory performance of children with cochlear ossification and partial implant insertion.

The management of the profoundly deaf child with a cochlear implant poses a special challenge, particularly when total ossification of the cochlea is present. In this setting, insertion of an electrode array into a child's cochlea is often difficult. Our experience supports the feasibility of partial insertion of a multichannel implant into the basal turn of an ossified cochlea. Five children with ossified cochleae who had undergone partial implantation of a multichannel electrode were compared with the performance of matched controls who had full insertion of multichannel implants. No dramatic differences were detected during a 6- to 18-month follow-up period on selected test measures. These preliminary results suggest that active electrode number may exert a limited effect on performance with a cochlear implant. Drilling out the basal turn of an ossified cochlea in conjunction with partial insertion of a multichannel implant appears to be an acceptable surgical and rehabilitational alternative for placement of a cochlear implant prosthesis in children with complete cochlear ossification.     

Aided auditory thresholds in children with postmeningitic deafness

Postmeningitic hearing loss is often bilateral, profound, and rapid in onset. Children with postmeningitic hearing loss may be identified as potential candidates for cochlear implantation. The length of time required for a definitive trial with conventional amplification, which must precede a final decision regarding cochlear implant surgery, has been the subject of debate. Twenty-five children with bilateral severe-to-profound postmeningitic sensorineural hearing loss were fitted with appropriate amplification and results of serial-aided tests were analyzed to determine the degree of benefit and changes in aided thresholds over time. Twelve children gave aided responses that clearly indicated the presence of residual hearing and good aided benefit. Ten youngsters have responded consistently in the vibrotactile range when aided, thus receiving limited benefit from conventional amplification. Of particular interest are three children who initially exhibited limited or no auditory responses but who, after a period of 16 to 25 months, showed excellent benefit with binaural hearing aids. These children are all in total communication programs and have received good auditory training. Caution should be exercised when concluding that such a child does not benefit from amplification.     

Sudden deafness: long‐term follow‐up and recurrence

We examined the long‐term outcome for patients with idiopathic sudden sensorineural hearing loss (sudden deafness), including the incidence of recurrence of sudden deafness. The subjects were 1798 individuals who came to Nagoya University hospital within 2 weeks of the onset of unilateral sudden deafness. Only 14 of the patients had a history of being diagnosed with sudden deafness. After their visit to our hospital, one patient had a recurrence in the ipsilateral ear and four patients experienced sudden deafness in the contralateral ear. We performed hearing examinations on 88 patients who revisited our hospital more than 10 years after unilateral sudden deafness. Of these patients, there was one with a recurrence in the ipsilateral ear and one with sudden deafness in the contralateral ear. Thus, in this series the recurrence of sudden deafness was rare.     

Potential insertion complications with cochlear implant electrodes

Objectives: The aim of this discussion paper and literature review was to estimate the incidence of a variety of complications associated with the surgical placement of cochlear implant (CI) electrode arrays and to discuss the implications and management of sub-optimal electrode placement.

Results: A review of the peer-reviewed literature suggests that the incidence of incomplete electrode insertion and kinking is more prevalent in straight arrays and not more than about 2% in CI recipients with normal cochlear anatomy/patency. Incidence of tip fold-over is greater with perimodiolar arrays but also occurs with straight arrays and is typically less than 5%. Conversely, electrode migration is more common with straight arrays, and high rates (up to 46%) have been reported in some studies. Scalar translocations have also been reported for both perimodiolar and straight arrays. Higher rates have been reported for stylet-based perimodiolar electrodes inserted via cochleostomy (up to 56%), but with much lower rates (<10%) with both sheath-based perimodiolar arrays and lateral wall arrays.

Electrode positioning complications represent a significant proportion of perioperative CI complications and compromise the level of benefit from the device. Careful surgical planning and appropriate pre- and intraoperative imaging can reduce the likelihood and impact of electrode positioning complications. There is also evidence that newer array designs are less prone to certain complications, particularly scalar translocation.

Conclusions: It is important that implanting surgeons are aware of the impact of sub-optimal electrode placement and the steps that can be taken to avoid, identify and manage such complications.     

Rapidly progressive bilateral postmeningitic deafness in children: Diagnosis and management

ObjectivesTo determine the diagnostic approach to severe or profound bilateral postmeningitic deafness and to propose management guidelines.Material and methodsA retrospective review of five patients (two adolescents and three infants) with rapidly progressive severe bilateral deafness following an episode of meningitis managed between 2004 and 2010.ResultsThe two adolescents presented Neisseria meningitidis meningitis and the three infants presented Streptococcus pneumoniae meningitis. Acquired bilateral deafness was diagnosed by audiometry an average of 68.8 days (range: 9–210) after the episode of meningitis. Behavioural audiological testing, adapted to age and state of health, was performed in all patients. Deafness was confirmed by Auditory Brainstem Response tests. All five patients were assessed by computed tomography (CT) and magnetic resonance imaging (MRI) within ten days. T2-weighted MRI sequences showed endolymph changes in four patients. CT scan demonstrated ossification in only one patient. Bilateral cochlear implant was performed in all patients, with complete electrode array insertion for eight implants and partial insertion for two implants (20 and 21 out of 22 electrodes inserted). Good results were obtained with cochlear implants in four cases.ConclusionsBilateral deafness can occur immediately or several months after bacterial meningitis, regardless of the micro-organism responsible, justifying screening by behavioural audiological testing adapted to age for two years following bacterial meningitis. Auditory Brainstem Response testing can confirm audiometric findings. When severe or profound bilateral deafness is observed, MRI must be performed urgently to detect endolymph inflammation or ossification. Early bilateral cochlear implantation is recommended in the presence of ossification.     

Integrity of the auditory pathway in young children with congenital and postmeningitic deafness

This study compares the functional integrity of the auditory pathways of congenitally deaf and postmeningitically deaf children. We used the electrical auditory brain stem response evoked by promontory stimulation to assess 49 profoundly deaf children before cochlear implantation. The age at implantation ranged from 21 months to 15 years (mean 4.5 years). The onset of deafness was either congenital or up to the age of 2 years (mean 5 months). The cause of deafness was meningitis in 19 children (39%) and congenital in 30 (61%). The number of children with identifiable waveform components (eV, eIII, and eII) was significantly greater in the congenitally deaf group. We also analyzed the amplitudes, the latencies, and 4 parameters of the amplitude input-output functions. All the statistically significant differences were in favor of better responses in the congenitally deaf children. These results suggest that the functional status of the peripheral neurons of the auditory pathways may be more intact in congenitally deaf children than in postmeningitic children.     

The multi-channel cochlear implant and the relief of severe-to-profound deafness

This personal reflection outlines the discoveries at the University of Melbourne leading to the multi-channel cochlear implant, and its development industrially by Cochlear Limited. My earlier experimental electrophysiological research demonstrated temporal coding occurred for only low frequencies, i.e. below 200-500 pulses/second. I was able to confirm these findings perceptually in behaviourally conditioned animals. In addition, these studies showed that temporal discrimination occurred across spatial coding channels. These experimental results correlated with the later conscious experience for electrical stimulation in my implant patients. In addition, the mid-to-high frequencies were coded in part by place of stimulation using bipolar and monopolar stimulation to restrict current spread. Furthermore, place of stimulation had the qualities of sharpness and dullness, and was also experienced as vowels. Owing to the limitation in coding speech with a physiological model due to the overlap of electrical current leading to unpredictable variations in loudness, a speech coding strategy that extracted the most important speech features for transmission through an electro-neural 'bottle-neck' to the brain was explored. Our inaugural strategy, discovered in 1978, extracted the second formant for place of stimulation, voicing for rate of stimulation, and sound pressure for current level. This was the first coding strategy to provide open-set speech understanding, as shown by standard audiological tests, and it became the first clinically successful interface between the world and human consciousness. This strategy was improved with place coding for the third formant or high-frequency spectrum, and then the spectral maxima. In 1989, I operated on our first patient to receive a bilateral implant, and in 1990, the first with a bimodal processor. The psychophysics and speech perception for these showed that the stimuli from each side could be fused into a single image, and localized according to differences in intensity and time of arrival of the stimuli. There were significant improvements for speech perception in noise. In 1985, I implanted our first children with the multi-channel prosthesis and found that speech understanding and spoken language were greatly improved the younger the child at surgery, and especially when younger than 12 months. Speech understanding was strongly related to the development of place coding. In 1990, the US Food and Drug Administration approved the implant for deaf children, the first by any world health regulatory body making it the first major advance in helping deaf children to communicate.     

The multi-channel cochlear implant and the relief of severe-to-profound deafness

Abstract

This personal reflection outlines the discoveries at the University of Melbourne leading to the multi-channel cochlear implant, and its development industrially by Cochlear Limited. My earlier experimental electrophysiological research demonstrated temporal coding occurred for only low frequencies, i.e. below 200–500 pulses/second. I was able to confirm these findings perceptually in behaviourally conditioned animals. In addition, these studies showed that temporal discrimination occurred across spatial coding channels. These experimental results correlated with the later conscious experience for electrical stimulation in my implant patients. In addition, the mid-to-high frequencies were coded in part by place of stimulation using bipolar and monopolar stimulation to restrict current spread. Furthermore, place of stimulation had the qualities of sharpness and dullness, and was also experienced as vowels. Owing to the limitation in coding speech with a physiological model due to the overlap of electrical current leading to unpredictable variations in loudness, a speech coding strategy that extracted the most important speech features for transmission through an electro-neural ‘bottle-neck’ to the brain was explored. Our inaugural strategy, discovered in 1978, extracted the second formant for place of stimulation, voicing for rate of stimulation, and sound pressure for current level. This was the first coding strategy to provide open-set speech understanding, as shown by standard audiological tests, and it became the first clinically successful interface between the world and human consciousness. This strategy was improved with place coding for the third formant or high-frequency spectrum, and then the spectral maxima. In 1989, I operated on our first patient to receive a bilateral implant, and in 1990, the first with a bimodal processor. The psychophysics and speech perception for these showed that the stimuli from each side could be fused into a single image, and localized according to differences in intensity and time of arrival of the stimuli. There were significant improvements for speech perception in noise. In 1985, I implanted our first children with the multi-channel prosthesis and found that speech understanding and spoken language were greatly improved the younger the child at surgery, and especially when younger than 12 months. Speech understanding was strongly related to the development of place coding. In 1990, the US Food and Drug Administration approved the implant for deaf children, the first by any world health regulatory body making it the first major advance in helping deaf children to communicate.     

Auditory responses in cochlear implant users with and without GJB2 deafness

OBJECTIVE/HYPOTHESIS: It is reasonable to suppose that the pattern of sensorineural damage along the length of the cochlea depends on the etiology of a hearing loss (HL). In GJB2-related deafness, we hypothesize that gap junction deficits are uniformly distributed and will result in similar damage along the length of the cochlea as compared with non-GJB2 subjects. We assessed this by measuring patterns of neural activity and hearing from apical versus basal cochlear implant electrode regions. STUDY DESIGN: This was a prospective, blind, controlled study. METHODS: Blood from 301 pediatric cochlear implant users was analyzed for mutations in GJB2 by direct sequencing. After exclusion of patients with monoallelic GJB2 mutations, associated syndromes, or risk factors for HL that were not congenital, 39 children with biallelic GJB2 mutations and 58 without GJB2 mutations were evaluated. Hearing was measured before implantation at frequencies ranging from 250 Hz to 8 kHz. After implantation, neural activity at the apical and basal ends of the implanted array was measured using electrically evoked compound action potentials of the auditory nerve (ECAPs) and evoked stapedius reflexes (ESRs). RESULTS: GJB2 and non-GJB2 groups were not significantly different with respect to sex, age at implantation, duration of auditory deprivation, hearing aid use, duration of aided hearing, ear implanted, implant model, or depth of insertion (P>.05). Children with GJB2-related HL had greater similarities between low- and high-frequency residual hearing and between neural activity electrically evoked at apical and basal regions of the cochlea as compared with children with non-GJB2-related HL who demonstrated larger deficits in basal regions. CONCLUSION: Results suggest more consistent spiral ganglion survival along the length of the cochlea in GJB2-related HL as compared with non-GJB2-related HL, which appears to involve a decreasing gradient of spiral ganglion survival from the apex to the base of the cochlea. Our findings support our premise that in GJB2-related HL, dysfunction of gap junctions likely occurs to a similar degree in the apical and basal regions of the cochlea. This knowledge might be used to customize implantable devices for patients with HL in the future.     

The long‐term effect of unilateral t‐tube insertion in patients undergoing cleft palate repair: 20‐year follow‐up of a randomised controlled trial

Objectives: Between July 1984 and March 1987, all children that underwent repair for primary cleft palate at the Queen Victoria Hospital were enrolled in a clinical trial. Those found to have otitis media with effusion at time of surgery had a t‐tube inserted into one randomised ear, whilst the other ear received no treatment. The object of the study was to reassess the patients from the original trial to discover the impact of the unilateral t‐tube, twenty years later analysed on an intention to treat basis. Design: Children that underwent primary palatal closure during the study dates were identified from the cleft palate database. Patients that were involved in the original trial were identified, contacted and invited to take part in the follow‐up study. Setting: Tertiary referral Specialist unit. Participants: Twenty‐two patients were identified as potential study participants. Of this group, fourteen were contactable and seven participants agreed to take part in our follow‐up study. Main outcome measures: Persistent symptomatology, otoscopy, pure tone audiometry and tympanometry. Results: Follow‐up results were compared within the original treatment groups from the primary study, on an intention to treat basis. Otoscopically the ears were normal in 2 of the 7 treated ears compared with four of the seven non‐treated ears. All the other ear ears had various types of chronic otitis media. Four of the seven had hearing of >10 dB in the treated ear compared with the non‐treated ear. Conclusions: These findings would indicate need for caution in the use of t‐tubes in the cleft population and raises the question of long‐term follow‐up to assess for secondary cholesteatoma.