For most people, loss of hearing will develop slowly over many years. Only becoming apparent gradually, friends and family are often the first ones to notice. This can mean that those affected may often not realise they are actually suffering from a hearing impairment. Many people also don’t recognise the severity of their hearing condition.
There are three main types of hearing loss. These are known as sensorineural, conductive and mixed.
Sensorineural hearing loss
This is the most common condition and also the most associated with age related deterioration. As the word sensorineural would suggest it combines two areas. Sensory hearing loss, eg, the issue lies within the inner ear, and neural hearing loss where the issue is related to failings with the auditory neural pathway. Essentially the inner ear is unable to transmit sound properly to the brain. The hair cells inside the inner ear (especially those that are responsible for high frequency hearing) have deteriorated due to age, noise, disease, medications or a combination. This means they are no longer able to pick up the nerve impulses properly.
This type of condition is permanent, the hair cells do not re-grow and typically it will affect both ears. The effects of sensorineural loss are a reduced sensitivity to sounds as well as a reduced ability to discriminate between sounds.
Possible causes
- Age-related hearing loss (presbyacusis) – Many people get this as they get older, it is a natural decline in hearing due to damage of hair cells within the inner ear (cochlea).
- Damage to the hair cells by loud noises (acoustic trauma) – This is most likely to be seen in those that have worked in noisy places, such as industry.
- Genetics – Hearing loss can be from birth. Around 1 in 1000 babies are born with a moderate to severe condition. It is thought that at least half of these are caused by genetic factors.
- Medication – Some prescribed, quite routine drugs can cause ‘ototoxicity’ which can result in permanent loss of hearing. Common examples are quinine, aspirin or warfarin with many more if taken in high doses over an extended period of time.
- Infections including measles, mumps or meningitis.
- Ménière’s disease – causes hearing loss, vertigo and tinnitus (ringing in the ears).
- Certain cancer treatments – treatments such as chemotherapy and radiation therapy are known to cause loss of hearing.
- Acoustic neuroma – This is a benign (non-cancerous) tumour which creates pressure on the auditory nerve and can cause deafness and tinnitus.
- Cholesteatoma – this is a benign skin growth in the middle ear, causing deafness and vertigo, it can be very serious if left untreated.
Conductive hearing loss
This is where sound isn’t transmitted properly from the outer or middle ear to the inner ear. It can be caused by physical obstructions, for example excess wax build up. It could also be due to other abnormalities, such as a perforated eardrum or defective ossicles in the middle ear. This can mean that sound isn’t received fully by the inner ear and therefore can not pass through the auditory system to the brain. Conductive hearing losses are not always permanent and can sometimes be rectified by medical intervention.
Possible causes
- Blockage of the outer ear – eg excessive ear wax build up
- Collection of fluid in the middle ear – often known as ‘glue ear’
- Middle ear infections – known as acute otitis media
- Otosclerosis – This is a condition where the bones in the middle ear (ossicles) become hardened with calcium deposits and have reduced mobility.
- Damage to the ossicles – possible due to a head trauma or serious infection
- Perforated eardrum – possible due to a head trauma, untreated infection or from poking objects in to the ear.
Mixed hearing loss
This is where a person has a combination of both sensorineural loss and conductive loss.
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