Paul Avan

To propose a comprehensive audiological-vestibular test battery for characterising age-related hearing loss, enabling precise phenotyping of suprathreshold functional, physiological, and vestibular factors beyond audibility. To establish age- and audibility-dependent reference data in age-appropriate normal-hearing controls. Multidisciplinary consensus about test battery composition; Statistical analysis of centre effects to assess comparability of the test battery measured at two centres (Germany and France); Statistical analysis of age and pure-tone average (PTA) effects per test to identify potential covariates. n = 55 (39 German and 16 French) participants with hearing thresholds better than the age-dependent median of the PTA, aged 40 years or older. Due to negligible centre effects, all data were pooled across centres. Age- and PTA-dependent reference data were derived. Age and PTA effects were identified for some tests, especially for audiological-functional tests. No age effects were found for vestibular tests. Normative values for a clinically feasible, multidimensional audiological-vestibular test battery were provided, including several measures whose age and PTA dependencies were previously unclear. Age and PTA should be considered as covariates for interpretation of these tests in future applications such as, e.g. phenotype-genotype relations in specified cohorts. Extensive data documentation and verification are essential for cross-centre comparability.

Auditory Neuropathy Spectrum Disorders (ANSD) are best characterized by distorted patterns of auditory nerve activity despite preserved spectral analysis of sound in the cochlea. They should clinically translate into impaired speech recognition despite normal auditory sensitivity. While distinct pathophysiological mechanisms affecting auditory-nerve activity have been identified in animal models, current clinical speech tests cannot distinguish among them. Our working hypothesis is that current speech audiometry yields aggregate recognition scores that average across phoneme categories, obscuring mechanism-specific patterns instead of pinpointing distinctive signatures. Using computational modeling of auditory nerve responses, we tested four mechanism types, demonstrating that mechanism-specific encoding disruptions cascade into speech recognition failures. Brief consonants showed severe disruption while sustained vowels were preserved, with category-specific patterns differing across mechanisms. Models trained on ANSD-degraded signals developed compensation strategies that generalized to healthy signals, while the reverse failed completely: strategies exploiting slow temporal structure (sustained formants) generalize, while those requiring millisecond-scale timing do not. Noise training that benefited healthy models harmed ANSD models, explaining real-world listening difficulties. Phoneme-specific confusion patterns enable mechanism identification from behavioral testing alone, providing the missing diagnostic infrastructure for targeted intervention.

Auditory neuropathies affect the spiral ganglion neurons of the auditory nerve or their synapses with the sensory hair cells, distorting the sound information transmitted from the ear to the brain. Deciphering the underlying pathophysiological mechanisms remains challenging owing to the diversity of spiral ganglion neuron subtypes and associated central auditory circuits. An auditory neuropathy mechanism is unraveled by investigating the origin of auditory hyperexcitability in a mouse model for hereditary congenital deafness. Otogl encodes the large Otogelin‐like protein, which is related to secreted epithelial mucins and is implicated in the mechanical stimulation of cochlear outer hair cells. Heterozygous Otogl^+/− mutant mice display auditory hyperexcitability, highlighted by their susceptibility to audiogenic seizures induced by loud sounds. It is shown that Otogl is transiently expressed in a subpopulation of spiral ganglion neurons during cochlear development. Despite their apparently normal hearing, Otogl^+/− mice display poor activation of the spiral ganglion neurons processing loud sounds and an elevation of the activation threshold of the middle the ear muscle reflex that attenuates loud sounds. The findings reveal how a neuropathy affecting spiral ganglion neurons specialized in loud sound processing and associated with the middle the ear muscle reflex can manifest itself as auditory hyperexcitability.

Background: In order to better understand the pathophysiology of surgically induced hearing loss after vestibular schwannoma (VS) surgery, we postoperatively analyzed the hearing status in a series of patients where hearing was at least partially preserved. Methods: Hearing was assessed through tonal audiometry, speech discrimination score, maximum word recognition score (dissyllabic word lists—MaxIS), otoacoustic emissions (OAEs), and auditory brainstem response (ABR). The magnetic resonance imaging (MRI) tumor characterization was also noted. Results: In a series of 24 patients operated on for VS over 5 years, depending on the results of this triple hearing exploration, we could identify, after surgery, patients with either a myelin alteration or partial damage to the acoustic fibers, others with a likely partial cochlear ischemia, and some with partial cochlear nerve ischemia. One case with persisting OAEs and no preoperative ABR recovered hearing and ABR after surgery. Long follow-up (73 ± 57 months) revealed a mean hearing loss of 30 ± 20 dB with a drastic drop of MaxIS. MRI revealed only 25% of fundus invasion. Conclusion: a precise analysis of hearing function, not only with classic audiometry but also with ABR and OEAs, allows for a better understanding of hearing damage in VS surgery.

Médecine/sciences (M/S), revue internationale dans le domaine de la recherche biologique, médicale et en santé