It is a progressive and irreversible bilateral symmetrical age-related sensorineural hearing loss resulting from degeneration of the cochlea or associated structures of the inner ear or auditory nerves.

Many vertebrates such as fish, birds and amphibians do not experience presbycusis in old age as they are able to regenerate their cochlear sensory cells, whereas mammals including humans have genetically lost this regenerative ability.

The ISO standard 7029 shows expected threshold changes due purely to age for carefully screened populations (i.e. excluding those with ear disease, noise exposure etc.

One early consequence is that even young adults may lose the ability to hear very high frequency tones above 15 or 16 kHz.

The effects of age can be exacerbated by exposure to environmental noise, whether at work or in leisure time (shooting, music, etc.).

[7] Older adults with presbycusis often exhibit associated symptoms of social isolation, depression, anxiety, frailty and cognitive decline.

[11] Other risk factors include preexisting noise-induced hearing loss and exposure to ototoxic medications.

Classically, audiograms in neural presbycusis show a moderate downward slope into higher frequencies with a gradual worsening over time.

Pure-tone audiometry for air conduction thresholds at 250, 500, 1000, 2000, 4000, 6000 and 8000 Hz is traditionally used to classify the degree of hearing loss in each ear.

As part of differential diagnosis, an MRI scan may be done to check for vascular anomalies, tumors, and structural problems like enlarged mastoids.

The inside component, the actual implant, has a coil to receive signals, electronics, and an array of electrodes which is placed into the cochlea, which stimulate the cochlear nerve.

The electrodes of the implant are designed to stimulate the array of nerve fibers that previously responded to different frequencies accurately.

These aids work by directly vibrating the ossicles, and are cosmetically favorable due to their hidden nature.

Many vertebrates such as fish, birds and amphibians do not experience presbycusis in old age as they are able to regenerate their cochlear sensory cells, whereas mammals including humans have genetically lost this ability.

[18] A number of laboratories worldwide are conducting comparative studies of birds and mammals that aim to find the differences in regenerative capacity, with a view to developing new treatments for human hearing problems.