Auditory neuropathy in Brown-Vialetto-Van Laere syndrome due to riboflavin transporter RFVT2 deficiency.

AIM: Mutations in the genes encoding the riboflavin transporters RFVT2 and RFVT3 have been identified in Brown-Vialetto-Van Laere syndrome, a neurodegenerative disorder characterized by hearing loss and pontobulbar palsy. Treatment with riboflavin has been shown to benefit individuals with the phenotype of RFVT2 deficiency. Understanding the characteristics of hearing loss in riboflavin transporter deficiency would enable early diagnosis and therapy. METHOD: We performed hearing assessments in seven children (from four families) with RFVT2 deficiency and reviewed results from previous assessments. Assessments were repeated after 12 months and 24 months of riboflavin therapy and after cochlear implantation in one individual. RESULTS: Hearing loss in these individuals was due to auditory neuropathy spectrum disorder (ANSD). Hearing loss was identified between 3 years and 8 years of age and progressed rapidly. Hearing aids were not beneficial. Riboflavin therapy resulted in improvement of hearing thresholds during the first year of treatment in those with recent-onset hearing loss. Cochlear implantation resulted in a significant improvement in speech perception in one individual. INTERPRETATION: Riboflavin transporter deficiency should be considered in all children presenting with an auditory neuropathy. Speech perception in children with ANSD due to RFVT2 deficiency may be significantly improved by cochlear implantation.

Deafness in cochlear and auditory nerve disorders.

Sensorineural hearing loss is the most common type of hearing impairment worldwide. It arises as a consequence of damage to the cochlea or auditory nerve, and several structures are often affected simultaneously. There are many causes, including genetic mutations affecting the structures of the inner ear, and environmental insults such as noise, ototoxic substances, and hypoxia. The prevalence increases dramatically with age. Clinical diagnosis is most commonly accomplished by measuring detection thresholds and comparing these to normative values to determine the degree of hearing loss. In addition to causing insensitivity to weak sounds, sensorineural hearing loss has a number of adverse perceptual consequences, including loudness recruitment, poor perception of pitch and auditory space, and difficulty understanding speech, particularly in the presence of background noise. The condition is usually incurable; treatment focuses on restoring the audibility of sounds made inaudible by hearing loss using either hearing aids or cochlear implants.

Cervical vestibular evoked myogenic potentials and caloric test results in individuals with auditory neuropathy spectrum disorders.

Auditory neuropathy spectrum disorder is a type of hearing loss where outer hair cell function are normal (as evidenced by the preservation of OAEs and cochlear microphonics), whereas auditory nerve functions are abnormal (as evidenced by abnormal auditory brainstem evoked potentials beginning with wave I of the ABR) and acoustic reflexes to ipsilateral and contralateral tones are absent. It is likely that in cases with auditory neuropathy spectrum disorder not only the cochlear nerve, but also the vestibular nerves might get involved. The present study was conducted with an aim of finding out the inferior and superior vestibular nerve involvement through cervical vestibular evoked myogenic potentials and Caloric test results respectively in individuals with Auditory Neuropathy Spectrum Disorders. Total 26 participants who fulfilled the criteria of auditory neuropathy spectrum disorder participated for the study. Vestibular evoked myogenic potentials results showed absence of responses from most of the subjects also caloric responses showed bilateral hypofunctional responses in most of the participants, which is suggestive of involvement of both the inferior as well as superior vestibular nerve in individuals with auditory neuropathy spectrum disorders. Additionally there was no association between the pattern and degree of hearing loss to caloric test results and vestibular evoked myogenic potentials results findings.

Auditory evoked magnetic fields in patients with absent brainstem responses due to auditory neuropathy with optic atrophy.

OBJECTIVE: To examine whether auditory evoked fields (AEFs) can be used to objectively evaluate hearing in patients with absent auditory brainstem responses (ABRs) due to auditory neuropathy. METHODS: Subjects were 3 patients with auditory neuropathy, 1 male aged 29 years and 2 females aged 18 and 27 years, with absence of click evoked ABRs for bilateral ear stimuli at a level of 105 dB nHL. All patients also had optic atrophy. AEFs were measured with a helmet-shaped magnetoencephalography system for 2.0 kHz tone bursts of 60 ms duration to the unilateral ear. RESULTS: Bihemispherical AEF responses were clearly recorded in all three patients for either left or right ear stimulus. Although the latencies of N100m were severely prolonged and amplitudes were considerably decreased compared to the normal range of N100m responses in our facilities, N100m latency of AEF was shorter in the contralateral hemisphere to the stimulated ear, as usually found in normal subjects, despite the abnormal delay in N100m latency in all conditions. CONCLUSIONS: Presence and abnormality of auditory cortical responses can be evaluated by AEFs in patients with auditory neuropathy even under null responses in ABRs. SIGNIFICANCE: AEFs are useful to evaluate residual hearing in patients with auditory neuropathy.

Cortical motion deafness.

The extent to which the auditory system, like the visual system, processes spatial stimulus characteristics such as location and motion in separate specialized neuronal modules or in one homogeneously distributed network is unresolved. Here we present a patient with a selective deficit for the perception and discrimination of auditory motion following resection of the right anterior temporal lobe and the right posterior superior temporal gyrus (STG). Analysis of stimulus identity and location within the auditory scene remained intact. In addition, intracranial auditory evoked potentials, recorded preoperatively, revealed motion-specific responses selectively over the resected right posterior STG, and electrical cortical stimulation of this region was experienced by the patient as incoming moving sounds. Collectively, these data present a patient with cortical motion deafness, providing evidence that cortical processing of auditory motion is performed in a specialized module within the posterior STG.