The following was in the NY Times.
Enjoy.
Jeff Nagelbush
[EMAIL PROTECTED]
Ferris State University
If Things Taste Bad, 'Phantoms' May Be at Work
By ERICA GOODE
Until he bit into a piece of raw cabbage on that
February evening in
1997, Dr. Raymond Fowler had not thought much about the
sense of
taste.
The cabbage, part of a pasta dish he was preparing for his
family's dinner,
had an odd, burning taste, but he did not pay it much
attention. Then a few
minutes later, his daughter handed him a glass of cola, and
he took a
swallow. "It was like sulphuric acid," he said. "It was like
the hottest thing
you could imagine boring into your mouth."
Over the next few weeks, Dr.
Fowler, who is the chief
executive officer of the
American Psychological
Association in Washington,
realized that something was
badly askew in his gustatory
world. Everything he ate tasted
like "unsalted dough." Ice water
was painfully sweet, "as if
someone had added three
packages of Equal." An
unpleasant salty sensation
gathered at the back of his
mouth and would not go away.
When eating finally became so
unpleasant that he was reduced
to swigging down high-nutrition supplements, Dr. Fowler
sought help from a
colleague, Dr. Linda Bartoshuk, a Yale University
psychologist specializing in
the study of taste.
In Dr. Bartoshuk's lab, Dr. Fowler's cranial nerves were
tested for taste and
for pain, his tongue was painted with blue food coloring and
videotaped in
action, his ability to smell turpentine, coffee and other
odors was tested, and
a thorough examination was conducted of his mouth, including
the fungiform
pappilae, the structures that house taste buds, on his
tongue. Then Dr.
Bartoshuk delivered her diagnosis: the burning sensations
and mysterious
tastes, she told him, were sensory phantoms, his brain's
response to damage
to the chorda tympani, a branch of the VII cranial nerve
that serves taste
buds in the front of the tongue, runs through the middle
ear, and carries taste
messages to the brain.
The damage, Dr. Bartoshuk said, was probably temporary, and
might be the
result of a medicine Dr. Fowler was taking, or by a viral
infection. And a few
months later his sense of taste did return to normal.
The most familiar example of phantom sensation is phantom
limb syndrome,
in which a patient continues to feel pain in an arm or leg
long after the limb
has been amputated. But phantoms can occur in any of the
senses. Tinnitus,
or constant ringing in the ears, is a type of auditory
phantom. People who
have lost much of their vision often experience visual
phantoms.
Doctors historically have viewed phantoms of taste and smell
as insignificant
-- if annoying -- side effects of injury or illness, or
dismissed them as
neurotic symptoms. When the composer George Gershwin
reported
experiencing, among other complaints, a persistent smell of
burning rubber,
for example, he was told by doctors that he had a nervous
affliction.
Gershwin died a few years later of a brain tumor.
In recent years, however, a surge of scientific interest in
the mechanisms of
human taste and olfaction has focused new attention on the
ways in which
these senses can become disordered, and as a result,
phantoms of taste and
smell are receiving greater scrutiny. Though there are no
precise numbers,
scientists estimate that such phantom sensations afflict 1
percent or more of
the population.
Dr. Bartoshuk, who has evaluated more than 100 cases of
taste phantoms,
and her colleagues will present some of their work at the
annual meeting of
the Association for Chemoreception Sciences in Sarasota,
Fla., this week.
Because taste and smell are so closely linked, it is
sometimes difficult to tell
which system is in trouble. Patients who suffer from
anosmia, or a loss of
smell, for example, often report to clinics complaining
instead that they have
lost their sense of taste. But taste and smell phantoms, Dr.
Bartoshuk said,
usually can be distinguished by their quality. Bitter,
salty, sweet, or sour
phantoms -- corresponding to four basic categories the
tongue can
distinguish -- are always related to disorders of taste.
Smell phantoms, in
contrast, are usually more complex in nature: patients may
complain of
tasting or smelling rotting food, for example, fecal matter,
gasoline or smoke.
Like Dr. Fowler, some patients who have taste phantoms also
suffer from
"burning mouth syndrome," an intense burning sensation on
the tongue, often
at its tip. When Dr. Bartoshuk examined Dr. Fowler, she
discovered that he
was a "supertaster," someone who has an unusually large
density of taste
buds, each surrounded by pain fibers. Supertasters, Dr.
Bartoshuk has found,
are more likely to develop burning mouth syndrome, as are
post-menopausal
women, who often have lost their ability to sense bitter
tastes.
The link between burning mouth syndrome and taste phantoms
led Dr.
Bartoshuk to theorize that both were the result of damage to
the chorda
tympani, one of three cranial nerves involved in taste.
Scientists have found
that the taste system involves a complicated feedback loop,
with each nerve
acting to inhibit the signals of other nerves. The chorda
tympani, in
particular, appears to exert an inhibitory influence on
other taste nerves, as
well as on pain fibers in the tongue.
When the chorda tympani is damaged, its inhibitory function
is disrupted,
prompting increased activity in other nerves. In an elegant
series of
experiments, Dr. Bartoshuk and Dr. John Kveton, an
otological surgeon at
Yale, have found that when the chorda tympani is
anesthetized, research
subjects experience intensified sensation in area served by
other taste nerves.
In about 40 percent of the subjects, anesthetizing the
chorda tympani
produced taste phantoms, the result, Dr. Bartoshuk argues,
of the
disinhibition.
In other work, to be presented at the chemoreception
sciences meeting, the
psychologist and her colleagues showed that when the chorda
tympani is
anesthetized, pain sensitivity increases in regions served
by the trigeminal
nerve on the opposite side of the tongue. Supertasters, who
have a denser
field of pain fibers, had the greatest increase in pain
sensation. In another
study, the researchers found that patients with burning
mouth syndrome
showed severe damage to the chorda tympani, suggesting pain
phantoms
may appear when the chorda tympani's inhibiting influence is
interrupted. "All
of a sudden, the genie is out of the bottle," Dr. Bartoshuk
said.
The taste system's feedback loop, she said, may make
evolutionary sense,
insuring, for example, that if one nerve is damaged the
others increase their
activity to compensate. This is seen most clearly in
patients whose chorda
tympani nerve has been damaged by ear surgery. Such
patients, doctors find,
rarely complain of taste loss.
Clonazepam, an anti-seizure drug, seems effective in
treating burning mouth
syndrome in more than 70 percent of patients, Dr. Bartoshuk
said, perhaps
because it has an inhibitory action on the brain.
While virtually every taste phantom, she said, can be traced
to nerve damage
somewhere in the taste system, smell phantoms are much more
difficult to
account for. Many are clearly related to a head injury or a
viral illness. But
occasionally, olfactory phantoms appear spontaneously, with
no identifiable
cause.
Dr. Donald Leopold, an associate professor in the department
of
otolaryngology-head and neck surgery at Johns Hopkins
University, says he
has performed surgeries on nine patients who sought his help
after being
plagued by spontaneous smell phantoms that persisted for
years.
His patients, said Dr. Leopold, who will present the cases
at the
chemoreception sciences meeting this week, are usually women
between the
ages of 20 and 40. They come from all walks of life and do
not appear to
have other significant health problems. Typically, he said,
a patient "is going
along with her usual life and at 10 o'clock in the morning
on a Thursday, all
of a sudden she experiences a bad smell."
Often, he said, the odor departs after a short time and
returns intermittently
over a period of months, but eventually becomes a constant
presence.
"They're miserable," Dr. Leopold said. "At some point most
have told me that
it's really not worth living with this."
One woman, he said, claimed the smell went away when her
nose was
irritated. "She bent a paper clip and stuck it up her nose,"
he said.
Kain Blandford, one of Dr. Leopold's patients, was 18 years
old and working
as a waitress when she was struck by what she calls "The
Taste." She
ordered a hamburger and fries at McDonald's, took a bite of
her lunch, and
found that it tasted "really bad," as if something was
rotten. A month later,
the rotten taste returned. When it started happening every
few weeks, she
said, "I realized that this is me, that this is not the
food."
Ms. Blandford began to keep track of the things that brought
the rotten
sensation on: steam, grease, humidity, heavy perfume.
For a while she thought crying caused it to go away, and she
would think
about the saddest things she could imagine in order to make
herself cry. Then
she thought it got better when she pinched her nostrils. "I
started holding my
nose all the time," she said. "I didn't want to tell people
about it because it's
so embarrassing and so strange."
When, three years ago, Ms. Blandford, who is now 29 and a
radio announcer
in Charleston, S.C., reached the point that she had stopped
eating altogether,
she called Dr. Leopold, and underwent surgery shortly
thereafter. By
anesthetizing each side of her nose in turn and testing her
sense of smell, Dr.
Leopold determined that the problem was one-sided. In the
surgery, he
excised the olfactory epithelium high in the nose on the
affected side, cutting
the small nerves that pass up through the bony plate. In
every case, he said,
his patients say that the smell phantom either disappeared
or subsided to a
tolerable level, although some patients underwent more than
one surgery.
Ms. Blandford said her smell phantom returned in much milder
form two
years after the surgery. Given a choice of another operation
or living with the
phantom's remnants, however, she opted for the latter. "It's
a little like having
a low-grade headache all the time," she said.
Still, Ms. Blandford said, she often wonders why she had the
phantom at all:
"When I die and I'm going up that big tunnel, the first
thing I'm going to ask
is, 'Do you mind explaining what that was all about?' "
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