In one clinic, several serious cases were evaluated where simple soft auditory stimulations of less than 30 decibels (comparable to a mid-pitch musical note played at a very soft level) elicited loss of consciousness and seizures. Head trauma in a motor vehicle accident can set off an autoimmune reaction in the inner ear that can destroy the nerve cells, often weeks or months after the initial injury. In addition, autoimmune disease, which can be triggered by many different causes, can harm the balance organ. These cells may suffer damage from trauma such as head injury, metabolic disruptions due to chemical ingestions (e.g., medications or anesthesia), or circulatory changes due to heart disease or artery blockages. In vestibular hyperacusis, we suspect that the main pathology results from damage to the nerve cells in the balance system. Changes in the transmission of electrical signals along complex neural pathways are also highly possible in cases of head injury. Other possible explanations of cochlear hyperacusis involve brain-chemistry dysfunction or head trauma that damages the chain of tiny bones in the middle ear that amplify sound and help transmit vibrations to the inner ear fluid. For example, the sound of a passing car is interpreted as comparable to the roar of a jet engine! In hyperacusis, the mechanism that regulates amplification erroneously magnifies the incoming sounds and noises instead of reducing them. The physiologic conditions underlying these symptoms cannot be identified with certainty because of difficulties involved with studying the very small inner ear structures without damaging them.Ī suspected cause of cochlear hyperacusis involves a loss of the regulatory function provided by the system that conducts impulses along the auditory neural pathways. In addition, many subjects with hyperacusis feel distinct cognitive changes during these exposures and will describe themselves as being “out of myself” or disassociated from reality, unable to take in other stimuli, having an immediate feeling of something being wrong or a sensation of being unwell or experiencing severe confusion. In both cochlear and vestibular hyperacusis, headache is common. In some cases, vestibular hyperacusis can affect the autonomic system and cause problems such as loss of consciousness, mental confusion, nausea, or extreme fatigue. Some of the same reactions as with cochlear hyperacusis can also occur, along with sudden severe vertigo or nausea. Such disturbances have been called by various names, including Tullio’s syndrome and audiogenic seizure disorder. In vestibular hyperacusis, exposure to sound can result in falling or a loss of balance or postural control. Severe emotional reactions may also occur crying or panic reactions are not uncommon. Most people react by covering their ears or leaving the room. With cochlear hyperacusis, subjects feel ear pain, discomfort, annoyance, and irritation when certain sounds are heard, including those that are very soft or high-pitched. The signals coming in are identical to those that present to a normal ear, but the reaction in the abnormal system is markedly different: for example, the sounds in a quiet library may seem like a loud parade to a person with hyperacusis. Hyperacusis is an abnormal condition in which the complex electrical signals generated by sound vibrations are misinterpreted, confused, or exaggerated. The balance system uses lower-frequency sensations to help maintain posture in relation to gravity. Sounds are detected as energy vibrations the human cochlea can hear best the frequencies associated with speech. Both systems are filled with fluid whose movement stimulates tiny sensory cells. The hearing and balance systems of the inner ear are interconnected. It has not been sufficiently studied in the adult population and is often ascribed to psychological conditions rather than being recognized as a physiologic symptom of cochlear or vestibular damage. Hyperacusis can be associated with auto-immune disorders, traumatic brain injury, metabolic disorders, and other conditions. In serious cases, it can cause seizure-like activity in the brain. The effects of hyperacusis can range from a mild sense of unease to a complete loss of balance or upright posture with severe ear pain. The particular symptoms of cochlear hyperacusis and vestibular hyperacusis can help physicians and audiologists distinguish between the two disorders. Hyperacusis is the perception of unusual auditory sensitivity to some environmental noises or tones.
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