Temporal bone histopathology in a case of sensorineural hearing loss caused by superficial siderosis of the central nervous system and treated by cochlear implantation

Peripheral Neural Synchrony in Postlingually Deafened Adult Cochlear Implant Users

OBJECTIVES

This paper reports a noninvasive method for quantifying neural synchrony in the cochlear nerve (i.e., peripheral neural synchrony) in cochlear implant (CI) users, which allows for evaluating this physiological phenomenon in human CI users for the first time in the literature. In addition, this study assessed how peripheral neural synchrony was correlated with temporal resolution acuity and speech perception outcomes measured in quiet and in noise in postlingually deafened adult CI users. It tested the hypothesis that peripheral neural synchrony was an important factor for temporal resolution acuity and speech perception outcomes in noise in postlingually deafened adult CI users.

DESIGN

Study participants included 24 postlingually deafened adult CI users with a Cochlear™ Nucleus® device. Three study participants were implanted bilaterally, and each ear was tested separately. For each of the 27 implanted ears tested in this study, 400 sweeps of the electrically evoked compound action potential (eCAP) were measured at four electrode locations across the electrode array. Peripheral neural synchrony was quantified at each electrode location using the phase-locking value (PLV), which is a measure of trial-by-trial phase coherence among eCAP sweeps/trials. Temporal resolution acuity was evaluated by measuring the within-channel gap detection threshold (GDT) using a three-alternative, forced-choice procedure in a subgroup of 20 participants (23 implanted ears). For each ear tested in these participants, GDTs were measured at two electrode locations with a large difference in PLVs. For 26 implanted ears tested in 23 participants, speech perception performance was evaluated using consonant-nucleus-consonant (CNC) word lists presented in quiet and in noise at signal to noise ratios (SNRs) of +10 and +5 dB. Linear Mixed effect Models were used to evaluate the effect of electrode location on the PLV and the effect of the PLV on GDT after controlling for the stimulation level effects. Pearson product-moment correlation tests were used to assess the correlations between PLVs, CNC word scores measured in different conditions, and the degree of noise effect on CNC word scores.

RESULTS

There was a significant effect of electrode location on the PLV after controlling for the effect of stimulation level. There was a significant effect of the PLV on GDT after controlling for the effects of stimulation level, where higher PLVs (greater synchrony) led to lower GDTs (better temporal resolution acuity). PLVs were not significantly correlated with CNC word scores measured in any listening condition or the effect of competing background noise presented at an SNR of +10 dB on CNC word scores. In contrast, there was a significant negative correlation between the PLV and the degree of noise effect on CNC word scores for a competing background noise presented at an SNR of +5 dB, where higher PLVs (greater synchrony) correlated with smaller noise effects on CNC word scores.

CONCLUSIONS

This newly developed method can be used to assess peripheral neural synchrony in CI users, a physiological phenomenon that has not been systematically evaluated in electrical hearing. Poorer peripheral neural synchrony leads to lower temporal resolution acuity and is correlated with a larger detrimental effect of competing background noise presented at an SNR of 5 dB on speech perception performance in postlingually deafened adult CI users.

Peripheral neural synchrony in post-lingually deafened adult cochlear implant users

Objective

This paper reports a noninvasive method for quantifying neural synchrony in the cochlear nerve (i.e., peripheral neural synchrony) in cochlear implant (CI) users, which allows for evaluating this physiological phenomenon in human CI users for the first time in the literature. In addition, this study assessed how peripheral neural synchrony was correlated with temporal resolution acuity and speech perception outcomes measured in quiet and in noise in post-lingually deafened adult CI users. It tested the hypothesis that peripheral neural synchrony was an important factor for temporal resolution acuity and speech perception outcomes in noise in post-lingually deafened adult CI users.

Design

Study participants included 24 post-lingually deafened adult CI users with a Cochlear™ Nucleus® device. Three study participants were implanted bilaterally, and each ear was tested separately. For each of the 27 implanted ears tested in this study, 400 sweeps of the electrically evoked compound action potential (eCAP) were measured at four electrode locations across the electrode array. Peripheral neural synchrony was quantified at each electrode location using the phase locking value (PLV), which is a measure of trial-by-trial phase coherence among eCAP sweeps/trials. Temporal resolution acuity was evaluated by measuring the within-channel gap detection threshold (GDT) using a three-alternative, forced-choice procedure in a subgroup of 20 participants (23 implanted ears). For each ear tested in these participants, GDTs were measured at two electrode locations with a large difference in PLVs. For 26 implanted ears tested in 23 participants, speech perception performance was evaluated using Consonant-Nucleus-Consonant (CNC) word lists presented in quiet and in noise at signal-to-noise ratios (SNRs) of +10 and +5 dB. Linear Mixed effect Models were used to evaluate the effect of electrode location on the PLV and the effect of the PLV on GDT after controlling for the stimulation level effects. Pearson product-moment correlation tests were used to assess the correlations between PLVs, CNC word scores measured in different conditions, and the degree of noise effect on CNC word scores.

Results

There was a significant effect of electrode location on the PLV after controlling for the effect of stimulation level. There was a significant effect of the PLV on GDT after controlling for the effects of stimulation level, where higher PLVs (greater synchrony) led to lower GDTs (better temporal resolution acuity). PLVs were not significantly correlated with CNC word scores measured in any listening condition or the effect of competing background noise presented at a SNR of +10 dB on CNC word scores. In contrast, there was a significant negative correlation between the PLV and the degree of noise effect on CNC word scores for a competing background noise presented at a SNR of +5 dB, where higher PLVs (greater synchrony) correlated with smaller noise effects on CNC word scores.

Conclusions

This newly developed method can be used to assess peripheral neural synchrony in CI users, a physiological phenomenon that has not been systematically evaluated in electrical hearing. Poorer peripheral neural synchrony leads to lower temporal resolution acuity and is correlated with a larger detrimental effect of competing background noise presented at a SNR of 5 dB on speech perception performance in post-lingually deafened adult CI users.

Relationships Between the Auditory Nerve Sensitivity to Amplitude Modulation, Perceptual Amplitude Modulation Rate Discrimination Sensitivity, and Speech Perception Performance in Postlingually Deafened Adult Cochlear Implant Users

OBJECTIVE

This study assessed the relationships between the salience of amplitude modulation (AM) cues encoded at the auditory nerve (AN), perceptual sensitivity to changes in AM rate (i.e., AM rate discrimination threshold, AMRDT), and speech perception scores in postlingually deafened adult cochlear implant (CI) users.

DESIGN

Study participants were 18 postlingually deafened adults with Cochlear Nucleus devices, including five bilaterally implanted patients. For each of 23 implanted ears, neural encoding of AM cues at 20 Hz at the AN was evaluated at seven electrode locations across the electrode array using electrophysiological measures of the electrically evoked compound action potential (eCAP). The salience of AM neural encoding was quantified by the Modulated Response Amplitude Ratio (MRAR). Psychophysical measures of AMRDT for 20 Hz modulation were evaluated in 16 ears using a three-alternative, forced-choice procedure, targeting 79.4% correct on the psychometric function. AMRDT was measured at up to five electrode locations for each test ear, including the electrode pair that showed the largest difference in the MRAR. Consonant-Nucleus-Consonant (CNC) word scores presented in quiet and in speech-shaped noise at a signal to noise ratio (SNR) of +10 dB were measured in all 23 implanted ears. Simulation tests were used to assess the variations in correlation results when using the MRAR and AMRDT measured at only one electrode location in each participant to correlate with CNC word scores. Linear Mixed Models (LMMs) were used to evaluate the relationship between MRARs/AMRDTs measured at individual electrode locations and CNC word scores. Spearman Rank correlation tests were used to evaluate the strength of association between CNC word scores measured in quiet and in noise with (1) the variances in MRARs and AMRDTs, and (2) the averaged MRAR or AMRDT across multiple electrodes tested for each participant.

RESULTS

There was no association between the MRAR and AMRDT. Using the MRAR and AMRDT measured at only one, randomly selected electrode location to assess their associations with CNC word scores could lead to opposite conclusions. Both the results of LMMs and Spearman Rank correlation tests showed that CNC word scores measured in quiet or at 10 dB SNR were not significantly correlated with the MRAR or AMRDT. In addition, the results of Spearman Rank correlation tests showed that the variances in MRARs and AMRDTs were not significantly correlated with CNC word scores measured in quiet or in noise.

CONCLUSIONS

The difference in AN sensitivity to AM cues is not the primary factor accounting for the variation in AMRDTs measured at different stimulation sites within individual CI users. The AN sensitivity to AM per se may not be a crucial factor for CNC word perception in quiet or at 10 dB SNR in postlingually deafened adult CI users. Using electrophysiological or psychophysical results measured at only one electrode location to correlate with speech perception scores in CI users can lead to inaccurate, if not wrong, conclusions.

Progressive loss of hearing and balance in superficial siderosis due to occult spinal dural defects

PURPOSE

Superficial siderosis, a progressive, debilitating, neurological disease, often presents with bilateral impairment of auditory and vestibular function. We highlight that superficial siderosis is often due to a repairable spinal dural defect of the type that can also cause spontaneous intracranial hypotension.

METHODS

Retrospective chart review of five patients presenting with moderate to severe, progressive bilateral sensorineural hearing loss as well as vestibular loss. All patients had developed superficial siderosis from spinal dural defects: three after trauma, one after spinal surgery and one from a thoracic discogenic microspur.

RESULTS

The diagnosis was made late in all five patients; despite surgical repair in four, hearing and vestibular loss failed to improve.

CONCLUSIONS

In patients presenting with progressive bilateral sensorineural hearing loss, superficial siderosis should be considered as a possible cause. If these patients also have bilateral vestibular loss, cerebellar impairment and anosmia, then the diagnosis is likely and the inevitable disease progress might be halted by finding and repairing the spinal dural defect.

Postlingually Deafened Adult Cochlear Implant Users With Prolonged Recovery From Neural Adaptation at the Level of the Auditory Nerve Tend to Have Poorer Speech Perception Performance

OBJECTIVE

This study investigated the effects of two temporal response properties of the auditory nerve (i.e., neural adaptation and recovery from neural adaptation) on speech perception performance in postlingually deafened adult cochlear implant (CI) users.

DESIGN

Study participants included 18 postlingually deafened adults who were Cochlear Nucleus device users with a full electrode array insertion in the test ear(s). Neural adaptation and adaptation recovery of the auditory nerve (AN) were evaluated using electrophysiological measures of the electrically evoked compound action potential (eCAP). The amount of neural adaptation was quantified by the adaptation index within three time windows: 0 to 8.89 (window 1), 44.44 to 50.00 (window 2), and 94.44 to 100.00 ms (window 3). The speed of neural adaptation was estimated using a two-parameter power law function. To evaluate adaptation recovery of the AN, eCAPs to the last pulse of the 100-ms pulse train were recorded at masker-probe-intervals ranging from 1.054 to 256 ms in logarithmic steps. The amount of adaptation recovery was quantified by the adaptation recovery ratio. The time-constant of adaptation recovery was estimated using an exponential function with up to three components. Speech perception performance was evaluated by measuring consonant-nucleus-consonant (CNC) word scores presented in quiet and in speech-shaped noise at a signal-to-noise ratio (SNR) of +10 dB. One-tailed Pearson Product Moment correlation tests were used (1) to assess the associations among parameters of neural adaptation and adaptation recovery and (2) to evaluate the strength of association between these parameters and CNC word scores measured in quiet and in noise. The contributions of different parameters quantifying neural adaptation and adaptation recovery on speech perception scores were evaluated using multivariable linear regression analyses.

RESULTS

The Pearson Product Moment correlation coefficient demonstrated a moderate, negative correlation between the speed of adaptation recovery and CNC word scores measured in quiet and in noise. The speed of adaptation recovery accounted for 14.1% of variability in CNC word scores measured in quiet and 16.7% of variability in CNC word scores measured in noise. The correlation strengths between CNC word scores and the adaptation index, the adaptation recovery ratio and the speed of neural adaptation ranged from negligible to weak.

CONCLUSIONS

The speed of adaptation recovery plays a more important role than other features of neural adaptation and adaptation recovery of the AN in speech perception in postlingually deafened adult CI users. Patients with prolonged adaptation recovery tend to show poorer speech perception performance.

Neural Adaptation of the Electrically Stimulated Auditory Nerve Is Not Affected by Advanced Age in Postlingually Deafened, Middle-aged, and Elderly Adult Cochlear Implant Users

OBJECTIVE

This study aimed to investigate the associations between advanced age and the amount and the speed of neural adaptation of the electrically stimulated auditory nerve (AN) in postlingually deafened adult cochlear implant (CI) users.

DESIGN

Study participants included 26 postlingually deafened adult CI users, ranging in age between 28.7 and 84.0 years (mean: 63.8 years, SD: 14.4 years) at the time of testing. All study participants used a Cochlear Nucleus device with a full electrode array insertion in the test ear. The stimulus was a 100-ms pulse train with a pulse rate of 500, 900, 1800, or 2400 pulses per second (pps) per channel. The stimulus was presented at the maximum comfortable level measured at 2400 pps with a presentation rate of 2 Hz. Neural adaptation of the AN was evaluated using electrophysiological measures of the electrically evoked compound action potential (eCAP). The amount of neural adaptation was quantified by the adaptation index (AI) within three time windows: around 0 to 8 ms (window 1), 44 to 50 ms (window 2), and 94 to 100 ms (window 3). The speed of neural adaptation was quantified using a two-parameter power law estimation. In 23 participants, four electrodes across the electrode array were tested. In three participants, three electrodes were tested. Results measured at different electrode locations were averaged for each participant at each pulse rate to get an overall representation of neural adaptation properties of the AN across the cochlea. Linear-mixed models (LMMs) were used (1) to evaluate the effects of age at testing and pulse rate on the speed of neural adaptation and (2) to assess the effects of age at testing, pulse rate, and duration of stimulation (i.e., time window) on the amount of neural adaptation in these participants.

RESULTS

There was substantial variability in both the amount and the speed of neural adaptation of the AN among study participants. The amount and the speed of neural adaptation increased at higher pulse rates. In addition, larger amounts of adaptation were observed for longer durations of stimulation. There was no significant effect of age on the speed or the amount of neural adaptation.

CONCLUSIONS

The amount and the speed of neural adaptation of the AN are affected by both the pulse rate and the duration of stimulation, with higher pulse rates and longer durations of stimulation leading to faster and greater neural adaptation. Advanced age does not affect neural adaptation of the AN in postlingually deafened, middle-aged and elderly adult CI users.

Characteristics of the Adaptation Recovery Function of the Auditory Nerve and Its Association With Advanced Age in Postlingually Deafened Adult Cochlear Implant Users

OBJECTIVE

This study aimed to (1) characterize the amount and the speed of recovery from neural adaptation at the auditory nerve (AN) and (2) assess their associations with advanced age in postlingually deafened adult cochlear implant users.

DESIGN

Study participants included 25 postlingually deafened adult, Cochlear Nucleus device users, ranging in age between 24.83 and 83.21 years at the time of testing. The stimulus was a 100-ms pulse train presented at four pulse rates: 500, 900, 1800, and 2400 pulses per second (pps). The pulse trains were presented at the maximum comfortable level measured for the 2400-pps pulse train. The electrically evoked compound action potential (eCAP) evoked by the last pulse of the pulse train (i.e., the probe pulse) was recorded. The remaining pulses of the pulse train served as the pulse-train masker. The time interval between the probe pulse and the last pulse of the pulse-train masker [i.e., masker-probe-interval (MPI)] systematically increased from 0.359 ms up to 256 ms. The adaptation recovery function (ARF) was obtained by plotting normalized eCAP amplitudes (re: the eCAP amplitude measured at the MPI of 256 ms) as a function of MPIs. The adaptation recovery ratio (ARR) was defined as the ratio between the eCAP amplitude measured at the MPI of 256 ms and that measured for the single-pulse stimulus presented at the same stimulation level. The time constants of the ARF were estimated using a mathematical model with an exponential function with up to three components. Generalized Linear Mixed effects Models were used to compare ARRs and time constants measured at different electrode locations and pulse rates, as well as to assess the effect of advanced age on these dependent variables.

RESULTS

There were three ARF types observed in this study. The ARF type observed in the same study participant could be different at different electrode locations and/or pulse rates. Substantial variations in both the amount and the speed of neural adaptation recovery among study participants were observed. The ARR was significantly affected by pulse rate but was not affected by electrode location. The effect of electrode location on the time constants of the ARF was not statistically significant. Pulse rate had a statistically significant effect on τ 1, but not on τ 2 or τ 3 . There was no statistically significant effect of age on the ARR or the time constants of the ARF.

CONCLUSIONS

Neural adaptation recovery processes at the AN demonstrate substantial variations among human cochlear implant users. The recovery pattern can be nonmonotonic with up to three phases. While the amount of neural adaptation recovery decreases as pulse rate increases, only the speed of the first phase of neural adaptation recovery is affected by pulse rate. Electrode location or advanced age has no robust effect on neural adaptation recovery processes at the level of the AN for a 100-ms pulse-train masker with pulse rates of 500 to 2400 pps. The lack of sufficient participants in this study who were 40 years of age or younger at the time of testing might have precluded a thorough assessment of the effect of advanced age.

Cochlea implantation in patients with superficial hemosiderosis

Introduction

Superficial hemosiderosis is a sub-form of hemosiderosis in which the deposits of hemosiderin in the central nervous system damage the nerve cells. This form of siderosis is caused by chronic cerebral hemorrhages, especially subarachnoid hemorrhages. The diversity of symptoms depends on the respective damage to the brain, but in most of the cases it shows up as incipient unilateral or bilateral hearing loss, ataxia and signs of pyramidal tracts. We are investigating the question of whether cochlear implantation is a treatment option for patients with superficial hemosiderosis and which strategy of diagnostic procedure has to be ruled out preoperatively.

Materials and methods

In a tertiary hospital between 2009 and 2018, we examined (N = 5) patients with radiologically confirmed central hemosiderosis who suffered from profound hearing loss to deafness were treated with a cochlear implant (CI). We compared pre- and postoperative speech comprehension (Freiburg speech intelligibility test for monosyllables and HSM sentence test).

Results

Speech understanding improved on average by 20% (monosyllabic test in the Freiburg speech intelligibility test) and by 40% in noise (HSM sentence test) compared to preoperative speech understanding with optimized hearing aids.

Discussion

The results show that patients with superficial siderosis benefit from CI with better speech understanding. The results are below the average for all postlingual deaf CI patients. Superficial siderosis causes neural damages, which explains the reduced speech understanding based on central hearing loss. It is important to correctly weigh the patient's expectations preoperatively and to include neurologists within the therapy procedure.

The Effect of Pulse Polarity on Neural Response of the Electrically Stimulated Cochlear Nerve in Children With Cochlear Nerve Deficiency and Children With Normal-Sized Cochlear Nerves

OBJECTIVE

This study aimed to (1) investigate the effect of pulse polarity on neural response of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency (CND) and children with normal-sized cochlear nerves and (2) compare the size of the pulse polarity effect between these two subject groups.

DESIGN

The experimental and control group included 31 children with CND and 31 children with normal-sized cochlear nerves, respectively. For each study participant, evoked compound action potential (eCAP) input/output (I/O) functions for anodic-leading and cathodic-leading biphasic stimuli were measured at three electrode locations across the electrode array. The dependent variables of interest included the eCAP amplitude measured at the maximum comfortable level of the anodic stimulus, the lowest level that could evoke an eCAP (i.e., the eCAP threshold), the slope of the eCAP I/O function estimated based on linear regression, the negative-peak (i.e., N1) latency of the eCAP, as well as the size of the pulse polarity effect on these eCAP measurements. Generalized linear mixed effect models were used to compare the eCAP amplitude, the eCAP threshold, the slope of the eCAP I/O function, and the N1 latency evoked by the anodic-leading stimulus with those measured for the cathodic-leading stimulus for children with CND and children with normal-sized cochlear nerves. Generalized linear mixed effect models were also used to compare the size of the pulse polarity effect on the eCAP between these two study groups. The one-tailed Spearman correlation test was used to assess the potential correlation between the pulse phase duration and the difference in N1 latency measured for different pulse polarities.

RESULTS

Compared with children who had normal-sized cochlear nerves, children with CND had reduced eCAP amplitudes, elevated eCAP thresholds, flatter eCAP I/O functions, and prolonged N1 latencies. The anodic-leading stimulus led to higher eCAP amplitudes, lower eCAP thresholds, and shorter N1 latencies than the cathodic-leading stimulus in both study groups. Steeper eCAP I/O functions were recorded for the anodic-leading stimulus than those measured for the cathodic-leading stimulus in children with CND, but not in children with normal-sized cochlear nerves. Group differences in the size of the pulse polarity effect on the eCAP amplitude, the eCAP threshold, or the N1 latency were not statistically significant.

CONCLUSIONS

Similar to the normal-sized cochlear nerve, the hypoplastic cochlear nerve is more sensitive to the anodic-leading than to the cathodic-leading stimulus. Results of this study do not provide sufficient evidence for proving the idea that the pulse polarity effect can provide an indication for local neural health.

The Effect of Interphase Gap on Neural Response of the Electrically Stimulated Cochlear Nerve in Children With Cochlear Nerve Deficiency and Children With Normal-Sized Cochlear Nerves

OBJECTIVES

This study aimed to compare the effects of increasing the interphase gap (IPG) on the neural response of the electrically stimulated cochlear nerve (CN) between children with CN deficiency (CND) and children with normal-sized CNs.

DESIGN

Study participants included 30 children with CND and 30 children with normal-sized CNs. All subjects were implanted with a Cochlear Nucleus device with the internal electrode array 24RE[CA] in the test ear. The stimulus was a charge-balanced, cathodic leading, biphasic pulse with a pulse-phase duration of 50 μsec. For each subject, the electrically evoked compound action potential (eCAP) input/output (I/O) function was measured for 6 IPGs (i.e., 7, 14, 21, 28, 35, and 42 μsec) at 3 electrode locations across the electrode array. For each subject and each testing electrode, the highest stimulation used to measure the eCAP I/O function was the maximum comfortable level measured with an IPG of 42 μsec. Dependent variables (DVs) were the maximum eCAP amplitude, the eCAP threshold, and the slope of the eCAP I/O function estimated using both linear and sigmoidal regression functions. For each DV, the size of the IPG effect was defined as the proportional change relative to the result measured for the 7 μsec IPG at the basal electrode location. Generalized linear mixed effect models with subject group, electrode location, and IPG duration as the fixed effects and subject as the random effect were used to compare these DVs and the size of the IPG effect on these DVs.

RESULTS

Children with CND showed smaller maximum eCAP amplitudes, higher eCAP thresholds, and smaller slopes of eCAP I/O function estimated using either linear or sigmoidal regression function than children with normal-sized CNs. Increasing the IPG duration resulted in larger maximum eCAP amplitudes, lower eCAP thresholds and larger slopes of eCAP I/O function estimated using sigmoidal regression function at all three electrode locations in both study groups. Compared with children with normal-sized CNs, children with CND showed larger IPG effects on both the maximum eCAP amplitude and the slope of the eCAP I/O function estimated using either linear or sigmoidal regression function, and a smaller IPG effect on the eCAP threshold than those measured in children with normal-sized CNs.

CONCLUSIONS

Increasing the IPG increases responsiveness of the electrically stimulated CN in both children with CND and children with normal-sized CNs. The maximum eCAP amplitude and the slope of the eCAP I/O function measured in human listeners with poorer CN survival are more sensitive to changes in the IPG. In contrast, the eCAP threshold in listeners with poorer CN survival is less sensitive to increases in the IPG. Further studies are warranted to identify the best parameters of eCAP results for predicting CN survival before this eCAP testing paradigm can be used as a clinical tool for evaluating neural health for individual cochlear implant patients.

Meta-Analysis-Correlation between Spiral Ganglion Cell Counts and Speech Perception with a Cochlear Implant

The presence of spiral ganglion cells (SGCs) is widely accepted to be a prerequisite for successful speech perception with a cochlear implant (CI), because SGCs provide the only known conduit between the implant electrode and the central auditory system. By extension, it has been hypothesized that the number of SGCs might be an important factor in CI outcomes. An impressive body of work has been published on findings from the laborious process of collecting temporal bones from CI users and counting the number of SGCs to correlate those numbers with speech perception scores, but the findings thus far have been conflicting. We performed a meta-analysis of all published studies with the hope that combining existing data may help us reach a more definitive conclusion about the relationship between SGC count and speech perception scores in adults.

A Case of Cochlear Implantation in a Patient with Superficial Siderosis

Superficial siderosis is a disease in which iron from hemoglobin is deposited in the central nervous system, resulting in conditions such as progressive sensorineural hearing loss, cerebellar ataxia, dementia, and pyramidal signs. A 30-year-old man with superficial siderosis received a cochlear implant in the left ear, which had shown complete hearing loss. Good auditory responses were obtained at 14 days after implantation. The postoperative average hearing level with the cochlear implant was 56.7 dB at 3 months and 55.0 dB at 6 months. However, the patient showed gradual hearing loss, and the dynamic range changed each time the electrode parameters were adjusted. To assess residual hearing ability, single-photon emission computed tomography was performed together with an assessment of electrical auditory brainstem response, which showed a good response and increased blood flow in both the temporal lobes. Based on this result, we asked the patient to continue using the cochlear implant to see whether a perception of speech response would be obtained. However, the patient discontinued using the cochlear implant because he could not hear satisfactorily. Hearing outcomes after cochlear implant surgery for patients with superficial siderosis are not necessarily good. Therefore, the possibility of unsatisfactory results should be fully explained before recommending this surgery to patients.

Case Report: Auditory Neuropathy and Central Auditory Processing Deficits in a Neuro-Otological Case-Study of Infratentorial Superficial Siderosis

Hearing and balance impairment are the most frequently reported features of infratentorial (classical) superficial siderosis (iSS). There are few comprehensive descriptions of audiovestibular function in iSS and therefore limited understanding of the affected segment(s) of the audiovestibular pathway. In addition, monitoring disease progression and response to treatment is challenging and currently mainly guided by subjective patient reports and magnetic resonance imaging. To the best of our knowledge, there have been no previous reports assessing central auditory function in iSS. We describe such findings in a patient with iSS in an attempt to precisely localize the site of the audiovestibular dysfunction, determine its severity and functional impact. We confirm the presence of (asymmetrical) auditory neuropathy and identify central auditory processing deficits, suggesting involvement of the central auditory pathway beyond the brainstem. We correlate the audiological and vestibular findings with self-report measures and the siderosis appearances on brain magnetic resonance images.

Outcomes of Cochlear Implantation in Patients with Superficial Siderosis: A Systematic Review and Narrative Synthesis

This study aimed to establish outcomes following cochlear implantation (CI) in patients with superficial siderosis (SS). MEDLINE, Embase, Web of Science, Cochrane, and ClinicalTrials.gov databases were searched for this systematic review. No limits were placed on the language or the year of publication. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Of a total of 46 studies, 19 studies met the inclusion criteria reporting outcomes in 38 patients. Of the 44 implants, 23 implants (52.27%) had good hearing outcomes at the last follow-up, 9 (20.45%) were initially beneficial for the patient, but then the performance deteriorated (4 of which were re-implanted), and 12 (27.27%) were not beneficial for the patient. All studies were classified as grade 4 studies using the Oxford Centre for Evidence-Based Medicine (OCEBM) grading system, being retrospective in nature and consisting of case reports and noncontrolled case series with a small number of patients. Of the 44 implants, 32 (72.73%) showed improved hearing outcomes following CI for SS at some point in time, of which 23 (52.2%) implants showed sustained benefit at the last follow-up (average follow-up time was 21.97 months). It is difficult to predict the longevity of benefit owing to the progressive nature of the disease or the patients in whom it may be beneficial, as the preoperative investigations inadequately predict benefit. Preimplantation and postimplantation counseling with the patient and their family regarding the potential limited benefit and eventual parallel decline with the neurological disease are crucial, along with thorough clinical investigations.

Frequency, Extent, and Correlates of Superficial Siderosis and Ependymal Siderosis in Premature Infants with Germinal Matrix Hemorrhage: An SWI Study

BACKGROUND AND PURPOSE

Germinal matrix intraventricular hemorrhage is a common complication of prematurity. An underrecognized complication of germinal matrix intraventricular hemorrhage is superficial siderosis, and the clinical consequences of superficial siderosis are not well-known. We aimed to investigate the prevalence, anatomic distribution, and severity of superficial siderosis and ependymal siderosis in premature infants with germinal matrix intraventricular hemorrhage using SWI.

MATERIALS AND METHODS

In this retrospective study, we included 88 patients across all grades of germinal matrix intraventricular hemorrhage who underwent MR imaging at term-equivalent age. Images were evaluated for the presence, distribution, and severity of superficial siderosis and ependymal siderosis. Univariate and multivariate logistic regression analyses were performed to determine factors associated with superficial siderosis and ependymal siderosis. The agreement among T1, T2, and SWI sequences was examined.

RESULTS

Seventy-two patients had brain stem superficial siderosis, and 79 patients had ependymal siderosis. The presence, extent, and severity of superficial siderosis and ependymal siderosis were closely related to the grade of germinal matrix intraventricular hemorrhage and intraventricular hematoma volume. Brain stem superficial siderosis had a stronger correlation with intraventricular hemorrhage than with cerebellar hemorrhage. Compared with SWI, T1 and T2 sequences detected only small proportions of patients with superficial siderosis (12.5% and 6.9%, respectively).

CONCLUSIONS

The incidence of superficial siderosis and ependymal siderosis is very high in preterm infants with germinal matrix intraventricular hemorrhage when assessed by SWI at term-equivalent age. The presence and extent of superficial siderosis and ependymal siderosis are closely related to germinal matrix intraventricular hemorrhage grade and intraventricular hematoma volume. Additional prospective studies using SWI are needed to clearly determine the clinical consequences of germinal matrix intraventricular hemorrhage with superficial siderosis and ependymal siderosis.

Vestibular Dysfunction in Patients With Superficial Siderosis of the Central Nervous System

OBJECTIVE

To describe the vestibular function in patients with superficial siderosis of the central nervous system (SSCN).

STUDY DESIGN

Retrospective analysis.

SETTING

Tertiary referral center.

PATIENTS

Ten consecutive patients with SSCN. This study is the largest case series of SSCN in which detailed neuro-otological findings, including electronystagmography recording, video head impulse test (vHIT), and posturography, were described.

INTERVENTIONS

Audiological and neuro-otological examinations, including pure-tone audiometry, distortion product otoacoustic emissions, speech audiometry, auditory brainstem responses, electronystagmography recording, vHIT, and posturography.

MAIN OUTCOME MEASURES

Pure-tone average, DP level, maximum speech discrimination score, interpeak latency between auditory brainstem responses waves I and V, eye tracking test, examination of optokinetic nystagmus, caloric response, visual suppression, vestibulo-ocular reflex gains, total center of pressure path length, and Romberg's ratio.

RESULTS

Audiological examinations suggested that the sensorineural hearing loss was of a cochlear etiology in 3 ears, a retrocochlear etiology in 11 ears, and a combined cochlear and retrocochlear etiology in 6 ears. Neuro-otological examinations revealed that eight out of nine patients had cerebellar disorders, while all patients also had peripheral vestibular dysfunction.

CONCLUSION

In addition to cerebellar disorders, SSCN patients suffer from severe peripheral vestibular dysfunction, which can exacerbate the patient's imbalance. When otolaryngologists encounter patients with distinctly progressive sensorineural hearing loss and imbalance, they should include SSCN in the differential diagnosis and perform neuro-otological examinations, including an electronystagmography recording and vHIT and brain magnetic resonance imaging.

Electrophysiological detection of electrode fold-over in perimodiolar cochlear implant electrode arrays: a multi-center study case series

PURPOSE

It is important for the surgeon to determine the position of the CI electrode array during and after its placement within the cochlea. Most preferably, this should be within the scala tympani to obtain the best audiological outcome. Thus, misplacement into the scala vestibuli or tip fold-over should be prevented. Since there are different ways to ensure proper positioning of the electrode array within the scala tympani (e.g., intraoperative radiography, electrophysiological recordings), our study was aimed at detecting intraoperative electrophysiologic characteristics to better understand the mechanisms of those electrode tip fold-overs.

MATERIAL AND METHODS

In a multi-centric, retrospective case-control series, patients with a postoperatively by radiography detected tip fold-over in perimodiolar electrodes were included. The point of fold-over (i.e., the electrode position) was determined and the intraoperative Auto-NRT recordings were analysed and evaluated.

RESULTS

Four patients were found to have an electrode tip fold-over (out of 85 implantees). Significant changes of the Auto-NRT recordings were not detected. All tip fold-overs occurred in the most apical part of the electrodes.

DISCUSSION

Cochlear implantation for hearing impaired patients plays a decisive role in modern auditory rehabilitation. Perimodiolar electrode arrays may fold over during the insertion and, hence, could have a negative impact on audiological outcome. Characteristic electrophysiologic changes to possibly predict this were not found in our series.

Accuracy of intraoperative electrophysiological testing in confirming correct cochlear implant electrode positions

Objective: To investigate the accuracy of intraoperative electrophysiological studies in detecting incorrectly positioned electrodes in cochlear implant surgery. Study design: A retrospective chart review. Setting: Tertiary referral centre. Patients: In total, 104 consecutive patients with a mean age of 5 years underwent cochlear implant surgery at our centre between January 2012 and December 2013. All patients were implanted with Cochlear Nucleus Freedom implants. Method: A retrospective study to compare intraoperative neural response telemetry (NRT), impedance and electrode position using Stenver's transorbital plain X-ray view. Results: Intraoperative electrophysiological tests for patients with Cochlear Nucleus Freedom implants showed 97% sensitivity and 100% specificity compared with postoperative X-ray imaging. Conclusion: NRT results for the position of cochlear implants were very accurate when checked by X-ray imaging showing that this technique is sufficient in most cases. Stenver's plain X-ray view is needed in complicated cases with abnormal NRT testing or difficult electrode insertion.

Superficial Siderosis of the Central Nervous System: Neurotological Findings Related to Magnetic Resonance Imaging

OBJECTIVE

To compare the neurotological results of five patients suffering from progressive hearing loss and ataxia due to superficial siderosis (SS) with the magnetic resonance imaging (MRI) findings.

STUDY DESIGN

Retrospective case review.

SETTING

Primary and hospital care center.

PARTICIPANTS

Five adult patients with neurotological symptoms of SS underwent MRI with acquisition of our temporal bone protocol including 3D-constructive interference in steady state (3D-CISS) and susceptibility-weighted imaging (SWI). All patients underwent a complete neurotological examination, the results of which were compared with the imaging findings.

MAIN OUTCOME MEASURES

Cochleovestibular deficits were present in all five patients as determined by uni- or bilateral bithermal caloric testing and/or video head impulse tests. Sacculocollic reflex was present with increased P1 and N1 latencies on both sides in all patients. MRI revealed an extensive hypointense SWI signal outlining the surface of the brain and the VIIIth cranial nerve in all five patients. Desynchronization of the brainstem auditory evoked potentials (BAEP) and partial or complete absence of the visual suppression of vestibulo-ocular reflex during the pendular rotatory test was particularly consistent with the lesions of the cochleovestibular nerves as well as the cerebellar atrophy seen on MRI.

CONCLUSION

The MRI results with SWI were related to neurotological findings in patients suffering from sensorineural deafness with ataxia due to SS. Our findings support the integration of the SWI and 3D-CISS sequences into the MRI protocol for all patients referred for evaluation of the extent of SS.

Bilateral Vestibulopathy in Superficial Siderosis

Background: Superficial siderosis (SS) is a rare condition in which hemosiderin, an iron storage complex, is deposited in neural tissues because of recurrent subarachnoid bleeding. Hemosiderin deposition in the vestibulocochlear nerve (CN VIII), brain, spinal cord and peripheral nerve can cause sensorineural hearing loss (SNHL) and postural imbalance, but much remains unknown about the vestibular manifestations of SS.

Objectives: To report the clinical course, cochleovestibular status, and patterns of vestibulopathy during follow-up of a relatively large case series, and to discuss the possible pathophysiological mechanism of vestibular deterioration.

Methods: Six patients diagnosed with SS by magnetic resonance imaging (MRI) were enrolled. Their medical records and radiological findings were retrospectively reviewed, particularly in terms of progression of the vestibulocochlear manifestations and the radiological characteristics.

Results: All six patients had SNHL. Five of them exhibited progressive hearing loss over years, which was asymmetric in four. On their most recent evaluations, patients showed cerebellar ataxia with combined central and peripheral vestibulopathy on both sides (n = 4), a bilateral peripheral vestibulopathy (n = 1) or isolated central vestibulopathy (n = 1). Notably, the former four patients showed an evolution of isolated central vestibulopathy into combined central and peripheral vestibulopathy. Hypo-intense lesions on T2 weighted MRIs were evident around the cerebellum in all patients, but such lesions were observed around the brainstem in five and the CN VIII in four. The cochlea-vestibular dysfunction generally progressed asymmetrically, but no left-right asymmetry was evident on MRI.

Conclusions: SS typically presents as bilaterally asymmetric, progressive cochleovestibular dysfunction with cerebellar ataxia. The pattern of vestibular dysfunction is usually combined central and peripheral vestibulopathy on both sides. Thus, precise identification of audiovestibular dysfunction and central signs is essential in SS, and patients with SS should undergo regular, comprehensive neurotological evaluation to optimize their treatments and prognosis.

Focused Neuro-Otological Review of Superficial Siderosis of the Central Nervous System

Background

Infratentorial siderosis (iSS) is a progressive degenerative disorder targeting primarily the cerebellum and cranial nerve eighth; therefore, progressive ataxia and its neuro-otological findings are common. Toxicity from hemosiderin involves selectively vulnerable neurons and glia in these posterior fossa structures. Other neurologic findings may be present, though our focus relates to the cochlea-vestibular cerebellar involvement. Radiographic evidence of siderosis may be the result of recurrent, albeit covert bleeding in the subarachnoid space, or the consequence of an overt post-traumatic or aneurysmal subarachnoid hemorrhage (SAH). The radiographic iSS appearance is identical regardless of the SAH cause. A recent study provides compelling evidence to search and correct possible hemorrhage sources in the spinal canal. The removal of residual existing hemosiderin deposits that may potentially cause clinical symptoms remains as a major therapeutic challenge.

Methods

We reviewed large data sources and identified salient papers that describe the pathogenesis, clinical and neurotologic manifestations, and the radiographic features of iSS.

Results

The epidemiology of iSS is unknown. In a recent series, clinically evident iSS was associated with recurrent SAH; by contrast, in a follow-up period ranging from weeks up to 11 years after a monophasic episode of SAH, radiographic siderosis was clinically silent. However, the post-aneurysmal or post-trauma SAH sample size in this single study was small and their observation period relatively short; moreover, the burden of intraneuronal hemosiderin is likely greater with recurrent SAH. There are a few reports of late iSS, several decades after traumatic SAH. A recent report found subjective hearing loss in aneurysmal SAH individuals with radiographic siderosis. Only in recent years, it is safe to perform magnetic resonance imaging (MRI) in post-aneurysmal SAH, because of the introduction of titanium, MRI-compatible aneurysm clips.

Conclusion

iSS can be associated with significant neurotologic and cerebellar morbidity; the recurrent SAH variant is frequently clinically symptomatic, has a shorter latency and greater neurotologic disability. In these cases, a thorough search and management of a covert source of bleeding may stop clinical progression. The frequency and clinical course of radiographic iSS after traumatic and post-aneurysmal SAH is largely unknown. Detection of radiographic iSS after trauma or aneurysm bleeding suggests that the slower clinical course could benefit from an effective intervention if it became available. The use of cochlear implants is a valid alternative with advanced hearing impairment.

Radiological and NRT-Ratio-Based Estimation of Slim Straight Cochlear Implant Electrode Positions: A Multicenter Study

OBJECTIVES

An intraoperative neural response telemetry-ratio (NRT-ratio) was established, which can provide information about the intraoperative intracochlear electrode array position for perimodiolar electrodes.

METHODS

In a retrospective controlled study in 2 tertiary referral centers, the electrophysiological data sets of 50 patients with measured intraoperative auto-NRTs and postoperative radiological examinations were evaluated. All patients were implanted with Nucleus slim straight electrodes. The NRT-ratio was calculated by dividing the average auto-NRT data from electrodes 16 to 18 with the average from electrodes 5 to 7. Using a flat panel tomography system or a computed tomography, the position of the electrode array was certified radiological.

RESULTS

Radiologically, 2 out of 50 patients were identified with an electrode translocated from the scala tympani into the scala vestibuli. The radiologically estimated electrodes indicating a scalar change showed a regular NRT-ratio but nonspecific NRT-level changes at the localization of translocation.

Vestibular end organ injury induced by middle ear treatment with ferric chloride in rats

Sensorineural hearing loss, ataxia, pyramidal signs, and vestibular deficits characterize superficial siderosis of the central nervous system. This study investigated changes in vestibular function, free radical formation, and phosphorylated cJun expression in the vestibular end organs after middle ear treatment with a ferric chloride (FeCl3) solution. A single injection of 70% FeCl3 solution into the unilateral middle ear cavity caused static vestibular symptoms, such as spontaneous nystagmus and head tilt. Asymmetric expression of c-Fos protein was observed in the bilateral vestibular nuclei and prepositus hypoglossal nuclei within 6 h after injection. Histopathologic examinations revealed partial hair cell loss, degeneration of the supporting stroma, and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells in the neuroepithelial layer of the crista ampullaris in FeCl3-treated animals. 5-(And-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate, acetyl ester and diaminofluorescein–2 diacetate fluorescence and immunoreactivity for nitrotyrosine increased markedly in the sensory neuroepithelial layer and nerve bundles of the crista ampullaris after 2 h. Strong immunoreactivity for phospho-cJun and cJun was observed in the type I hair cells of the crista ampullaris 120 h after injection. Thus, a single short-term treatment with a high concentration of FeCl3 in the unilateral middle ear cavity can induce activation of intracellular signals for cJun protein and oxidative stress through the formation of reactive oxygen species and nitric oxide in vestibular sensory receptors, resulting in vestibular dysfunction. These results suggest that activation of intracellular signals for cJun protein and oxidative stress may be a key component of the pathogenesis of vestibular deficits in patients with superficial siderosis.

Cochlear Implantation in Patients With Superficial Siderosis: Seven Cases and Systematic Review of the Literature

OBJECTIVE

To date, there have been less than 30 cases of cochlear implantation (CI) in patients with superficial siderosis (SS) reported in the literature. The primary objective of the current study is to evaluate CI outcomes in six additional patients (seven ears) with SS and sensorineural hearing loss (SNHL) and to perform a systematic review of the literature.

STUDY DESIGN

Case series and systematic review of the literature.

SETTING

Two tertiary academic CI centers.

PATIENTS

All patients with SS who underwent CI between 2007 and 2014.

INTERVENTION(S)

Cochlear implantation.

MAIN OUTCOME MEASURES

Pre- and post-implantation speech perception scores and durability of benefit.

RESULTS

A total of seven ears (four males; median age 52 yr) with SS and SNHL met inclusion criteria. All patients developed progressive bilateral SNHL that was no longer amenable to conventional hearing aids. Additional presenting symptoms included vestibulopathy (n = 4), cerebellar ataxia (n = 3), mild dementia (n = 1), and myelopathy (n = 1). All patients underwent uncomplicated CI, and intraoperative device telemetry revealed normal responses in all electrodes. The median postoperative auditory threshold average was 32.5 dB HL (range 16-36 dB) and the median postoperative CNC word score was 51% (range 46-64%). The median duration of follow-up was 15.5 months (range 3-64 mo). All patients demonstrated initial improvement in speech perception testing. Two patients had performance decline and worsening dementia resulting from progressive SS.

CONCLUSION

Cochlear implantation is a viable strategy for auditory rehabilitation in patients with SS and associated SNHL. Most individuals enjoy benefit from CI; however, patients should be counseled regarding the risks of performance decline with progressive SS.

Cochlear implantation is a therapeutic option for superficial siderosis patients with sensorineural hearing loss

Background:

Superficial siderosis is a rare disease that results from chronic bleeding in the subarachnoid space. Haemosiderin deposits throughout the subpial layers of the brain and spinal cord lead to progressive sensorineural hearing loss, which is seen in 95 per cent of patients with superficial siderosis. The impact of cochlear implantation on the quality of life of superficial siderosis patients is under debate.

Case report:

A 38-year-old male with superficial siderosis presented with bilateral progressive sensorineural hearing loss. The patient underwent cochlear implantation and his quality of life was improved as evaluated by the Abbreviated Profile of Hearing Aid Benefit inventory.

Conclusion:

The remarkable improvement in Abbreviated Profile of Hearing Aid Benefit scores shown in this study indicates that cochlear implantation leads to a better quality of life in superficial siderosis patients.

Evaluation of the Relationship between the NRT-Ratio, Cochlear Anatomy, and Insertions Depth of Perimodiolar Cochlear Implant Electrodes

The position of the cochlear implant electrode array within the scala tympani is essential for an optimal postoperative hearing benefit. If the electrode array changes in between the scalae intracochlearly (i.e., from scala tympani to scala vestibuli), a reduced auditory performance can be assumed. We established a neural response telemetry-ratio (NRT-ratio) which corresponds with the scalar position of the electrodes but shows within its limits a variability. The aim of this study was to determine if insertion depth angle or cochlea size influences the NRT-ratio. The intraoperative electrophysiological NRT data of 26 patients were evaluated. Using a flat panel tomography system, the position of the electrode array was evaluated radiologically. The insertion depth angle of the electrode, the cochlea size, and the NRT-ratio were calculated postoperatively. The radiological results were compared with the intraoperatively obtained electrophysiological data (NRT-ratio) and statistically evaluated. In all patients the NRT-ratio, the insertion depth angle, and the cochlea size could be determined. A significant correlation between insertional depth, cochlear size, and the NRT-ratio was not found. The NRT-ratio is a reliable electrophysiological tool to determine the scalar position of a perimodiolar electrode array. The NRT-ratio can be applied independent from insertion depth and cochlear size.

Electrophysiological Detection of Scalar-Changing Perimodiolar Cochlear Electrode Arrays: A Six-Month Follow-Up Study

The position of the cochlear electrode array within the scala tympani is essential for optimal hearing benefit. An intraoperative neural response telemetry ratio (NRT ratio; a threshold ratio of pairs of apical and basal electrodes) has been established, which can provide information about the intracochlear electrode array position. Out of a previous collective of 85 patients, the 6-month follow-up electrophysiological NRT data of 37 patients have been included in this study. Comparing the intraoperatively estimated NRT ratio with the 6-month follow-up NRT ratio, it remained unchanged intraindividually in 92% of cases. Within this group the NRT ratio and the intracochlear position of the electrode array matched in all cases. There were two newly occurring mismatches and one new match was observed. After a period of 6 months the NRT ratio remained unchanged in most cases and showed a good correlation with the intracochlear position of the electrode array.

Auditory neuropathy

Neural disorders of the auditory nerve are associated with particular disorders of auditory perceptions dependent on processing of acoustic temporal cues. These include: (1) speech perception; (2) localizing a sound's origin in space; and (3) identifying sounds in background noise. Auditory neuropathy (AN) is a consequence of: (1) presynaptic disorders affecting inner hair cell ribbon synapses; (2) postsynaptic disorders of auditory nerve dendrites; and (3) postsynaptic disorders of auditory nerve axons. The etiologies of these disorders are diverse, similar to other cranial or peripheral neuropathies. The pathologies cause attenuated and dyssynchronous auditory nerve discharges. Therapies and management of patients with AN are reviewed.

Vestibular function in superficial siderosis

BACKGROUND

Superficial siderosis (SS) is caused by repeated or continuous bleeding into the subarachnoid space that results in iron from hemoglobin (hemosiderin) being deposited on the surface of the brain. Clinically, the condition is characterized by sensorineural deafness, ataxia, and pyramidal signs. However the mechanism of peripheral vestibular disturbance was not revealed. We show the vestibular function of SS patients, and shed light on saccule-inferior vestibular nerve.

METHODS

Over the past 9 years, 5 patients were definitively diagnosed with SS by MRI in our department. These patients were subjected to balance testing.

RESULTS

Vestibular evoked myogenic potential (VEMP) was observed in patients who had suffered from SS for a short period but tended to be diminished or absent in patients who had suffered from the condition for a longer period.

CONCLUSIONS

These findings in SS patients suggest that saccule-inferior vestibular function is maintained at early stages of the disorder. Our study may help to clarify the mechanism of SS.

Programming peculiarities in two cochlear implant users with superficial siderosis of the central nervous system

OBJECTIVE

To report the audiological outcomes of cochlear implantation in two patients with severe to profound sensorineural hearing loss secondary to superficial siderosis of the CNS and discuss some programming peculiarities that were found in these cases.

METHOD

Retrospective review. Data concerning clinical presentation, diagnosis and audiological assessment pre- and post-implantation were collected of two patients with superficial siderosis of the CNS.

RESULTS

Both patients showed good hearing thresholds but variable speech perception outcomes. One patient did not achieve open-set speech recognition, but the other achieved 70% speech recognition in quiet. Electrical compound action potentials could not be elicited in either patient. Map parameters showed the need for increased charge. Electrode impedances showed high longitudinal variability.

CONCLUSION

The implants were fairly beneficial in restoring hearing and improving communication abilities although many reprogramming sessions have been required. The hurdle in programming was the need of frequent adjustments due to the physiologic variations in electrical discharges and neural conduction, besides the changes in the impedances. Patients diagnosed with superficial siderosis may achieve limited results in speech perception scores due to both cochlear and retrocochlear reasons. Careful counseling about the results must be given to the patients and their families before the cochlear implantation indication.