Auditory brainstem implantation (ABI) in children without neurofibromatosis type II (NF2): communication performance and safety after 24 months of use.

Objectives: To assess the safety and communication performance of auditory brainstem implant (ABI) provision in children who were contraindicated for cochlear implantation and do not have neurofibromatosis type II (NF2).Methods: Communication performance was assessed via a battery of tests up to 24 months after first fitting. Safety was assessed intra-operatively and via post-operative adverse event reports.Results: Ten children participated in the study. The mean communication skills on all 8 tests for which inferential statistics were possible increased significantly from pre-operatively to 12 months and either again increased significantly or remained stable from 12 to 24 months. Communication development was variable: some children achieved high scores while others did not. Two serious adverse events that were device or procedure-related were reported and successfully resolved.Discussion: ABI provision in this population group was safe. Participants' auditory abilities were significantly better after 24 months of ABI use than at pre-implantation. Development was slower than that of children with a cochlear implant but may continue progressing after 24 months of use.Conclusion: ABI provision and use is safe and allows significant auditory development in children without NF2 who are contradicted for cochlear implantation.

Effects of lifetime noise exposure on the middle-age human auditory brainstem response, tinnitus and speech-in-noise intelligibility.

Recent animal studies have shown that the synapses between inner hair cells and the dendrites of the spiral ganglion cells they innervate are the elements in the cochlea most vulnerable to excessive noise exposure. Particularly in rodents, several studies have concluded that exposure to high level octave-band noise for 2 h leads to an irreversible loss of around 50% of synaptic ribbons, leaving audiometric hearing thresholds unaltered. Cochlear synaptopathy following noise exposure is hypothesized to degrade the neural encoding of sounds at the subcortical level, which would help explain certain listening-in-noise difficulties reported by some subjects with otherwise 'normal' hearing. In response to this peripheral damage, increased gain of central stages of the auditory system has been observed across several species of mammals, particularly in association with tinnitus. The auditory brainstem response (ABR) wave I amplitude and waves I-V amplitude ratio have been suggested as non-invasive indicators of cochlear synaptopathy and central gain activation respectively, but the evidence for these hearing disorders in humans is inconclusive. In this study, we evaluated the influence of lifetime noise exposure (LNE) on the human ABR and on speech-in-noise intelligibility performance in a large cohort of adults aged 29 to 55. Despite large inter-subject variability, results showed a moderate, but statistically significant, negative correlation between the ABR wave I amplitude and LNE, consistent with cochlear synaptopathy. The results also showed (a) that central gain mechanisms observed in animal studies might also occur in humans, in which higher stages of the auditory pathway appear to compensate for reduced input from the cochlea; (b) that tinnitus was associated with activation of central gain mechanisms; (c) that relevant cognitive and subcortical factors influence speech-in-noise intelligibility, in particular, longer ABR waves I-V interpeak latencies were associated with poorer performance in understanding speech in noise when central gain mechanisms were active; and (d) absence of a significant relationship between LNE and tinnitus, central gain activation or speech-in-noise performance. Although this study supports the possible existence of cochlear synaptopathy in humans, the great degree of variability, the lack of uniformity in central gain activation and the significant involvement of attention in speech-in-noise performance suggests that noise-induced cochlear synaptopathy is, at most, one of several factors that play a role in humans' speech-in-noise performance.

Effects of cochlear synaptopathy on middle-ear muscle reflexes in unanesthetized mice.

Cochlear synaptopathy, i.e. the loss of auditory-nerve connections with cochlear hair cells, is seen in aging, noise damage, and other types of acquired sensorineural hearing loss. Because the subset of auditory-nerve fibers with high thresholds and low spontaneous rates (SRs) is disproportionately affected, audiometric thresholds are relatively insensitive to this primary neural degeneration. Although suprathreshold amplitudes of wave I of the auditory brainstem response (ABR) are attenuated in synaptopathic mice, there is not yet a robust diagnostic in humans. The middle-ear muscle reflex (MEMR) might be a sensitive metric (Valero et al., 2016), because low-SR fibers may be important drivers of the MEMR (Liberman and Kiang, 1984; Kobler et al., 1992). Here, to test the hypothesis that narrowband reflex elicitors can identify synaptopathic cochlear regions, we measured reflex growth functions in unanesthetized mice with varying degrees of noise-induced synaptopathy and in unexposed controls. To separate effects of the MEMR from those of the medial olivocochlear reflex, the other sound-evoked cochlear feedback loop, we used a mutant mouse strain with deletion of the acetylcholine receptor required for olivocochlear function. We demonstrate that the MEMR is normal when activated from non-synaptopathic cochlear regions, is greatly weakened in synaptopathic regions, and is a more sensitive indicator of moderate synaptopathy than the suprathreshold amplitude of ABR wave I.

Noise-induced cochlear synaptopathy in rhesus monkeys (Macaca mulatta).

Cochlear synaptopathy can result from various insults, including acoustic trauma, aging, ototoxicity, or chronic conductive hearing loss. For example, moderate noise exposure in mice can destroy up to ∼50% of synapses between auditory nerve fibers (ANFs) and inner hair cells (IHCs) without affecting outer hair cells (OHCs) or thresholds, because the synaptopathy occurs first in high-threshold ANFs. However, the fiber loss likely impairs temporal processing and hearing-in-noise, a classic complaint of those with sensorineural hearing loss. Non-human primates appear to be less vulnerable to noise-induced hair-cell loss than rodents, but their susceptibility to synaptopathy has not been studied. Because establishing a non-human primate model may be important in the development of diagnostics and therapeutics, we examined cochlear innervation and the damaging effects of acoustic overexposure in young adult rhesus macaques. Anesthetized animals were exposed bilaterally to narrow-band noise centered at 2 kHz at various sound-pressure levels for 4 h. Cochlear function was assayed for up to 8 weeks following exposure via auditory brainstem responses (ABRs) and otoacoustic emissions (OAEs). A moderate loss of synaptic connections (mean of 12-27% in the basal half of the cochlea) followed temporary threshold shifts (TTS), despite minimal hair-cell loss. A dramatic loss of synapses (mean of 50-75% in the basal half of the cochlea) was seen on IHCs surviving noise exposures that produced permanent threshold shifts (PTS) and widespread hair-cell loss. Higher noise levels were required to produce PTS in macaques compared to rodents, suggesting that primates are less vulnerable to hair-cell loss. However, the phenomenon of noise-induced cochlear synaptopathy in primates is similar to that seen in rodents.

[The peculiar features of the psychosomatic status in the patients presenting with the spondylogenic and cochleovestibular disorders]. / Osobennosti psikhosomaticheskogo statusa u bol'nykh s vertebrogennymi kokhleovestibuliarnymi narusheniiami.

The objective of the present study was to elucidate the peculiar features of the psychosomatic status in the patients with chronic vertebrogenic and cochleovestibular disorders The psychosomatic status was evaluated in 117 patients at the age from 21 to 65 years presenting with these conditions using the psychometric tests based on the STAI questionnaire (the state-trait anxiety inventory) adapted for the determination of the level of reactive and personal anxiety. It was shown that the vestibular disorders, tympanophonia, and hearing impairment have a negative influence on the psychogenic status of the patients suffering from cochleovestibulopathy. As many as 92.3% of the patients were characterized by the high or moderately high level of reactive and personal anxiety. The depressive conditions of various severity were diagnosed in 29.1% of the patients. The correction of postural muscular disbalance made it possible to achieve the well apparent reduction of the manifestations of reactive anxiety without prescription of the pharmacotherapeutic treatment and thereby to increase the effectiveness of the management of the patients presenting with the vertebrogenic and cochleovestibular disorders.

[Psychosomatic status of patients with cochleovestibular disorders. Correction methods].

Psychosomatic status was studied in 106 patients aged 18-65 years with acute and chronic cochleovestibular disorders. Hearing problems, noise in the ears and vestibular disorders have a negative psychogenic effect in patients with cochleovestibulopathy. The majority of the patients need psychological and psychopharmacological care to relieve anxiety and form adequate attitude to the disease. Correction of psychosomatic disorders raises efficacy of the treatment of cochleovestibular diseases.

An unusual disease presenting at an unusual age: Susac's syndrome.

Susac's syndrome is a rare disease of unknown aetiology affecting the small vessels of the retina, brain, and cochlea. We present the case of a 55-year-old female, the oldest patient yet described with the condition, and highlight the syndrome's clinical features.