||Presbycusis is more complicated than simply a failure of cochlear function due to aging. There is also frequently evidence of significant dysfunction in the central auditory connections, the auditory cortex and the central cochlear nuclei (central presbycusis).
With primary central presbycusis there is a disproportionate loss of discrimination and central integrative and synthesizing processes, which is more severe than the hearing loss for pure tones alone would cause. This loss in central auditory competence can be demonstrated by simultaneous binaural challenges, and frequency and temporal distortion tests. The development of central presbycusis is related to age, although there is a significant variability between individuals from similar age groups.
The histologic changes associated with central presbycusis consist of both central and peripheral neural degeneration. There is a decrease in both the volume and the number of cells in the ventral and dorsal cochlear nuclei. Peripherally there is a loss of the cochlear neurons throughout the entire cochlea, which is consistently more severe in the basal turn.