Research published today by a University of Michigan team is sorting out the answers.

Sudden deafness occurs abruptly or gradually over a few weeks. It is diagnosed in an estimated 4,000 Americans each year, according to the Deafness Research Foundation.

The reasons for the problem aren't well known. Sometimes it is associated with autoimmune diseases such as lupus and rheumatoid arthritis. Other possible causes are infectious diseases, prescription medicines, head injury and circulatory problems.

Larry Burns, vice president for research and development and planning at General Motors Corp., is one of the more prominent Americans with the problem who has shared his story publicly (http://www.freep.com/news/health/hear4_20011204.htm) first bout of hearing loss was in 1991. Steroid treatment restored it.

After a second episode in 1993, steroids didn't work. "If the steroids help you, it's pretty important to get in there pretty quick," Burns says.

Sorting out who benefits from steroids is important because the drugs can cause ulcers, water retention, muscle deterioration and liver damage, says Thomas Carey, PhD, associate chair of research in U-M's otolaryngology department. He is senior author of a study in the August issue of Archives of Otolaryngology -- Head and Neck Surgery.

The research clarifies an immune system process associated with rapid-onset hearing loss. It involves a protein found in an inner-ear structure called the organ of Corti. The organ houses hair cells that move in response to vibration, generating nerve signals to the brain involved with hearing.

The protein is needed for normal function in the ear, Carey says. People with sudden hearing loss develop antibodies, or foreign substances, to the protein that are associated with hearing loss.

U-M is working with Immco Diagnostics (www.immcodiagnostics.com ), a Buffalo, N.Y., firm, to develop a test more accurate than one administered in emergency departments to determine which patients might best respond to steroids.

The test is not available anywhere, not even at U-M, and is several years away from commercial use.

By Patricia Anstett