Sound Sensitivity: A Summary of Possible Causes
Sound sensitivity has been discussed in previous issues of The Sound Connection and is a topic of continuing interest since this problem is experienced by many individuals who have developmental disorders. It is also seen in some individuals as an isolated problem with no other disabilities being present. This article will summarize current information about causes. The causes of auditory sensitivity can be classified into two categories: biochemical (which includes nutritional deficiency and drug side-effects) and physiological.
It is well established that nutritional effects may result in hypersensitive hearing. Many individuals who are deficient in magnesium suffer from sound sensitivity, and they often experience an improvement after receiving magnesium supplements. According to the Autism Research Review International (1990, Vol. 4, No. 4), 20 milligrams per each 10 pounds of body weight per day, is an appropriate amount of magnesium. Improvement would occur within a few days if the cause of the sensitivity is a magnesium deficiency.
The use of Nutrasweet (aspartame), a popular artificial sweetener, may also lead to hypersensitive hearing. Many chewable children’s vitamins contain aspartame as well as diet and low calorie foods. Labels must be read in detail, as it may not be easily identified that the product contains aspartame.
Some medications have ototoxic side-effects that may result in auditory hypersensitivity and/or other auditory system problems such as tinnitus and vestibular dysfunction. Dr. Guy Berard cautions against the use of antibiotics in the aminoglycocide family, including erythromycin, gentamicin, garamycin, neomycin, tobramycin, etc. Other medications with known ototoxic side effects include: Advil, aspirin (salicyclates), Benadryl, Beta blockers, Desipramine HCI (Norpramin), Empirin, Imipramine (Tofranil), Motrin (ibuprofen), Naltrexone (Trexan), Sel-dane, Tavist, and Tegretol. Author Elaine Suss reports in her book, When the Hearing Becomes Hard, that diuretics are also known for ototoxicity and must be used with caution.
Other biochemical causes include changes in the system due to stress and anxiety. Many people have reported increased auditory hypersensitivity during periods of stress and anxiety, i.e., exam week at college. Other sensory perceptions, such as tactile, taste or smell, may also be heightened. This may be related to stress-induced biochemical changes. Once the stress-related experience is over, the hypersensitivity usually decreases. Nutritional stress formulas may also be helpful.
The sensory system may also be overaroused by changes in the person’s biochemistry, including increases in toxins produced by an overgrowth of yeast and fungus, and possibly exposures to other toxins (e.g., heavy metals, toxic chemicals). Auditory hypersensitivity may escalate during this exposure and may be restored to more normal levels when the toxins are removed. Other techniques, such as brushing therapy, joint compression and deep pressure, can sometimes be used to help calm the nervous system while seeking appropriate treatment for the toxins. Physiological causes may include: damage to the auditory system through exposure to loud noise, traumas such as whiplash, and abnormalities in function of the brainstem or higher cortical areas. A study by Deborah Woodward of Woodward Audiology in McLeansville, NC revealed that in children with autism, the binaural tolerance to speech noise, prior to AIT, was 9 to 11 dBHTL less than the monaural tolerance level (see The Sound Connection, 1994, Vol. 2, No. 2). This may indicate abnormal amplification in the brainstem or lack of bilateral inhibition. A study by Collett et al., published in The Lancet (1993, Vol. 342, pages 923-924), produced results that may indicate an alteration in the functioning of the medial olivocochlear (MOC) bundle which is located in the brainstem, and may explain sound sensitivity in autistic people.
There is also speculation about a possible link between hypersensitive hearing and the amygdala, located in the limbic system of the brain. Dr. Margaret Bauman’s research found that some neurons in the amygdala are abnormal. There are auditory pathways to the amygdala responsible for fear conditioning to sounds. It is possible that the abnormal functioning in the amygdala plays a role in the development of a dysfunctional fear response to sounds. Perhaps AIT stimulates the amygdala in some way that reduces this fear.
It is clear that there are many possible causes of hypersensitive hearing. One must learn about these causes and try to determine what might be the cause for a particular individual. If that can be determined, an appropriate intervention can be selected. When certain things that are possible to control have been ruled out, AIT may be an appropriate intervention to use for decreasing sound sensitivity.
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