Halit Sanli

Predicting cochlear implant outcomes in children with auditory neuropathy.

Objective: 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). Study Design: Retrospective cohort study. Setting: The Sydney Cochlear Implant Centre and the Childrens Hospital at Westmead. Patients: 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. Interventions: 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. Main Outcome Measures: Melbourne speech perception score (MSPS) at 1 year and implant evoked electric auditory brainstem response (EABR). Results: 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. Conclusion: 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.

Auditory neuropathy : An update

Objectives: 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. Methods: 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). Results: 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 < 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. Conclusions: 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.

Displacement of electrodes of a cochlear implant into the vestibular system: intra- and postoperative electrophysiological analyses.

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.

Meningitis resulting in hearing loss and labyrinthitis ossificans – does the causative organism matter?

Abstract Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause profound hearing loss and labyrinthitis ossificans. 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 ossification. 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 ossificans was more common after infection with Streptococcus pneumoniae but there was no statistically significant difference between Streptococcus pneumoniae, Haemophilus influenzae or Neisseria meningitidis for labyrinthitis ossificans (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 significantly higher risk. Copyright

Cochlear implantations in children with Waardenburg syndrome: an electrophysiological and psychophysical review.

Abstract 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 ‘true’ auditory neuropathy) and was found in a significant proportion of patients with Waardenburg syndrome. Copyright

The use of intra-operative electrical auditory brainstem responses to predict the speech perception outcome after cochlear implantation

Abstract Electrically evoked auditory brainstem responses (EABR) were obtained intra-operatively from children receiving full insertion of Cochlear CI24 implant. The EABR waveform was quantified 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. Significant 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 significant improvement. Copyright

Impedance, neural response telemetry, and speech perception outcomes after reimplantation of cochlear implants in children.

Objective To compare mean impedance levels, neural response telemetry (NRT), and auditory perception after initial and explant-reimplant pediatric cochlear implants. Study Design Retrospective case review. Setting Tertiary referral hospital and cochlear implant program. Patients Children 0 to 16 years inclusive who have undergone explant-reimplant of their cochlear implant. Intervention Impedance levels, NRT, and speech perception performance. Main Outcome Measures Impedance, NRT, and auditory perception at switch on, 3 months, 12 months, 3 years, and 5 years after initial cochlear implant and reimplantation. Results The explant-reimplant group receiving Cochlear contour array had significantly (p < 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. Conclusion 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.

Preliminary results and technique for electrophysiological intra-operative monitoring of residual hearing during cochlear implantation.

Abstract Aims To assess the feasibility of intra-operative monitoring of residual hearing using electrocochleography (ECOG) during cochlear implantation. We present our methods and preliminary results. Methods 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 CochlearTM 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. Results 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 18 mm to full insertion. Conclusions 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.

Pre-operative testing of patients with neuropathy or dys-synchrony

The use of the term “auditory neuropathy” (AN) has probably steered clinicians away from considering cochlear implantation in the past, as a “neuropathy” usually implies abnormal neural function and leads to the assumption that a cochlear implant is unlikely to be successful. However, since 2000 a number of studies have been published indicating that some patients diagnosed with AN did benefit from cochlear implantation.1 In these cases, it was not predicted before the operation whether or not the patients were likely to experience success. Auditory neuropathy (AN) has been typically characterized by absent or abnormal brainstem responses in the presence of otoacoustic emissions (OAEs) and/or a cochlear microphonic (CM). AN patients have been particularly difficult to manage, and the degree of their loss and level of distortion is unpredictable from auditory brainstem response (ABR) and OAE testing alone. Also, their puretone audiometry levels are often inconsistent with their speech-discrimination ability. Our experience at the Sydney Cochlear Implant Centre (SCIC) has shown that significant language delays can result even when hearing aid fittings have shown good detection of sound across the speech range. Some recent studies have shown that patients identified with AN show abnormal results on tests evaluating temporal processing, therefore suggesting “dys-synchronous” auditory activity.2,3 For an ABR waveform to be seen there must also be synchronous neural activity that is time-locked to the presentation of the stimulus. The term “auditory dys-synchrony” (AD) has therefore been put forward as a more appropriate description to use as it reflects the nature of the problem rather than implying the site of lesion based on incomplete information. If additional neurologic tests confirm the presence of an identifiable neurologic abnormality, then the term “auditory neuropathy” would appear more accurate. In a typical audiology clinic setting, the main tools available for the differential diagnosis of sensory and/or neural hearing losses include OAEs and ABR testing using acoustic stimuli (acABR). Unfortunately, OAEs provide information only about outer hair cell function and can be easily masked when there is middle ear pathology. It can also be difficult to make a differential diagnosis using acABR testing alone because when the ABR waveforms are absent or abnormal it may be unclear if this resulted from poor/abnormal cochlear stimulation of the auditory nerve or a true abnormality along the nerve and/or brainstem pathway. While performing OAE and acABR testing is an important way of flagging the presence of AN/AD, determining the site of lesion in these cases on the basis of these two tests alone is not possible.

Role of auditory stimulation in maturation of the auditory pathway

Objective To compare the maturation of the auditory pathway, as shown by electrical brainstem auditory potentials (EABRs), in ears with and without prior auditory stimulation. Material and Methods Electrophysiological data were collected prospectively from ears which had received cochlear implants. Implant-evoked (Imp)EABRs were recorded. Thirty children, implanted after January 2000, were selected according to a strict inclusion/exclusion protocol. All the children had received a 22-channel Nucleus cochlear implant (CI24 series). Intraoperatively, ImpEABRs were recorded using the Medelec Synergy® Evoked Response system in conjunction with Nucleus Neural Response Telemetry® software. The ImpEABR latencies of waves eII, eIII and eV and the morphology of wave eV were assessed. Results ImpEABRs alter during the first 12 months of life. The latency becomes shorter during this period and the morphology of wave eV alters from a broad shape to a more distinct waveform. This appears to occur independently, even in the absence of auditory stimulation. Conclusion The development of electrical brainstem auditory potentials is not dependent on auditory stimulation.