Aug. 6, 1998 In a medical breakthrough that will help tens of millions of Americans at risk for noise-induced hearing loss, the Naval Medical Center in San Diego has successfully tested a technique that restores hearing loss if administered within hours following exposure to loud noise. It can also "inoculate" users against hearing loss if taken before such exposure.
The technique uses micro-devices or micro-catheters inserted in the ear to deliver antioxidant pharmaceuticals that protect the hypersensitive hair cells within the ear that are fundamental to sound detection. These pharmaceuticals have already been approved by the FDA for other applications; it is anticipated that the antioxidants will be on the fast track for approval for the clinical trials using human subject of this research.
Although the ear can tolerate an amazing range of sound intensities, a day of 85 dB noise, the equivalent of standing behind a gas lawn mower, can begin to damage the cochlea. Damage rapidly escalates with sound level exposures to 120 dB sound pressure level, the equivalent of standing in front of the speakers at a rock concert. At around 130 dB sound pressure level, mechanical destruction of the inner ear begins. Excessive noise initially damages the inner ear by generating toxic oxygen-containing compounds that damage nerve endings and hair cells by chemical means. Although damage begins soon after noise exposure, actual hair cell loss does not begin for four to five days and progresses over the next 40 days. This presents a window of opportunity in which damaged hair cells may be rescued through the administration of antioxidant pharmaceuticals.
"The techniques have already been used to treat hearing loss and Meniere's diseases, and have significant implications for treating other hearing and balance disorders in the military and civilian population," says co-principal investigator, Dr. Richard D. Kopke, Colonel, Army Medical Corps. Sponsored by the Office of Naval Research and the U.S. Navy Bureau of Medicine and Surgery, this research addresses issues of critical concern to the United States military.
- The military spends more than $1.5 billion in compensation, re-training,
and equipment replacement each year due to hearing and balance disorders,
- More than 11 percent of individuals in the military are affected by
- Deafness affects 30 million Americans and costs the nation $56 billion
- An additional 40 million individuals work in environments that pose a
significant threat to their hearing,
- 50 percent of individuals suffer a balance disorder at some point during
To further address hearing and balance problems that affect military and civilian personnel, the Defense Spatial Orientation Center (DSOC) was established. Dr. Michael Hoffer, Lieutenant Commander, Navy Medical Corps, co-principal investigator with Dr. Kopke, explains that the group is "unique in that it brings together investigators from a number of different centers" to bring medical treatment directly to where military personnel work.
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