A cochlear implant device is normally inserted into the scala tympani via a posterior tympanotomy... more A cochlear implant device is normally inserted into the scala tympani via a posterior tympanotomy and cochleostomy. There has been no previous report of displacement of the array into the vestibular part of the labyrinth. The authors present and discuss the audiological and electrophysiological measurements of a case in which part of the array herniated through into the vestibule.
To describe an atypical waveform, termed an abnormal positive potential (APP), on round window el... more To describe an atypical waveform, termed an abnormal positive potential (APP), on round window electrocochleograms (RW ECochG) of children and to relate its occurrence to clinical history. APPs were identified prospectively, and a retrospective analysis was made of these patients' clinical histories, audiograms, and auditory outcomes (hearing aid, cochlear implant, or nonauditory communication) Tertiary referral teaching hospital, day surgery and clinics. All 431 children <110 months of age suspected of a severe to profound hearing loss who underwent RW ECochG from January 1993 to August 1997. Diagnostic RW ECochG for auditory threshold estimation. The presence on the RW ECochG of the APP: an early positive potential in the absence of a compound action potential (CAP). An APP was observed in 34 children. The APP was most marked in response to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hearing loss. The brainstem evoked potential of these children showed an...
Aim: This study aims at evaluating the functional consequences of long-term high-frequency deafne... more Aim: This study aims at evaluating the functional consequences of long-term high-frequency deafness, on the ability to process low-frequency speech sounds, in partially deaf patients. Material and Methods: 22 hearing-impaired subjects participated to this study, all had hearing thresholds superior to 90 dB HL at 1000 Hz and above. Stimuli, administered at the most comfortable intensity level, were speech signals unfiltered or low-pass filtered at various cut-off frequencies, every 1 / 2 -octave between 250 and 2000 Hz. Results: Results show a significant positive correlation between speech recognition scores and deafness duration. The strongest predictor of performance was the relative hearing-loss duration, expressed as the ratio of deafness duration divided by patient's age. Conclusions: Following a long-standing high-frequency deafferentation, patients may have learned to only rely on lowfrequency information to understand, in such a way that they "ignore" high-frequency information.
... Gardner-Berry, Kirsty; Gibson, William P.; Sanli, Halit. ... Author Information. Kirsty Gardn... more ... Gardner-Berry, Kirsty; Gibson, William P.; Sanli, Halit. ... Author Information. Kirsty Gardner-Berry, MA, is a Diagnostic and Research Audiologist; William P. Gibson, MD, is Professor and Director; and Halit Sanli, PhD, is a Biomedical Engineer, all at Sydney Cochlear Implant Centre. ...
Neuropathies of the Auditory and Vestibular Eighth Cranial Nerves, 2009
ABSTRACT Currently, the physiological mechanisms underlying auditory neuropathy are unclear, and ... more ABSTRACT Currently, the physiological mechanisms underlying auditory neuropathy are unclear, and there are likely to be multiple sites of lesion. A better understanding of the disruption in individual cases may lead to more effective management and device selection. Frequency-specifi c round-window electrocochleography (ECochG) waveforms were used to assess local hair cell, dendritic, and axonal currents generated within the cochlea in 15 subjects with auditory neuropathy (16 ears). These results were compared with electrically evoked auditory brainstem response (EABR) measured after cochlear implantation. The results of this study demonstrate that predominantly two patterns of ECochG waveforms can be identifi ed: (i) a prolonged latency of the hair cell summating potential (SP) waveform with or without residual CAP activity and (ii) a normal latency SP, typically followed by a dendritic potential (DP). We show that seven of eight subjects with a prolonged SP showed a normal EABR waveform, consistent with a presynaptic lesion, whereas six of seven subjects with a normal latency SP showed poor morphology or absent EABR waveforms, consistent with a postsynaptic lesion. We suggest that a presynaptic and postsynaptic type of auditory neuropathy exist, which may have implications for the fi tting of cochlear implants.
To compare mean impedance levels, neural response telemetry (NRT), and auditory perception after ... more To compare mean impedance levels, neural response telemetry (NRT), and auditory perception after initial and explant-reimplant pediatric cochlear implants. Retrospective case review. Tertiary referral hospital and cochlear implant program. Children 0 to 16 years inclusive who have undergone explant-reimplant of their cochlear implant. Impedance levels, NRT, and speech perception performance. Impedance, NRT, and auditory perception at switch on, 3 months, 12 months, 3 years, and 5 years after initial cochlear implant and reimplantation. The explant-reimplant group receiving Cochlear contour array had significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) raised impedance at switch on, 3 months, 12 months, and 3 years, compared with their initial implant. The explant-reimplant group receiving Cochlear straight array had marginally significant (p = 0.045) raised impedance at switch on, 3 months, 12 months, and 3 and 5 years. Infection was associated with greater increases in impedance in the reimplant Contour group. NRT was increased in the explant-reimplant group but not significantly (p = 0.06). Auditory perception returned to preexplant levels within 6 months in 61% of children. Impedance is higher after explant-reimplant and remains increased for years after explant-reimplant with Cochlear contour and to a lesser degree the straight array device.
To examine the outcome of cochlear implantation in children with auditory neuropathy (AN) and coc... more To examine the outcome of cochlear implantation in children with auditory neuropathy (AN) and cochlear nerve deficiency (Group A). Results are compared with a cohort of children with AN and normal cochlear nerves (Group B). Retrospective cohort study. The Sydney Cochlear Implant Centre and the Children&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Hospital at Westmead. Children younger than 15 years with bilateral profound sensorineural hearing loss and the diagnosis of AN confirmed on electrophysiologic testing. All children underwent cochlear implantation with Nucleus 24 cochlear implants from 1997 to 2006. Magnetic resonance imaging was examined for deficiency of the vestibulocochlear nerve. Brain and inner ear abnormalities were recorded. Cochlear implant outcomes and demographic variables were compared. Melbourne speech perception score (MSPS) at 1 year and implant evoked electric auditory brainstem response (EABR). Group A performed significantly worse on both parameters than Group B. In Group A, median MSPS was 1, compared with a median score of 4 in Group B (z = -3.010; p = 0.003). EABR was abnormal in 13 of 15 (87%) children in Group A, compared with 9 of 39 (23%) in Group B. Children in both groups with abnormal EABR had significantly worse MSPS (z = -2.780; p = 0.005). Fourteen of 15 children with cochlear nerve deficiency had associated inner ear abnormalities. Children with AN can have associated cochlear nerve deficiency. These patients have worse speech perception scores at 1 year post cochlear implantation, higher rates of abnormal EABR, and more associated inner ear abnormalities than children with AN and normal cochlear nerves.
The physiological mechanisms underlying auditory neuropathy (AN) remain unclear and it is likely ... more The physiological mechanisms underlying auditory neuropathy (AN) remain unclear and it is likely that the multiple disruptions are classified under the broadly defined term. Cochlear implantation is being more widely used in this population to bypass the suspected site-of-lesion although a number of cases have been identified within the Sydney Cochlear Implant Centre where this management strategy has been unsuccessful. It is likely that this relates to the different physiological mechanisms underlying AN. To investigate the site-of-lesion in AN, frequency-specific round window electrocochleography (ECochG) was used to assess local hair-cell, dendritic, and axonal currents generated within the cochlea in 14 subjects with AN and compared with responses from two normally hearing subjects. ECochG results were then compared with electrically evoked auditory brain stem response (EABR) measured after cochlear implantation. The results of this study demonstrate that two dominant patterns of ECochG waveforms (produced by a high-frequency alternating tone burst) can be identified in this population of AN subjects: (a) gross waveform showing a prolonged summating potential (SP) latency that, in most cases, is followed by a small compound action potential; and (b) gross waveform showing a normal latency SP waveform followed by a broad negative potential [assumed to reflect the dendritic potential (DP) identified in anaesthetized guinea-pigs]. This study demonstrates that in most subjects (n = 7) with a prolonged latency SP but no DP, normal morphology EABR waveforms were elicited for all electrode channels. On the other hand, all subjects (n = 7) who showed a normal latency SP followed by a broad negative DP, showed EABR waveforms that were absent or having poor wave V morphology. The authors&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; interpretation of this is that ECochG results may provide a classification of AN into pre- and postsynaptic lesions. We suggest that a presynaptic and postsynaptic type of AN exist that may have implications for the fitting of cochlear implants.
To describe the round window electrocochleography (RWECochG) and electric auditory brainstem resp... more To describe the round window electrocochleography (RWECochG) and electric auditory brainstem responses (EABR) in ears affected by auditory neuropathy (AN), and to determine if these electrophysiological tests can predict the outcome following cochlear implant surgery. A longitudinal study of all pediatric cochlear implant patients between 1994 and 2005 was undertaken. Speech perception outcomes after cochlear implantation and electrophysiological data were collected prospectively and analyzed. Some otoacoustic emissions (OAE) data were collected retrospectively during the neonatal period. All subjects were tested using round window electrocochleography (RWEcochG), auditory brainstem responses (ABR), and implant-evoked electric auditory brainstem responses (EABR). The auditory neuropathy (AN) group consisted of 39 children (78 ears) which had present OAE and absent or grossly abnormal ABR (a broad N1 component only). All 78 ears from the 39 AN children showed large cochlear microphonics (CM) and an abnormal positive potential (APP) using RW ECochG. A further 21 children showed large CM and APP but had not been tested for OAE. In total, 60 children were discovered to have APP among 435 pediatric patients who received a cochlear implant. Electrically evoked ABR (EABR) from the implanted ear were normal in 45 and abnormal in 15. 46 age matched patients without large CM and APP were used as a control group. Two year postimplant scores (Melbourne categories) were: 6.27 (APP and normal EABR), 2.25 (APP and abnormal EABR) and 5.37 (control group). Mann-Whitney U Test for nonparametric data was used to test for significant difference at significance level p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.005 (two tailed). The APP ears which provided normal EABR had significantly better outcomes after cochlear implantation than APP ears which had abnormal EABR. Furthermore, the APP ears which provided normal EABR performed significantly better after cochlear implant surgery than the control group of patients with no OAE, appropriate ABR results and normal EABR. Ears affected by AN provide large CM and APP on RW ECochG. The presence of normal EABR may indicate a significantly better outcome after cochlear implant surgery than for those APP ears which had abnormal or absent EABR. Based on these findings it is suggested that the presence of APP and/ or OAE in 75% of the ears which have absent or abnormal ABR may not indicate a pathological condition affecting the auditory nerve or synapse but only survival of outer hair cells despite extensive loss of inner hair cells.
Electrically evoked auditory brainstem responses (EABR) were obtained intra-operatively from chil... more Electrically evoked auditory brainstem responses (EABR) were obtained intra-operatively from children receiving full insertion of Cochlear CI24 implant. The EABR waveform was quantifi ed according to the presence or absence of waves (eII-eV). Each trace was scored from 0-3 providing a maximum score for all 22 electrodes of 66 in the monopolar mode. Speech perception scores were measured after one year in 245 children and after two years of cochlear implant use in 148 children. Signifi cant differences in the EABR waveforms were found between those recipients who achieved scores of 4 or greater on the Melbourne scale and those recipients who only had a modest outcome. After two years, the outcome showed even greater differences. The group of 103 children who had outcomes of 4 or greater at one year improved from a mean score of 4.7 to 5.7. The group of 45 children who had outcomes of 3 or less at one year only improved from a mean score of 2.9 to 3.15. In this latter group, only four children showed any signifi cant improvement.
agreement on the exact positioning of the stimulating electrode on the medial wall of the mesotym... more agreement on the exact positioning of the stimulating electrode on the medial wall of the mesotympanum. The authors investigate the relationship of the positioning of the electrode and the brainstem response.
Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause prof... more Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause profound hearing loss and labyrinthitis ossifi cans. We obtained data from the New South Wales health department for cases of meningitis between 1995 and 2005 (1568 cases) and the Sydney Cochlear Implant Centre for cochlear implant patients with hearing loss secondary to meningitis from 1984 to 2005 (70 ears in 59 patients). The aetiological agents were compared with regard to their ability to cause profound hearing loss and cochlear ossifi cation. Neisseria meningitidis resulted in 56.9% of cases of meningitis and 11.4% of the cases of profound hearing loss resulting in cochlear implantation (incidence of profound hearing loss of 0.4%). Streptococcus pneumoniae, however, caused 41.1% of meningitis but 85.7% of cochlear implantation (incidence of 4.6%). Labyrinthitis ossifi cans was more common after infection with Streptococcus pneumoniae but there was no statistically signifi cant difference between Streptococcus pneumoniae, Haemophilus infl uenzae or Neisseria meningitidis for labyrinthitis ossifi cans (p = 0.45, chi-squared test). In conclusion Neisseria meningitidis meningitis carries a very low risk of profound hearing loss but Streptococcus pneumoniae meningitis a signifi cantly higher risk.
Objectives To list the complications encountered in a series of 844 consecutive patients and to e... more Objectives To list the complications encountered in a series of 844 consecutive patients and to evaluate the long-term difference in wound and flap problems between large and small incisions. Patients 844 consecutive patients underwent cochlear implantation at the Sydney Cochlear Implant Centre. 212 cases were operated on prior to October 1994 using the retroauricular 'C'-shaped incision or a postauricular incision with a horizontal posterior limb. After October 1994 a new, small vertical postaural incision was used in all patients. Postoperative problems were analysed. Study design Prospective longitudinal study of cochlear implant recipients from1984 to 2003. Setting Te rtiary care referral centre. Intervention Change in incision for cochlear implantation. Main outcome measure Causes of postoperative problems, need for reimplatation, and wound and flap problems. Results 80 out of the total 844 patients underwent revision procedures for various reasons. The commonest cause of reimplantation was device failure (2.01%) or suboptimum performance of the device (2.37%). Wound and flap problems were encountered by 5 patients out of 212 (2.3%) in the first group. In comparison, 7 out of 632 patients (1.10%) from the later group experienced wound and flap problems using the new incision.
To assess the feasibility of intra-operative monitoring of residual hearing using electrocochleog... more To assess the feasibility of intra-operative monitoring of residual hearing using electrocochleography (ECOG) during cochlear implantation. We present our methods and preliminary results. We attempted to monitor 21 consecutive paediatric and adult subjects during cochlear implantation. All subjects were implanted via a promontory cochleostomy with full electrode insertions of Cochlear(TM) Nucleus® (Cochlear Nucleus, Cochlear Ltd, Australia) devices: 8 with straight electrodes and 13 with contoured electrodes. Baseline recordings were made after the completion of the posterior tympanotomy, and subsequently at stages of the cochleostomy and electrode insertion. We were unable to obtain recordings on five patients because the ear-insert tubing kinked, which disrupted transmission of the stimulus. Five had insufficient cochlear function to be able to record a baseline ECOG. No subjects in whom we were able to obtain a satisfactory baseline ECOG (n=11) had a reduction in ECOG action potential (AP) amplitude, morphology or threshold up to completion of the cochleostomy. Seven maintained an unchanged ECOG throughout the procedure to full insertion. An implant had to be replaced because of a faulty straight electrode in one patient. The amplitude significantly reduced during insertion of the replacement array. Two had a reduction in amplitude, threshold, and shape of the wave related to inadvertent suction of the perilymph. Subsequently, one maintained this changed ECOG to the end of the procedure, but the other progressed to complete loss of the ECOG during insertion of the array. One other subject had a significant reduction in the amplitude during insertion of the electrode from a depth of approximately 18mm to full insertion. Intra-operative monitoring of residual hearing may be possible in most patients undergoing cochlear implantation. This pilot study suggests that cochleostomy is not associated with intra-operative loss of residual hearing; ECOG can be preserved during the procedure in most patients; intra-operative loss of hearing is most likely to occur when the tip of the array reaches the basal turn of the cochlea. This risk may increase if the array has to be removed and re-inserted. Suction of perilymph causes immediate changes, which may not recover.
Waardenburg syndrome presents with dystopia canthorum, pigmentary abnormalities of hair, iris and... more Waardenburg syndrome presents with dystopia canthorum, pigmentary abnormalities of hair, iris and skin (often a white forelock and heterochromia iridis) and sensorineural deafness. The authors review the electrophysiological and psychophysical findings of implanted children with Waardenburg syndrome at the Sydney Cochlear Implant Centre. Twenty children with Waardenburg syndrome received cochlear implants between 1985 and 2001. Electrical auditory brainstem response (EABR) was performed in all of these patients intra-operatively as part of the routine investigations. Only 13 of these patients were assessed one year or more post-operatively by means of the Melbourne Categories (0-7). Four patients (20%) were found to have abnormal EABR recordings. The mode of Melbourne Categories in this group (n = 3) was 1 at one year post-operation. The other 16 patients were found to have normal EABR and the mode of Melbourne Categories in this group (n = 10) was 7. A poor outcome after cochlear implantation was associated with abnormal EABR recordings (a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;true&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; auditory neuropathy) and was found in a significant proportion of patients with Waardenburg syndrome.
A cochlear implant device is normally inserted into the scala tympani via a posterior tympanotomy... more A cochlear implant device is normally inserted into the scala tympani via a posterior tympanotomy and cochleostomy. There has been no previous report of displacement of the array into the vestibular part of the labyrinth. The authors present and discuss the audiological and electrophysiological measurements of a case in which part of the array herniated through into the vestibule.
To describe an atypical waveform, termed an abnormal positive potential (APP), on round window el... more To describe an atypical waveform, termed an abnormal positive potential (APP), on round window electrocochleograms (RW ECochG) of children and to relate its occurrence to clinical history. APPs were identified prospectively, and a retrospective analysis was made of these patients' clinical histories, audiograms, and auditory outcomes (hearing aid, cochlear implant, or nonauditory communication) Tertiary referral teaching hospital, day surgery and clinics. All 431 children <110 months of age suspected of a severe to profound hearing loss who underwent RW ECochG from January 1993 to August 1997. Diagnostic RW ECochG for auditory threshold estimation. The presence on the RW ECochG of the APP: an early positive potential in the absence of a compound action potential (CAP). An APP was observed in 34 children. The APP was most marked in response to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hearing loss. The brainstem evoked potential of these children showed an...
Aim: This study aims at evaluating the functional consequences of long-term high-frequency deafne... more Aim: This study aims at evaluating the functional consequences of long-term high-frequency deafness, on the ability to process low-frequency speech sounds, in partially deaf patients. Material and Methods: 22 hearing-impaired subjects participated to this study, all had hearing thresholds superior to 90 dB HL at 1000 Hz and above. Stimuli, administered at the most comfortable intensity level, were speech signals unfiltered or low-pass filtered at various cut-off frequencies, every 1 / 2 -octave between 250 and 2000 Hz. Results: Results show a significant positive correlation between speech recognition scores and deafness duration. The strongest predictor of performance was the relative hearing-loss duration, expressed as the ratio of deafness duration divided by patient's age. Conclusions: Following a long-standing high-frequency deafferentation, patients may have learned to only rely on lowfrequency information to understand, in such a way that they "ignore" high-frequency information.
... Gardner-Berry, Kirsty; Gibson, William P.; Sanli, Halit. ... Author Information. Kirsty Gardn... more ... Gardner-Berry, Kirsty; Gibson, William P.; Sanli, Halit. ... Author Information. Kirsty Gardner-Berry, MA, is a Diagnostic and Research Audiologist; William P. Gibson, MD, is Professor and Director; and Halit Sanli, PhD, is a Biomedical Engineer, all at Sydney Cochlear Implant Centre. ...
Neuropathies of the Auditory and Vestibular Eighth Cranial Nerves, 2009
ABSTRACT Currently, the physiological mechanisms underlying auditory neuropathy are unclear, and ... more ABSTRACT Currently, the physiological mechanisms underlying auditory neuropathy are unclear, and there are likely to be multiple sites of lesion. A better understanding of the disruption in individual cases may lead to more effective management and device selection. Frequency-specifi c round-window electrocochleography (ECochG) waveforms were used to assess local hair cell, dendritic, and axonal currents generated within the cochlea in 15 subjects with auditory neuropathy (16 ears). These results were compared with electrically evoked auditory brainstem response (EABR) measured after cochlear implantation. The results of this study demonstrate that predominantly two patterns of ECochG waveforms can be identifi ed: (i) a prolonged latency of the hair cell summating potential (SP) waveform with or without residual CAP activity and (ii) a normal latency SP, typically followed by a dendritic potential (DP). We show that seven of eight subjects with a prolonged SP showed a normal EABR waveform, consistent with a presynaptic lesion, whereas six of seven subjects with a normal latency SP showed poor morphology or absent EABR waveforms, consistent with a postsynaptic lesion. We suggest that a presynaptic and postsynaptic type of auditory neuropathy exist, which may have implications for the fi tting of cochlear implants.
To compare mean impedance levels, neural response telemetry (NRT), and auditory perception after ... more To compare mean impedance levels, neural response telemetry (NRT), and auditory perception after initial and explant-reimplant pediatric cochlear implants. Retrospective case review. Tertiary referral hospital and cochlear implant program. Children 0 to 16 years inclusive who have undergone explant-reimplant of their cochlear implant. Impedance levels, NRT, and speech perception performance. Impedance, NRT, and auditory perception at switch on, 3 months, 12 months, 3 years, and 5 years after initial cochlear implant and reimplantation. The explant-reimplant group receiving Cochlear contour array had significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) raised impedance at switch on, 3 months, 12 months, and 3 years, compared with their initial implant. The explant-reimplant group receiving Cochlear straight array had marginally significant (p = 0.045) raised impedance at switch on, 3 months, 12 months, and 3 and 5 years. Infection was associated with greater increases in impedance in the reimplant Contour group. NRT was increased in the explant-reimplant group but not significantly (p = 0.06). Auditory perception returned to preexplant levels within 6 months in 61% of children. Impedance is higher after explant-reimplant and remains increased for years after explant-reimplant with Cochlear contour and to a lesser degree the straight array device.
To examine the outcome of cochlear implantation in children with auditory neuropathy (AN) and coc... more To examine the outcome of cochlear implantation in children with auditory neuropathy (AN) and cochlear nerve deficiency (Group A). Results are compared with a cohort of children with AN and normal cochlear nerves (Group B). Retrospective cohort study. The Sydney Cochlear Implant Centre and the Children&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Hospital at Westmead. Children younger than 15 years with bilateral profound sensorineural hearing loss and the diagnosis of AN confirmed on electrophysiologic testing. All children underwent cochlear implantation with Nucleus 24 cochlear implants from 1997 to 2006. Magnetic resonance imaging was examined for deficiency of the vestibulocochlear nerve. Brain and inner ear abnormalities were recorded. Cochlear implant outcomes and demographic variables were compared. Melbourne speech perception score (MSPS) at 1 year and implant evoked electric auditory brainstem response (EABR). Group A performed significantly worse on both parameters than Group B. In Group A, median MSPS was 1, compared with a median score of 4 in Group B (z = -3.010; p = 0.003). EABR was abnormal in 13 of 15 (87%) children in Group A, compared with 9 of 39 (23%) in Group B. Children in both groups with abnormal EABR had significantly worse MSPS (z = -2.780; p = 0.005). Fourteen of 15 children with cochlear nerve deficiency had associated inner ear abnormalities. Children with AN can have associated cochlear nerve deficiency. These patients have worse speech perception scores at 1 year post cochlear implantation, higher rates of abnormal EABR, and more associated inner ear abnormalities than children with AN and normal cochlear nerves.
The physiological mechanisms underlying auditory neuropathy (AN) remain unclear and it is likely ... more The physiological mechanisms underlying auditory neuropathy (AN) remain unclear and it is likely that the multiple disruptions are classified under the broadly defined term. Cochlear implantation is being more widely used in this population to bypass the suspected site-of-lesion although a number of cases have been identified within the Sydney Cochlear Implant Centre where this management strategy has been unsuccessful. It is likely that this relates to the different physiological mechanisms underlying AN. To investigate the site-of-lesion in AN, frequency-specific round window electrocochleography (ECochG) was used to assess local hair-cell, dendritic, and axonal currents generated within the cochlea in 14 subjects with AN and compared with responses from two normally hearing subjects. ECochG results were then compared with electrically evoked auditory brain stem response (EABR) measured after cochlear implantation. The results of this study demonstrate that two dominant patterns of ECochG waveforms (produced by a high-frequency alternating tone burst) can be identified in this population of AN subjects: (a) gross waveform showing a prolonged summating potential (SP) latency that, in most cases, is followed by a small compound action potential; and (b) gross waveform showing a normal latency SP waveform followed by a broad negative potential [assumed to reflect the dendritic potential (DP) identified in anaesthetized guinea-pigs]. This study demonstrates that in most subjects (n = 7) with a prolonged latency SP but no DP, normal morphology EABR waveforms were elicited for all electrode channels. On the other hand, all subjects (n = 7) who showed a normal latency SP followed by a broad negative DP, showed EABR waveforms that were absent or having poor wave V morphology. The authors&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; interpretation of this is that ECochG results may provide a classification of AN into pre- and postsynaptic lesions. We suggest that a presynaptic and postsynaptic type of AN exist that may have implications for the fitting of cochlear implants.
To describe the round window electrocochleography (RWECochG) and electric auditory brainstem resp... more To describe the round window electrocochleography (RWECochG) and electric auditory brainstem responses (EABR) in ears affected by auditory neuropathy (AN), and to determine if these electrophysiological tests can predict the outcome following cochlear implant surgery. A longitudinal study of all pediatric cochlear implant patients between 1994 and 2005 was undertaken. Speech perception outcomes after cochlear implantation and electrophysiological data were collected prospectively and analyzed. Some otoacoustic emissions (OAE) data were collected retrospectively during the neonatal period. All subjects were tested using round window electrocochleography (RWEcochG), auditory brainstem responses (ABR), and implant-evoked electric auditory brainstem responses (EABR). The auditory neuropathy (AN) group consisted of 39 children (78 ears) which had present OAE and absent or grossly abnormal ABR (a broad N1 component only). All 78 ears from the 39 AN children showed large cochlear microphonics (CM) and an abnormal positive potential (APP) using RW ECochG. A further 21 children showed large CM and APP but had not been tested for OAE. In total, 60 children were discovered to have APP among 435 pediatric patients who received a cochlear implant. Electrically evoked ABR (EABR) from the implanted ear were normal in 45 and abnormal in 15. 46 age matched patients without large CM and APP were used as a control group. Two year postimplant scores (Melbourne categories) were: 6.27 (APP and normal EABR), 2.25 (APP and abnormal EABR) and 5.37 (control group). Mann-Whitney U Test for nonparametric data was used to test for significant difference at significance level p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.005 (two tailed). The APP ears which provided normal EABR had significantly better outcomes after cochlear implantation than APP ears which had abnormal EABR. Furthermore, the APP ears which provided normal EABR performed significantly better after cochlear implant surgery than the control group of patients with no OAE, appropriate ABR results and normal EABR. Ears affected by AN provide large CM and APP on RW ECochG. The presence of normal EABR may indicate a significantly better outcome after cochlear implant surgery than for those APP ears which had abnormal or absent EABR. Based on these findings it is suggested that the presence of APP and/ or OAE in 75% of the ears which have absent or abnormal ABR may not indicate a pathological condition affecting the auditory nerve or synapse but only survival of outer hair cells despite extensive loss of inner hair cells.
Electrically evoked auditory brainstem responses (EABR) were obtained intra-operatively from chil... more Electrically evoked auditory brainstem responses (EABR) were obtained intra-operatively from children receiving full insertion of Cochlear CI24 implant. The EABR waveform was quantifi ed according to the presence or absence of waves (eII-eV). Each trace was scored from 0-3 providing a maximum score for all 22 electrodes of 66 in the monopolar mode. Speech perception scores were measured after one year in 245 children and after two years of cochlear implant use in 148 children. Signifi cant differences in the EABR waveforms were found between those recipients who achieved scores of 4 or greater on the Melbourne scale and those recipients who only had a modest outcome. After two years, the outcome showed even greater differences. The group of 103 children who had outcomes of 4 or greater at one year improved from a mean score of 4.7 to 5.7. The group of 45 children who had outcomes of 3 or less at one year only improved from a mean score of 2.9 to 3.15. In this latter group, only four children showed any signifi cant improvement.
agreement on the exact positioning of the stimulating electrode on the medial wall of the mesotym... more agreement on the exact positioning of the stimulating electrode on the medial wall of the mesotympanum. The authors investigate the relationship of the positioning of the electrode and the brainstem response.
Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause prof... more Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause profound hearing loss and labyrinthitis ossifi cans. We obtained data from the New South Wales health department for cases of meningitis between 1995 and 2005 (1568 cases) and the Sydney Cochlear Implant Centre for cochlear implant patients with hearing loss secondary to meningitis from 1984 to 2005 (70 ears in 59 patients). The aetiological agents were compared with regard to their ability to cause profound hearing loss and cochlear ossifi cation. Neisseria meningitidis resulted in 56.9% of cases of meningitis and 11.4% of the cases of profound hearing loss resulting in cochlear implantation (incidence of profound hearing loss of 0.4%). Streptococcus pneumoniae, however, caused 41.1% of meningitis but 85.7% of cochlear implantation (incidence of 4.6%). Labyrinthitis ossifi cans was more common after infection with Streptococcus pneumoniae but there was no statistically signifi cant difference between Streptococcus pneumoniae, Haemophilus infl uenzae or Neisseria meningitidis for labyrinthitis ossifi cans (p = 0.45, chi-squared test). In conclusion Neisseria meningitidis meningitis carries a very low risk of profound hearing loss but Streptococcus pneumoniae meningitis a signifi cantly higher risk.
Objectives To list the complications encountered in a series of 844 consecutive patients and to e... more Objectives To list the complications encountered in a series of 844 consecutive patients and to evaluate the long-term difference in wound and flap problems between large and small incisions. Patients 844 consecutive patients underwent cochlear implantation at the Sydney Cochlear Implant Centre. 212 cases were operated on prior to October 1994 using the retroauricular 'C'-shaped incision or a postauricular incision with a horizontal posterior limb. After October 1994 a new, small vertical postaural incision was used in all patients. Postoperative problems were analysed. Study design Prospective longitudinal study of cochlear implant recipients from1984 to 2003. Setting Te rtiary care referral centre. Intervention Change in incision for cochlear implantation. Main outcome measure Causes of postoperative problems, need for reimplatation, and wound and flap problems. Results 80 out of the total 844 patients underwent revision procedures for various reasons. The commonest cause of reimplantation was device failure (2.01%) or suboptimum performance of the device (2.37%). Wound and flap problems were encountered by 5 patients out of 212 (2.3%) in the first group. In comparison, 7 out of 632 patients (1.10%) from the later group experienced wound and flap problems using the new incision.
To assess the feasibility of intra-operative monitoring of residual hearing using electrocochleog... more To assess the feasibility of intra-operative monitoring of residual hearing using electrocochleography (ECOG) during cochlear implantation. We present our methods and preliminary results. We attempted to monitor 21 consecutive paediatric and adult subjects during cochlear implantation. All subjects were implanted via a promontory cochleostomy with full electrode insertions of Cochlear(TM) Nucleus® (Cochlear Nucleus, Cochlear Ltd, Australia) devices: 8 with straight electrodes and 13 with contoured electrodes. Baseline recordings were made after the completion of the posterior tympanotomy, and subsequently at stages of the cochleostomy and electrode insertion. We were unable to obtain recordings on five patients because the ear-insert tubing kinked, which disrupted transmission of the stimulus. Five had insufficient cochlear function to be able to record a baseline ECOG. No subjects in whom we were able to obtain a satisfactory baseline ECOG (n=11) had a reduction in ECOG action potential (AP) amplitude, morphology or threshold up to completion of the cochleostomy. Seven maintained an unchanged ECOG throughout the procedure to full insertion. An implant had to be replaced because of a faulty straight electrode in one patient. The amplitude significantly reduced during insertion of the replacement array. Two had a reduction in amplitude, threshold, and shape of the wave related to inadvertent suction of the perilymph. Subsequently, one maintained this changed ECOG to the end of the procedure, but the other progressed to complete loss of the ECOG during insertion of the array. One other subject had a significant reduction in the amplitude during insertion of the electrode from a depth of approximately 18mm to full insertion. Intra-operative monitoring of residual hearing may be possible in most patients undergoing cochlear implantation. This pilot study suggests that cochleostomy is not associated with intra-operative loss of residual hearing; ECOG can be preserved during the procedure in most patients; intra-operative loss of hearing is most likely to occur when the tip of the array reaches the basal turn of the cochlea. This risk may increase if the array has to be removed and re-inserted. Suction of perilymph causes immediate changes, which may not recover.
Waardenburg syndrome presents with dystopia canthorum, pigmentary abnormalities of hair, iris and... more Waardenburg syndrome presents with dystopia canthorum, pigmentary abnormalities of hair, iris and skin (often a white forelock and heterochromia iridis) and sensorineural deafness. The authors review the electrophysiological and psychophysical findings of implanted children with Waardenburg syndrome at the Sydney Cochlear Implant Centre. Twenty children with Waardenburg syndrome received cochlear implants between 1985 and 2001. Electrical auditory brainstem response (EABR) was performed in all of these patients intra-operatively as part of the routine investigations. Only 13 of these patients were assessed one year or more post-operatively by means of the Melbourne Categories (0-7). Four patients (20%) were found to have abnormal EABR recordings. The mode of Melbourne Categories in this group (n = 3) was 1 at one year post-operation. The other 16 patients were found to have normal EABR and the mode of Melbourne Categories in this group (n = 10) was 7. A poor outcome after cochlear implantation was associated with abnormal EABR recordings (a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;true&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; auditory neuropathy) and was found in a significant proportion of patients with Waardenburg syndrome.
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