Date: Fri 04-Sep-1998

Publication: Bee

Author: CURT

Quick Words:

Yale-Everest-headaches-health

Full Text:

Yale's Mount Everest Project May Yield Answers About Headaches

By Brigitte Greenberg

Associated Press

NEW HAVEN -- Yale University scientists who monitored Mount Everest climbers

say they have new clues to what causes a rather ordinary affliction -- the

high-altitude headache.

The evidence indicates that people do not get headaches at high altitudes

because of less oxygen in the brain, as the researchers previously believed,

but rather because of overwhelming blood flow to the brain.

"We know categorically that in high-altitude headaches, the mechanism is

different than what we thought all along," said Dr Richard Satava, professor

of surgery.

Many people suffer headaches on the upper floors of tall buildings, while

driving through mountains or riding in airplanes.

The research could help lead to treatments for the common headache and the

more severe migraine headache, and also help doctors better understand normal

fetal development, some experts say.

The treatment commonly available for high-altitude headaches is a diuretic and

respiratory stimulant called Diamox. But it is not effective in all cases.

Many mountain climbers can adjust to the altitude gradually as they climb.

Some wear masks attached to oxygen canisters, but those do not always provide

enough oxygen. Others simply can not adapt.

On Everest, a lack of oxygen, or hypoxia as it is known, is often accompanied

by intense headaches that can impair decision-making, cause sluggishness and

disorientation, and hinder coordination. Some people can die suddenly from

cerebral edema -- swelling of the brain.

"I've known a lot of people who have these bad headaches," said Ed Viesturs,

star of the IMAX movie "Everest", who has reached the peak of Everest, 29,028

feet above sea level, five times. "There are many who, their vision starts to

blur, speech gets slurred. ... They lose their balance. They're not rational."

In those situations, climbers have to be carried down to where a helicopter

can land and take them away, Viesturs said.

"They don't have a sense of what the lack of oxygen can really do to you

almost until it's too late," he said. "Maybe if they discover what the actual

mechanism of the headache is, we could save some people's lives."

The researchers, who hope to publish their research in a peer-reviewed journal

this fall, believe high-altitude headaches may be the body's way of warning

climbers to descend before the brain suffers terrible consequences.

Adapting In

Different Ways

In the study conducted last spring, doctors at Everest Base Camp, 17,500 feet

above sea level, examined 38 climbers from various international expeditions,

as well as native Sherpas who accompany the climbers.

Using a portable ultrasound device, the researchers measured the rate of blood

flow in the carotid artery to the head and compared that with the rate in the

brachial artery that feeds blood to the forearm.

The data showed a fourfold increase in the flow of blood to the head,

according to Dr Ronald C. Merrell, chairman of Yale's Department of Surgery.

The climbers adapted to the low oxygen flow in a variety of ways.

Some breathed harder, gasping for air at the higher altitudes. The bodies of

others automatically increased the number of blood cells in the bloodstream.

And others -- those who had headaches -- experienced a marked increase in

blood flow to the brain. Some climbers experienced a combination of the three

conditions.

Principal researcher Dr Christian Macedonia said the increased blood flow to

the brain was a way to compensate for the low levels of oxygen on Everest.

"We each have our own little scheme for adapting to the environment," said

Macedonia, an Army major who practices at the Walter Reed Army Medical Center

in Washington.

Some who get headaches suffer mini-strokes in the brain. Other climbers

experience lapses in short-term memory while on the mountain or long periods

of forgetfulness after being on the mountain.

Similar research has been conducted on animals. Earlier this year, faculty at

the University of Buffalo studied sheep that were placed in a pressurized

chamber. Cerebral blood pressure forced apart cells and allowed fluids to

accumulate in and around brain tissues, causing swelling of the brain.

UB neurologist Dr Daniel Rifkin said the findings of the Yale study, the first

in such an inhospitable environment, did not surprise him.

"It's almost like brain congestion," Rifkin said. "We don't really know the

ramifications of long-term exposure to low oxygen levels. We need to find ways

to protect those tissues."

Shedding Light

On Other Headaches

Dr Keith Campbell, editor of the journal Headache and former president of the

American Association for the Study of Headache, said the Yale findings make

sense. But because this was the first time carotid blood flow was measured in

people in such conditions, he said he would like to see further research.

"The lack of oxygen would have to change some mechanism in the brain," he

said. "It throbs. You know there's more blood going through your head because

of the pounding sensation."

Campbell said the findings may shed light on methods to treat some form of

migraine headaches.

Macedonia, who specializes in obstetrics and gynecology and teaches at

Georgetown University, said the research also may answer questions about fetal

development in the womb. He noted that babies who have a weak placental

connection to the mother often are born with well-developed heads but withered

bodies.

"The fetus has to do all sorts of things to extract oxygen from the mother

through the placenta. When the placenta becomes sick, the fetus still has to

get oxygen to the brain, and the brain will overcompensate at the expense of

the rest of the body," he said. "The environment in utero is a lot like being

on Mount Everest."

Once the child is born and has full access to oxygen, the body often develops

normally over time, he said, but the long-term effects are unknown.