Causes of Tinnitus
Causes of Tinnitus
There are many causes of tinnitus, and often the cause is unknown. Just about anything that can cause hearing loss can also cause tinnitus. The most common causes are: Noise exposure (e.g. from shooting or machines at work), a natural part of the aging process, head injury (e.g. from a car accident or fall), as a side effect of medications (e.g. aspirin).
Tinnitus is almost always accompanied by hearing loss. If you have tinnitus, you should have your hearing tested by a hearing health professional. Some 30 million adults suffer from persistent tinnitus (it can also affect children). For 12 million, the problem is severe enough that it impacts their everyday life. Because tinnitus can be a symptom of a more serious disorder, it is important to have an appropriate health evaluation.
Nearly four in ten people experience tinnitus 80% of the time during a typical day; slightly more than one in four people describe their tinnitus as loud; and about one in five describe their tinnitus as disabling or nearly disabling. Tinnitus is sometimes accompanied by hyperacusis (when moderately loud sounds are perceived as very loud).
A Summary of the Causes of Tinnitus
Tinnitus may originate from various lesions and from different sites. The auditory system involves highly complicated inner ear structures, many afferent and efferent nerve pathways and a great amount of nuclei that form a complex meshwork. To pinpoint tinnitus to a certain structure becomes questionable. This is demonstrated by patients who have had intractable tinnitus after having surgery on their ear or incurring severe diseases of the ear. In an attempt to relieve the tinnitus, cutting the auditory nerve has been done and yet the tinnitus was persistent, indicating the site of lesion causing the tinnitus must have shifted into the central nervous system.
Tinnitus could be explained by abnormal neural activity in the auditory nerve fibers, which may occur if there is a partial breakdown of the myelin covering of individual fibers. A defect in the hair cell would trigger the discharge of connected nerve fibers. For chronic cochlear disorders, there may also be increased spontaneous activity in the hair cells and neurons resulting in tinnitus. In the auditory nerve there are two different kinds of afferent fibers: Inner hair cell fibers with large diameters and outer hair cells fibers with small diameters. Thus, loss of signals from the cochlea might trigger tinnitus as a manifestation of a functional imbalance between the two sets of fibers. In addition, other abnormal changes of the cochlear fluids may result in tinnitus.
There is not one type, one site or one origin of tinnitus, but a multitude of types, sites, and origins. It is also unlikely that one hypothesis on the cause of tinnitus could explain all the features.