Types of Hearing Loss
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and/or the tiny bones (ossicles) of the middle ear. This type of hearing loss can often be corrected medically or surgically.
Some possible causes of conductive hearing loss:
• Fluid in the middle ear from colds
• Ear infection (otitis externa/ otitis media)
• Poor eustachian tube function
• Perforated eardrum
• Benign tumors
• Impacted earwax (cerumen)
• Presence of a foreign body
• Absence or malformation of the outer ear, ear canal, or middle ear
Sensorineural hearing loss (SNHL) occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss.
SNHL results in decreased audibility, reduced dynamic range, reduced frequency resolution, reduced temporal resolution and increased listening fatigue. This affects individuals with all levels of SNHL, even those with mild levels of hearing loss, thereby reducing speech discrimination and clarity.
Some possible causes of SNHL:
• Illnesses or viral infections
• Drugs that are toxic to hearing (ototoxic)
• Hearing loss that runs in the family (genetic or hereditary)
• Head trauma
• Malformation of the inner ear
• Exposure to loud noise
Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss (SNHL). In other words, there may be damage in the outer or middle ear as well as in the inner ear (cochlea) or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss.