Examples of microscopic changes seen in this condition are hair cell degeneration of the cochlea and giant stereociliary degeneration. There are four pathological phenotypes of<unk> : * Sensory: characterised by degeneration of the organ of Corti, the sensory organ for hearing. Located within the scala media, it contains hair cells with stereocilia, which extend to the tectorial membrane. The organ's outer hair cells play a significant role in the amplification of sound and is extremely sensitive to external and internal factors. If the outer hair cells are damaged, they do not regenerate. This results in a loss of sensitivity of hearing, as well as an abnormal perceived loudness in the aspect of the tonotopic spectrum that the damaged cells serve. * Neural: characterised by degeneration of cells of the spiral ganglion. * Strial/metabolic: characterised by atrophy of stria vascularis in all turns of cochlea. Located in the lateral wall of the cochlea, the stria vascularis contains sodium-potassium-ATPase pumps that are responsible for producing the endolymph resting potential. As individuals age, a loss of capillaries leads to the endolymphatic potential becoming harder to maintain, which brings a decrease in cochlear potential. * Cochlear conductive: due to stiffening of the basilar membrane thus affecting its movement. This type of pathology has not been verified as contributing to<unk> . In addition there are two other types: * Mixed * Indeterminate The shape of the audiogram categorizes abrupt high-frequency loss (sensory phenotype) or flat loss (strial phenotype). The mainstay of SNHL is strial, with only about 5% of cases being sensory. This type of<unk>  is manifested by a low-frequency hearing loss, with unimpaired speech recognition. Classically, audiograms in neural<unk>  show a moderate downward slope into higher frequencies with a gradual worsening over time. A severe loss in speech discrimination is often described, out of proportion to the threshold loss, making amplification difficult due to poor comprehension. The audiogram associated with sensory<unk>  is thought to show a sharply sloping high-frequency loss extending beyond the speech frequency range, and clinical evaluation reveals a slow, symmetric, and bilateral progression of hearing loss.
Presbycusis
Autistica
Alogia
Pyromania
Pleurothotonus
Lonomia
Pellagra
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