The transtympanic promontory stimulation test in patients with auditory deprivation: correlations with electrical dynamics of cochlear implant and speech perception

Cochlear Implantation in Sporadic Vestibular Schwannoma and Neurofibromatosis Type II

Cochlear implantation offers significantly better hearing outcomes than auditory brainstem implantation in patients with vestibular schwannoma. Neither the primary treatment modality nor the cause of the tumor (neurofibromatosis type 2 related or sporadic) seems to have a significant effect on hearing outcome with cochlear implantation. Some uncertainty remains regarding long-term hearing outcomes; however, cochlear implantation in vestibular schwannoma serves to offer patients, with a functioning cochlear nerve, the probability of open set speech discrimination with a consequent positive impact on quality of life.

[Prospects for cochlear implantation in patients with auditory nerve dysplasia]

Auditory nerve dysplasia (AND) can encompass various conditions of the auditory nerve (AN), ranging from true aplasia to hypoplasia. The purpose of this review is to discuss the prospect of cochlear implantation (CI) and subsequent auditory speech rehabilitation for AN abnormality. Studies of different authors when working with this category of children, possible results and methods of diagnostics of the AN condition are presented.

Combined Electric acoustic stimulation in a patient with otitis media with antineutrophil cytoplasmic antibody-associated vasculitis

There are few reports of the treatment for severe hearing loss due to otitis media with antineutrophil cytoplasmic antibody-associated vasculitis (OMAAV) achieved by cochlear implantation (CI). Here, we have reported the case of a patient with severe bilateral sensorineural hearing loss with low-frequency residual hearing by OMAAV. CI was performed in her right ear based on the results of contrast-enhanced magnetic resonance imaging (CE-MRI) and promontory stimulation test (PST). The residual hearing in her right ear was preserved after CI and utilized for combined electric acoustic stimulation (EAS). The combined EAS was used for 3 years until the residual hearing became stabilized. However, the usable hearing in low frequency worsened gradually, and the fitting strategy of cochlear implant was changed from combined EAS to CI alone 4 years after CI. Even when the speech discrimination score with CI no longer exceeds 50 %, the patient continued using CI because of its advantages in maintaining the quality of life of the patient. The combined EAS was found to be a feasible option even in an OMAAV patient with residual hearing. CE-MRI and PST may thus be helpful in deciding the side of CI surgery in a patient with OMAAV.

Extracochlear Stimulation of Electrically Evoked Auditory Brainstem Responses (eABRs) Remains the Preferred Pre-implant Auditory Nerve Function Test in an Assessor-blinded Comparison

OBJECTIVE

Electrically evoked auditory brainstem responses (eABRs) can be recorded before cochlear implant (CI) surgery to verify auditory nerve function, and is particularly helpful in to assess the function of the auditory nerve in cases of auditory nerve hypoplasia. This is the first study to compare three preimplant eABRs recording techniques: 1) standard extracochlear, 2) novel intracochlear, and 3) conventional intracochlear with the CI.

STUDY DESIGN

A within-participants design was used where eABRs were sequentially measured during CI surgery using three methods with stimulation from: 1) an extracochlear electrode placed at the round window niche, 2) two different electrodes on a recently developed Intracochlear Test Array (ITA), and 3) two different electrodes on a CI electrode array.

SETTING

New adults implantees (n = 16) were recruited through the Manchester Auditory Implant Centre and eABR measurements were made in theater at the time of CI surgery.

PATIENTS

All participants met the clinical criteria for cochlear implantation. Only participants with radiologically normal auditory nerves were recruited to the study. All participants were surgically listed for either a MED-EL Synchrony implant or a Cochlear Nucleus Profile implant, per standard practice in the implant centre.

OUTCOME MEASURES

Primary outcome measures were: 1) charge (μC) required to elicit a threshold response, and 2) latencies (ms) in the threshold waveforms. Secondary outcome measures were: 1) morphologies of responses at suprathreshold stimulation levels and 2) wave V growth patterns.

RESULTS

eABRs were successfully measured from 15 participants. In terms of primary outcome measures, the charge required to elicit a response using the extracochlear electrode (median = 0.075 μC) was approximately six times larger than all other electrodes and the latency of wave V was approximately 0.5 ms longer when using the extracochlear electrode (mean = 5.1 ms). In terms of secondary outcomes, there were some minor quantitative differences in responses between extracochlear and intracochlear stimulation; in particular, ITA responses were highly variable in quality. The ITA responses were rated poor quality in 33% of recordings and in two instances did not allow for data collection. When not disrupted by open circuits, the median ITA response contained one more waveform than the median extracochlear response.

CONCLUSIONS

In this first study comparing intracochlear and extracochlear stimulation, the results show that both can be used to produce an eABR that is representative of the one elicited by the CI. In the majority of cases, extracochlear stimulation was the preferred approach for preimplant auditory nerve function testing because of consistency, recordings that could be analyzed, and because extracochlear placement of the electrode does not require a cochleostomy to insert an electrode.

Cochlear Implantation in Sporadic Vestibular Schwannoma: A Systematic Literature Review

Objective  This study was aimed to perform a systematic literature review by examining outcomes in patients with sporadic vestibular schwannoma (VS) undergoing ipsilateral cochlear implant (CI). Data Sources  PubMed-NCBI (National Center for Biotechnology Information) and Scopus databases were searched through October 2017. Study Selection  Studies reporting auditory outcomes for each patient when a CI was placed with an ipsilateral sporadic VS were included. Main Outcome Measures  Demographic variables, VS characteristics, preoperative hearing metrics, duration of deafness, CI type, approach to tumor resection, postoperative auditory outcomes, and postoperative tinnitus outcomes were reported for each eligible patient within studies. Each study was evaluated for quality and bias. Results  Fifteen studies and 45 patients met inclusion criteria. Mean speech discrimination score (SDS) improved from 30.0 to 56.4% after CI placement. The majority when reported had an improvement in tinnitus. Preoperative ipsilateral SDS was a negative predictor of postoperative SDS, while neither tumor resection status, tumor location, duration of deafness, ipsilateral pure tone average, nor timing of CI placement had a significant effect on patient outcome. Conclusions  Notwithstanding the challenges inherent with surveillance magnetic resonance imaging (MRI) in the setting of a cochlear implant magnet, select sporadic vestibular schwannoma patients can be considered for cochlear implantation.

Outcomes after cochlear implant provision in children with cochlear nerve hypoplasia or aplasia

INTRODUCTION

Cochlear nerve aplasia or hypoplasia is found in up to a half of patients with unilateral or bilateral hearing loss. There is an ongoing discussion regarding the indication of cochlear implants for hearing rehabilitation in cases with radiologically-defined aplasia or hypoplasia of the cochlear nerve in those patients, especially in children. At present there is conflicting evidence whether the audiological outcomes of those children with a CI are comparable to those of children with a CI and a radiologically-normal cochlear nerve. The primary aim of this study was to assess the audiological abilities before and after CI provision in children with cochlear nerve hypoplasia or aplasia. Additionally, we aimed to determine if audiological outcomes differed in children with aplasia from those with hypoplasia. Such data should be helpful in determining if CI provision is appropriate for such children.

METHODS

This retrospective study presents 7 children who were diagnosed with cochlear nerve aplasia or hypoplasia and received a CI. The pre- and postoperative audiological performance and the hearing and speech development of the children were examined.

RESULTS

4 children were unilateral CI users and 3 were bilateral CI users. Hearing reactions could be detected in all children. Already at first fitting, prompt responses and reactions to songs were observed. The aided thresholds in free field in children with hypoplasia were between 30 and 60 dB. Even in children with aplasia, the results in free field with CI averaged between 30 and 70 dB. Therefore the aided thresholds in children with hypoplasia and in children with aplasia of the CN are similar. It could be demonstrated that hearing reactions improve with the long term use of the implant. Improvement in general development could be observed in all children despite the very heterogeneous conditions and the accompanying handicaps.

CONCLUSION

The results of this study support the hypothesis that children with radiologically-defined CN hypoplasia or aplasia and detectable responses to electrical or acoustical stimuli can improve their sound detection thresholds and their awareness of sound when provided with a CI.

Utilization of Nerve Integrity Monitor for Promontory Stimulation Testing Prior to Cochlear Implant

OBJECTIVE

To demonstrate the feasibility of a nerve integrity monitor as a tool for promontory stimulation testing in patients with profound sensorineural hearing loss considering cochlear implantation.

PATIENTS

Adult patients considered for cochlear implantation with no auditory response on audiometric testing INTERVENTION:: Promontory stimulation testing using the nerve integrity monitor.

MAIN OUTCOME MEASURE

By using a facial nerve stimulator and the nerve integrity monitor, transtympanic promontory stimulation testing was performed to assess auditory nerve function and determine candidacy for cochlear implantation. Patients indicated if they heard the stimulus.

RESULTS

Of the four patients completing the promontory stimulation tests, three patients heard the stimulus and one patient did not hear the stimulus. Of the three patients with a positive stimulation test, two patients have a history of progressive profound sensorineural hearing loss and one patient had a history of severe blunt temporal bone trauma. Two of these patients proceeded with cochlear implantation. The patient who had a negative promontory stimulation test has a history of neurofibromatosis type 2.

CONCLUSION

The nerve integrity monitor is a convenient tool that can be used in the clinic setting to perform promontory stimulation tests and aid in determining cochlear implant candidates, specifically in those patients who require verification of auditory nerve function. This tool is a feasible and reasonable method for promontory stimulation testing.

The 'full-blown' MRI of sudden hearing loss: 3D FLAIR in a patient with bilateral metastases in the internal auditory canals

We report a case of a 57-year-old man with bilateral masses in the internal auditory canal. The peculiar findings at magnetic resonance imaging with tridimensional fluid-attenuated inversion recovery sequence combined with clinical data provided new insights into understanding the pathophysiology of the hearing loss.

Variability of word discrimination scores in clinical practice and consequences on their sensitivity to hearing loss

Speech perception scores are widely used to assess patient's functional hearing, yet most linguistic material used in these audiometric tests dates to before the availability of large computerized linguistic databases. In an ENT clinic population of 120 patients with median hearing loss of 43-dB HL, we quantified the variability and the sensitivity of speech perception scores to hearing loss, measured using disyllabic word lists, as a function of both the number of ten-word lists and type of scoring used (word, syllables or phonemes). The mean word recognition scores varied significantly across lists from 54 to 68%. The median of the variability of the word recognition score ranged from 30% for one ten-word list down to 20% for three ten-word lists. Syllabic and phonemic scores showed much less variability with standard deviations decreasing by 1.15 with the use of syllabic scores and by 1.45 with phonemic scores. The sensitivity of each list to hearing loss and distortions varied significantly. There was an increase in the minimum effect size that could be seen for syllabic scores compared to word scores, with no significant further improvement with phonemic scores. The use of at least two ten-word lists, quoted in syllables rather than in whole words, contributed to a large decrease in variability and an increase in sensitivity to hearing loss. However, those results emphasize the need of using updated linguistic material for clinical speech score assessments.

Central plasticity and dysfunction elicited by aural deprivation in the critical period

The acoustic signal is crucial for animals to obtain information from the surrounding environment. Like other sensory modalities, the central auditory system undergoes adaptive changes (i.e., plasticity) during the developmental stage as well as other stages of life. Owing to its plasticity, auditory centers may be susceptible to various factors, such as medical intervention, variation in ambient acoustic signals and lesion of the peripheral hearing organ. There are critical periods during which auditory centers are vulnerable to abnormal experiences. Particularly in the early postnatal development period, aural inputs are essential for functional maturity of auditory centers. An aural deprivation model, which can be achieved by attenuating or blocking the peripheral acoustic afferent input to the auditory center, is ideal for investigating plastic changes of auditory centers. Generally, auditory plasticity includes structural and functional changes, some of which can be irreversible. Aural deprivation can distort tonotopic maps, disrupt the binaural integration, reorganize the neural network and change the synaptic transmission in the primary auditory cortex or at lower levels of the auditory system. The regulation of specific gene expression and the modified signal pathway may be the deep molecular mechanism of these plastic changes. By studying this model, researchers may explore the pathogenesis of hearing loss and reveal plastic changes of the auditory cortex, facilitating the therapeutic advancement in patients with severe hearing loss. After summarizing developmental features of auditory centers in auditory deprived animals and discussing changes of central auditory remodeling in hearing loss patients, we aim at stressing the significant of an early and well-designed auditory training program for the hearing rehabilitation.

Successful cochlear implantation in two profoundly deafened patients with neurofibromatosis type 1: further evidence to support a cochlear site of lesion

OBJECTIVE

To investigate the usefulness of cochlear implantation and to examine the evidence for a cochlear or retrocochlear site of lesion for deafness in Neurofibromatosis Type 1 (NF1).

PATIENTS

Two profoundly deafened NF1 patients who underwent cochlear implantation.

INTERVENTIONS

Preoperative electrophysiologic and audiologic evaluation including pure-tone audiometry, auditory brainstem response, speech audiometry, otoacoustic emission, and promontory stimulation test. Intraoperative electrophysiologic tests were also performed.

MAIN OUTCOME MEASURES

Results of preoperative diagnostic workup. Cochlear implant performances were evaluated in the auditory-only condition in both closed-set and open-set formats.

RESULTS

Preoperative diagnostic assessment suggested cochlear impairment with preserved auditory pathway at the basis of the sensorineural hearing loss in both patients. Intraoperative electrically evoked auditory nerve and brainstem responses confirmed the integrity of the neural population all along the length of the cochlea. To date, with a follow-up of 2 and 10 years, both patients gained excellent open-set, auditory-only, speech understanding and were able to converse on the telephone without a code.

CONCLUSION

Cochlear impairment with preserved auditory pathways can be responsible for sensorineural hearing loss in NF1 patients. When their hearing deficit meets criteria for cochlear implantation, this type of auditory rehabilitation can restore social hearing in these patients while dramatically improving their quality of life.