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Tinnitus is a phenomenon of the nervous system connected to the ear, characterised by perception of a ringing or beating sound (often perceived as sinusoidal) with no external source. This sound may be a quiet background noise, or loud enough to drown out all outside sounds. Causes of tinnitus include:
- A sudden loud noise,
- Hearing loss (20 per cent of cases: chronic noise damage and presbycusis),
- Head injury (especially basal skull fracture),
- Drugs: aspirin overdose, loop diuretics, aminoglycosides, quinine,
- Temporomandibular and cervical spine disorders,
- Suppurative otitis media (also chronic infection and serous OM),
- Otosclerosis,
- Ear wax,
- Meniere's disease,
- Impacted wisdom teeth,
- Hypertension and atherosclerosis,
- Acoustic neuroma,
- Palatal myoclonus (objectively detectable),
- Arteriovenous fistulae and arterial bruits (objectively detectable),
- Severe anemia and renal failure,
- Glomus jugulare tumours (objectively detectable),
- Lyme Disease
- Stress and depression
- Thyroid disorders, such as hyper- or hypothyroidism
Tinnitus can be objective (the sound, e.g., a bruit, can be perceived by a clinician) or subjective (perceived only by the patient).
Some types of tinnitus can be treated while others are permanent. In general, there are no cures specific to tinnitus, but if it is caused by a physical condition that can be treated, the tinnitus may also resolve. Chronic tinnitus can be quite stressful psychologically as it distracts the affected individual from mental tasks and interferes with sleep, particularly when there is no external sound. The affected individual may have to generate artificial noise that masks the tinnitus sound. A combination of external masking and psychological counseling known as Tinnitus Retraining Therapy is widely practiced. While it does not actually cure the tinnitus, many report that it becomes much less disturbing and easier to ignore.
The mechanisms of subjective tinnitus are often obscure. While it's not surprising that direct trauma to the inner ear can cause tinnitus, other apparent causes (e.g., TMJ and dental disorders) are difficult to explain. Recent research has proposed that there are two distinct categories of subjective tinnitus, otic tinnitus caused by disorders of the inner ear or the acoustic nerve, and somatic tinnitus caused by disorders outside the ear and nerve, but still within the head or neck. It is further hypothesised that somatic tinnitus may be due to "central crosstalk" within the brain, as certain head and neck nerves enter the brain near regions known to be involved in hearing.
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