What is inner ear hearing loss?
What is hearing loss? There are almost nine million people in the UK alone with some degree of deafness and in over 80% of cases this has resulted from damage to the inner ear (the cochlea).
Sensorineural deafness results mainly from damage to cells in the inner ear known as “hair” cells. These highly complex sensory cells, so called because of tiny bundles of hair-like strands at their tips, detect the sound vibrations which are passed from the outside world, via the eardrum and the bones of the middle ear, to the cochlea. Here they are converted into electrical signals that can be processed and understood by the brain.
What causes inner ear damage?
Exposure to a lifetime’s worth of everyday noise is the most common cause of inner ear damage and over half of all people over 60 are affected. With age, the eardrum loses its elasticity and the joints of the tiny middle ear bones begin to stiffen, restricting the transmission of sound waves from the outer ear to the cochlea. At the same time, the sensory hair cells begin to malfunction or die.
Exposure to excessive noise also damages and kills hair cells, resulting in permanent hearing impairment. With many young people risking their hearing through regular exposure to hazardously loud noise, the number of people affected by permanent noise damage to hair cells appears to be increasing.
Over the past 10 years, scientists have made a lot of progress in understanding the exact process by which noise-induced hearing loss occurs. Very loud noises are thought to over-stimulate the sensory hair cells leading to the over-production of potentially damaging chemicals called free radicals. While cells can normally cope with a low level of free radicals, too high a level will damage the structure of the cell and eventually lead to its death.
Hair cell damage can also be caused by ‘ototoxic’ agents, chemicals (including some therapeutically useful drugs) which are toxic to both the auditory (hearing) and vestibular (balance) portions of the ear.
Is there a treatment for inner ear damage?
At present, there is no medical way in which cochlear damage can be prevented or reversed. Consequently, for most people with a hearing loss, hearing aids and other technological aids are the only option.
How likely is a medical treatment for inner ear damage?
Only a few years ago, most scientists would have considered it unlikely that hair cell damage could ever be prevented or reversed by medical means. Today, many believe that it won’t be too long before we find medical ways of preventing or slowing down some forms of hearing loss. One day, it might even be possible to reverse or “cure” deafness medically. Deafness Research UK is supporting research in this area at specialist centres around the UK.