Hearing is the process by which the ear transforms sound vibrations from the external environment into nerve impulses that are conveyed to the brain where they are interpreted as sound.
Hearing loss is described by which portion(s) of the ear is involved: conductive, sensorineural & mixed.
• Conductive hearing loss – occurs when sound is not conducted efficiently through the ear canal, eardrum, and/or ossicles of the middle ear. It is commonly caused by wax in the ear canal, fluid in the middle ear, or a perforation of the eardrum, bony fixation of tiny hearing bone (stapes). Other causes include absence/malformation of the outer ear, ear canal or middle ear. Conductive losses are often correctable with medical or surgical treatment.
• Sensorineural hearing loss – results from pathology associated with the inner ear (i.e. cochlea or cochlear nerve). In adults the main cause is Senile deafness(Presbycusis). Exposure to loud noise, head trauma, infection, Sudden Sensorineural Hearing loss (SSNHL), Meniere’s disease are the other causes. Common causes of sensorineural loss in children include congenital factors (genetic, prenatal, perinatal, or postnatal infections) or acquired factors (i.e., meningitis, ototoxicity associated with certain drugs). Sensorineural losses are generally permanent and may be unmanageable medically.
• Mixed hearing loss – occurs when there are elements of both sensorineural and conductive hearing loss.