Most causes of tinnitus are not harmful. The main causes are described below.
Inner ear damage
Tinnitus is most commonly caused by damage that occurs inside the inner ear.
Sounds pass from the outer ear through the middle ear and on to the inner ear, which contains the cochlea and the auditory nerve. The cochlea is a coiled, spiral tube that contains a large number of sensitive hair cells. The auditory nerve transmits sounds to the brain.
If part of the cochlea becomes damaged, it will stop sending information to parts of your brain. These areas of your brain will then actively "seek out" signals from the parts of the cochlea that are still working. These signals are over-represented in the brain and cause the sounds of tinnitus.
In older people, tinnitus is often caused by natural hearing loss, which makes the hearing nerves less sensitive. In younger people, tinnitus can sometimes occur as a result of hearing damage caused by excessive noise.
The exact cause of tinnitus cannot always be identified, even after examination by a specialist. However, as well as natural hearing loss and damage, there are several other possible causes of tinnitus. These include:
- a build-up of earwax that blocks the ear
- a middle ear infection (otitis media)
glue ear (otitis media with infusion)
- otosclerosis - an inherited condition where an abnormal bone growth in the middle ear causes hearing loss
Ménière's disease - a condition that affects a part of the inner ear known as the labyrinth and causes balance problems
Paget's disease - a condition where the normal cycle of bone renewal and repair is disrupted
anaemia - a reduced number of red blood cells that can sometimes cause the blood to become thinner and to circulate so rapidly that it produces a sound
- a perforated eardrum
Less commonly, tinnitus may also develop because of:
- a head injury
- exposure to a sudden or very loud noise, such as gunfire or an explosion
acoustic neuroma - a rare, non-cancerous growth that affects the hearing nerve in the inner ear
- adverse reactions to certain medications, such as antibiotics, diuretics, quinine and aspirin (this is more likely to occur when the recommended dosage is exceeded)
- solvent abuse, drug misuse and alcohol misuse
- high blood pressure (hypertension) and narrowing of the arteries (atherosclerosis)
- an overactive thyroid gland (hyperthyroidism)
Stress is not a direct cause of tinnitus but it can sometimes make the symptom worse. For example, some people have reported that their tinnitus became worse during stressful events, such as bereavement.