Brainstem auditory pathway maturation in term neonates with congenital cytomegalovirus infection: a cohort study.

Congenital cytomegalovirus infection (cCMVi) is a leading cause of sensorineural hearing loss (SNHL) and developmental delay. Brainstem auditory evoked potentials (BAEPs) recording allows assessment of central auditory pathway maturation in neonates. We aimed to characterize the effect of cCMVi on the maturation of the brainstem auditory pathway in term neonates. We retrospectively reviewed medical records of neonates born with cCMVi in 2010-2018 and characterized their auditory pathway maturation using brainstem auditory-evoked potentials (BAEPs). We compared inter-peak latency differences (IPLDs) of the main BAEP components (I-V, I-III, and III-V) in terms of cCMVi patients and healthy controls and described their changes in cCMVi patients throughout the first year of life. Of 101 cCMVi patients, 57 (56.4%) were considered symptomatic, 6 (5.9%) were small for gestational age, 6 (5.9%) had microcephaly, 4 (4%) had thrombocytopenia, 5 (6.6%) had hepatitis, 2 (2.1%) had retinitis, 47 (49.5%) had typical abnormalities on head ultrasound, 9 (8.9%) developed SNHL, and 34 (59.6%) received antiviral therapy. No significant difference was found between IPLDs of full-term cCMVi patients compared to controls throughout the entire auditory pathway (I-III, III-V, and I-V IPLDs), for both ears (p > 0.05). On serial BAEP examinations, cCMVi patients presented decreased IPLDs throughout the first year of life (p < 0.05 of compared 1st, 2nd, and 3rd BAEPs in both ears).   Conclusions: Intrauterine cytomegalovirus infection does not affect the auditory brainstem maturation process in term neonates. Our findings support previous studies noting the normal neurodevelopmental outcome of asymptomatic cCMVi patients, suggesting antiviral treatment is not warranted in these cases. What is Known: • cCMVi is a leading cause of developmental delay and hearing loss. Treatment is recommended for patients with symptomatic diseases who are at significant risk of long-term sequelae. • It is unknown whether cCMVi affects the central nervous system maturation process. What is New: • We performed a neurophysiological evaluation of brainstem conduction by recording the BAEPs. We found that cCMVi has no significant impact on central conduction times along the auditory pathways in the brainstem at birth nor changes the neuronal maturation process during the first year of life. • Our findings suggest that cCMVi does not universally affect central nervous system maturation, supporting a highly selective approach when considering the benefits of antiviral therapy.

Infrafloccular approach effectively prevents hearing complication in microvascular decompression surgery for hemifacial spasm.

OBJECTIVE: The infrafloccular approach in microvascular decompression (MVD) surgery for hemifacial spasm (HFS) was investigated for the prevention of hearing complications. METHODS: Retrospective analysis of 136 patients who underwent MVD for HFS in 2019. The infrafloccular approach for MVD was adopted to resolve the symptom and protect hearing function. Postoperative hearing function was evaluated subjectively and objectively within 30 postoperative days, and later mainly subjectively. Postoperative condition of mastoid air cells based on the CT scan of the following day was also recorded. RESULTS: No final postoperative subjective hearing impairment was found in all patients. Mastoid air cells were opened in 105 patients, and subjective hearing impairment was recorded in 57 patients within 30 postoperative days, but all improved later. Increases in thresholds of greater than 10 dB in air conduction were observed in 28 patients, including 26 of transient conductive hearing loss (increases in the threshold of less than or equal to 10 dB). The other 2 patients with increases in the threshold of greater than 10 dB in both air and bone conduction had improvement confirmed by later audiometry. CONCLUSIONS: Infrafloccular approach in MVD for HFS provides a good hearing outcome. Inclusion of postoperative hearing conditions in the later period is ideal for a precise hearing evaluation.

Drug-induced hearing loss: Listening to the latest advances.

Sensorineural hearing loss (SNHL) is the most common type of hearing loss. Causes include degenerative changes in the sensory hair cells, their synapses and/or the cochlear nerve. As human inner ear hair cells have no capacity for regeneration, their destruction is irreversible and leads to permanent hearing loss. SNHL can be genetically inherited or acquired through ageing, exposure to noise or ototoxic drugs. Ototoxicity generally refers to damage to the structures and functions of the inner ear following exposure to specific drugs. Ototoxicity can be multifactorial, causing damage to cochlear hair cells or cells with homeostatic functions that modulate cochlear hair cell function. Clinical strategies to limit ototoxicity include identifying patients at risk, monitoring drug concentrations, performing serial hearing assessments and switching to less ototoxic therapy. This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, using the PubMed® database. The search terms "ototoxicity", "hearing loss" and "drugs" were combined. We included studies published between September 2013 and June 2023, and focused on medicines and drugs used in hospitals. The review highlighted a number of articles reporting the main drug classes potentially involved: namely, immunosuppressants, antimalarials, vaccines, antibiotics, antineoplastic agents, diuretics, nonsteroidal anti-inflammatory drugs and analgesics. The presumed ototoxic mechanisms were described, together with the therapeutic and preventive options developed over the last ten years.

Exploring the origins of decreased sound tolerance in tinnitus patients.

This study aimed to confirm the characteristics of auditory function alterations in tinnitus patients with concomitant decreased sound tolerance (ST) and provide insights for developing tailored therapeutic approaches. A retrospective analysis was conducted on patient records from a tertiary university hospital's tinnitus clinic between March 2020 and June 2023. Demographic attributes and audiological profiles were reviewed. Patients were categorized into Group 1 if loudness discomfort level test outcomes were 77 dB or below, measured using an average of frequencies from 250 Hz to 8 kHz. The remaining patients were allocated to Group 2. Among the 434 tinnitus patients, 115 (26.5%) demonstrated decreased ST and were classified as Group 1. This group exhibited higher DPOAE amplitudes (p < 0.001), shortened latency, and decreased threshold of ABR wave V bilaterally (p < 0.05). No significant disparities were observed in gender, age, tinnitus handicap inventory, visual analog scale, and pure-tone audiometry results except subjective hyperacusis. Binary logistic regression analysis utilizing the forward conditional method revealed that the difference between groups was independently linked to DPOAE response at 7,277 Hz on the left side [B = 0.093, p < 0.001, EXP(B) = 1.07, 95% CI = 1.044-1.153]. Increased DPOAE amplitude and shorter and decreased ABR wave V in tinnitus patients with decreased ST might suggest a possible association with lesions in or around the superior olivary complex or higher central auditory pathway, potentially linked to the inhibition of medial olivocochlear efferents.

Auditory Brainstem Response to Paired Click Stimulation as an Indicator of Peripheral Synaptic Health in Noise-Induced Cochlear Synaptopathy.

INTRODUCTION: A defect in the cochlear afferent synapse between the inner hair cells and spiral ganglion neurons, after noise exposure, without changes in the hearing threshold has been reported. Animal studies on auditory evoked potentials demonstrated changes in the auditory brainstem response (ABR) measurements of peak I amplitude and the loss of synapses, which affect the temporal resolution of complex sounds. Human studies of auditory evoked potential have reported ambiguous results regarding the relationship between peak I amplitude and noise exposure. Paired click stimuli have been used to investigate the temporal processing abilities of humans and animals. In this study, we investigated the utility of measuring auditory evoked potentials in response to paired click stimuli to assess the temporal processing function of ribbon synapses in noise-induced cochlear synaptopathy. MATERIALS AND METHODS: Twenty-two Sprague Dawley rats were used in this study, and synaptopathy was induced by narrow-band noise exposure (16 kHz with 1 kHz bandwidth, 105 dB sound pressure level for 2 h). ABRs to tone and paired click stimuli were measured before and 1, 3, 7, and 14 days after noise exposure. For histological analyses, hair cells and ribbon synapses were immunostained and the synapses quantified. The relationships among ABR peak I amplitude, number of synapses, and ABR to paired click stimuli were examined. RESULTS: Our results showed that ABR thresholds increase 1 day after noise exposure but fully recover to baseline levels after 14 days. Further, we demonstrated test frequency-dependent decreases in peak I amplitude and the number of synapses after noise exposure. These decreases were statistically significant at frequencies of 16 and 32 kHz. However, the ABR recovery threshold to paired click stimuli increased, which represent deterioration in the ability of temporal auditory processing. Our results indicate that the ABR recovery threshold is highly correlated with ABR peak I amplitude after noise exposure. We also established a direct correlation between the ABR recovery threshold and histological findings. CONCLUSION: The result from this study suggests that in animal studies, the ABR to paired click stimuli along with peak I amplitude has potential as an assessment tool for hidden hearing loss.