This review aimed to present some of the leading causes of ear disease and hearing loss globally, and to identify their impact at both an individual and societal level.

Evoked potential thresholds using the 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) were recorded at 500 Hz and 4000 Hz test frequencies in 36 subjects with normal acuity, and 30 subjects with sensorineural hearing loss. ASSR threshold sensation levels (SLs) were lower in ears with greater degrees of hearing loss, and for the 500 Hz stimulus. Mean SLs (maximum duration of a single recording: 89 seconds) were as follows at 500 Hz and 4000 Hz respectively: normal hearing group, 16.9+/-10.3 dB and 42.4+/-14.4 dB; mild-moderate group, 10.6+/-8.8 dB and 23.8+/-8.1 dB; severe-profound group, 10.0+/-13.2 dB and 21.5+/-18.9 dB. CAEP SLs showed no change with hearing level and CAEP/behavioural differences were similar at each test frequency. Mean SLs for CAEP threshold (single recording duration: 84 seconds) at 500 Hz and 4000 Hz respectively were: normal hearing group, 10.3+/-6.4 dB and 11.5+/-3.8 dB; mild-moderate group, 8.4+/-7.4 dB and 13.2+/-12.4 dB; severe-profound group, 11.0+/-6.6 dB and 15.9+/-16.4 dB. The results of this study suggest that while both 40 Hz ASSR and CAEP can reflect the behavioural audiogram, CAEPs may provide a more reliable estimate of hearing in awake adults.

Results show a relationship between early conductive hearing loss and listening deficits that persist once hearing has returned to normal. Results also suggest that the two binaural interaction tasks (LiSN-S and MLD) may be measuring binaural processing at different levels. Findings highlight the need for a screening measure of functional listening ability in children with a history of early otitis media.

The aims of this study are to investigate whether auditory dysfunction is part of the spectrum of neurological abnormalities associated with Leber's hereditary optic neuropathy (LHON) and to determine the perceptual consequences of auditory neuropathy (AN) in affected listeners. Forty-eight subjects confirmed by genetic testing as having one of four mitochondrial mutations associated with LHON (mt11778, mtDNA14484, mtDNA14482 and mtDNA3460) participated. Thirty-two of these had lost vision, and 16 were asymptomatic at the point of data collection. While the majority of individuals showed normal sound detection, >25% (of both symptomatic and asymptomatic participants) showed electrophysiological evidence of AN with either absent or severely delayed auditory brainstem potentials. Abnormalities were observed for each of the mutations, but subjects with the mtDNA11778 type were the most affected. Auditory perception was also abnormal in both symptomatic and asymptomatic subjects, with >20% of cases showing impaired detection of auditory temporal (timing) cues and >30% showing abnormal speech perception both in quiet and in the presence of background noise. The findings of this study indicate that a relatively high proportion of individuals with the LHON genetic profile may suffer functional hearing difficulties due to neural abnormality in the central auditory pathways.