Hearing Loss From Immune System Attack
Editor: When a person suddenly loses his hearing, doctors often
prescribe steroid therapy in an attempt to restore hearing. This therapy
works in some cases, but not all; unfortunately doctors are unable to
predict in advance which patients will benefit from steroid treatment,
and which will not. They're also unable to explain why it works for some
patients, and not for others.
Researchers at the University of Michigan may be changing that. Here
are portions of a press release describing their recent work. The
complete press release is available at http://www.med.umich.edu/opm/newspage/2005/hearingloss.htm
~~~~~~~~~~~~~~~~~~~
New laboratory research may eventually help those who lose their
hearing due to immune system attacks
University of Michigan-led study may one day lead to test that could
show which patients may be helped by immediate steroid treatment
ANN ARBOR, MI - Our immune system protects us from disease,
destroying invading microbes with a swarm of attacking cells. But it can
also go haywire for no apparent reason, ganging up on normal tissues in
our body and wreaking havoc.
In thousands of people each year, the immune system attacks the inner
ear, home to the tiny, delicate structures that allow us to hear.
Without warning, in days or weeks, patients lose the ability to hear in
one or both ears. Some might get part or all of their hearing back if
they take steroid medicines, but many are left to cope with partial or
total deafness without knowing what caused it. And no one knows why it
happens.
Now, new research based at the University of Michigan's Kresge
Hearing Research Institute may help more patients find out quickly if
steroids could help them, or if they can be spared the drugs' harsh side
effects. It may also expand the definition of the condition, known as
autoimmune sensorineural hearing loss or AISNHL, and help more people
get a firm diagnosis of what's causing their mysterious hearing loss.
Please note, this procedure is not ready for clinical use.
In the August issue of the Archives of Otolaryngology - Head and Neck
Surgery, researchers reports results from a study of 63 people with
rapidly progressing hearing loss in Michigan, Pennsylvania and Indiana,
and 20 people with normal hearing. The patients were suspected of having
an auto-immune cause for their hearing loss, and all received steroids,
but they hadn't been formally diagnosed.
The researchers found that more than half of the hearing-loss
patients had antibodies against a protein found in the inner ear, called
IESCA for inner-ear supporting cell antigen. This is a sign their immune
systems recognized it as foreign.
"In all, 28 of the 63 patients experienced improvement in their
hearing after steroid treatment, and 35 did not. But the vast majority,
89 percent, of those who improved had a positive immunofluorescence test
for an antibody to IESCA that we have studied at U-M for years,"
says senior author Thomas Carey, Ph.D., a professor and distinguished
research scientist at the U-M Medical School and department chair in the
School of Dentistry. "The results strongly suggest that a direct
test for antibodies could accurately predict which patients will regain
hearing with steroid treatment." Such a test, he notes, is still
several years away from being available to patients.
The new findings also may be important to people with systemic
autoimmune disorders such as lupus or rheumatoid arthritis. Such people
may be prone to losing all or part of their hearing due to an
overzealous autoimmune reaction. All eight study participants who had
systemic autoimmune diseases showed signs of antibodies against IESCA.
Six of them regained hearing after steroid treatment.
U-M researchers have been studying IESCA for several years in animals
and have found that it may be a main target of the immune system's
deafening attack on the inner ear. IESCA is found in the supporting
cells that help make up the organ of Corti, a tiny but crucial structure
inside the cochlea, or inner ear.
Inside the organ of Corti are the ultra-sensitive hair cells, whose
movement in response to vibrations creates the nerve signals that are
fed to the brain and interpreted as sounds and speech. Damage to the
organ of Corti and hair cells, whether due to immune system attack, loud
noise, trauma or medications, can diminish or destroy hearing.
[snip]
Interestingly, Carey notes, nearly all of the patients who had sudden
hearing loss over hours or days had antibodies, and nearly all improved
with steroids.
Since this kind of rapid-onset hearing loss has historically been
excluded from the formal definition of AISNHL, Carey suggests the
definition may need re-examining in light of this strong evidence for an
immune-system cause in these patients.
[snip]
Special note for hearing-loss patients: The new findings, while
exciting, are laboratory results and cannot be immediately applied to
human treatment. It will take several years to develop a test that could
be used in patients who have recently developed hearing loss. If you
have recently begun to experience hearing loss that is progressing, seek
immediate attention from an otolaryngologist, sometimes called an ear,
nose and throat (ENT) doctor. He or she can advise you on immediate and
long-term treatment options.
[snip]
Written by Kara Gavin
