Hyperacusis
Hyperacusis is the medical term used to describe abnormal discomfort caused by sounds that are tolerable to listeners with normal hearing.
It is an elusive phenomenon. Because it is a subjective experience it cannot be measured directly and is, consequently, very difficult to study.
Hyperacusis should be distinguished from another, better understood phenomenon called 'recruitment'. Recruitment is commonly associated with hearing loss caused by damage to the sensory cells of the inner ear and occurs because, although weak sounds cannot be heard, louder sounds are perceived at their normal level, causing discomfort and pain. Many people who experience hyperacusis have no detectable hearing loss, although it can be linked with other hearing problems such as tinnitus and Ménière's Disease.
There are probably a number of different causes for hyperacusis, but recent research indicates that one cause may be a reduction in a brain chemical that controls the amount of information arriving at the brain from the sense organs. For this reason it may occur with visual over-sensitivity, or photophobia, as seen in migraine sufferers.
Hyperacusis may follow a blow to the head or exposure to loud noise but, for many people, the onset is sudden and inexplicable.
It may occur independently of any other identifiable disorder. However, hyperacusis is a recognised symptom of several conditions. Aside from tinnitus and Ménière's Disease, hyperacusis is sometimes also associated with post-traumatic stress disorder, migraine, some types of depression, vitamin B6 deficiency, Tay-sach's Disease and post viral fatigue syndrome (or ME).
It is particularly prevalent in people suffering from a genetic disorder known as Williams Syndrome. Other symptoms of this condition are failure to thrive in early life, developmental delay, cardiac problems, small stature and distinctive facial characteristics.
Not all sounds cause adverse reactions in hyperacusis sufferers. It may be a feature of the sound rather than its volume that causes distress. Electrical and machine noise seem to be among the sounds least well tolerated. Hyperacusis may describe the sensation caused by particular sounds as 'painful', 'startling' or 'anxiety producing' but it is still not clear why individual sufferers are disturbed by some sounds while other, often louder sounds, do not cause problems.
Adult sufferers may avoid noisy situations and become socially isolated; for some their condition worsens at night causing extreme sleep disturbance. For children, common sounds such as those from a washing machine or a lawn mower can cause extreme distress. At school, background noise can make concentration very difficult with subsequent poor achievement.
Although children may find that the problem lessens with time, this does not seem to be the case in adults. In fact where sounds have become associated with pain or discomfort, fear or anxiety about these sounds may become established, turning acute hyperacusis into a chronic, debilitating condition.
How common is hyperacusis?
As many as 90% of people with Williams' Syndrome may experience hyperacusis. Aversion to particular sounds can be observed in 40% of those people with communication disorders or autistic features.
A Deafness Research UK study suggests that in childhood, 6% of the general population may suffer oversensitivity to noise. The prevalence in the general adult population is around 7-8%.
How are the symptoms of hyperacusis managed?
There are a number of treatment strategies for hyperacusis, but most will involve learning to understand the kind of noise that can trigger pain/anxiety alongside a process of auditory desensitisation.
