A California man who died on Mount Shasta at the end of March succumbed to altitude sickness that caused swelling in his brain.

A California man who died on Mount Shasta at the end of March succumbed to altitude sickness that caused swelling in his brain.

The Siskiyou County Sheriff's Office reported Wednesday that an autopsy on the body of Thomas Bennett, 26, of Oakland, revealed cerebral edema, Detective Sgt. Mark Hilsenberg said.

The autopsy was performed Tuesday, but results were not released to the public until family members had been contacted, Hilsenberg said.

Hilsenberg said a full toxicology report will be performed to determine whether any other substances may have contributed to Bennett's death, and results will be available in about three weeks.

He said a toxicology analysis is a standard procedure for a death investigation, and he did not expect the tests to reveal anything else that might have caused Bennett to fall ill.

"In a case like this, I'd be very, very surprised if (the report) came back with anything questionable," Hilsenberg said.

Physicians do not understand exactly how altitude sickness is caused, but it occurs because there is less oxygen in the atmosphere at high altitudes, which means the blood absorbs less oxygen with each breath. Fluid may collect in the brain or the lungs, with symptoms that may include lack of appetite, nausea, fatigue, weakness, dizziness, drowsiness or insomnia, headache, vomiting, or unsteady gait.

Mark Thomas, of Berkeley, Calif., Bennett's climbing partner, told sheriff's deputies they reached the summit of the 14,000-foot peak on March 27. They planned to descend but dug a snow cave near the summit when the weather deteriorated.

Thomas told deputies that Bennett showed symptoms of mountain sickness on the morning of March 28. Thomas left Bennett in the snow cave and went down the mountain to get help. Stormy weather prevented rescuers from reaching the snow cave until Thursday, April 1, when they recovered Bennett's body.

Vulnerability to altitude sickness varies among individuals. Some may begin to feel the effects at an elevation of 8,000 feet to 9,000 feet, but nearly everyone begins to feel symptoms above 14,000 feet after some hours of exposure.

Climbers try to dodge altitude sickness by gradual acclimatization to height. On major peaks they plan to climb about 1,000 feet higher every day, but Shasta climbers often go from 10,000 feet to the summit in a single day and then descend.

Drugs may be used to treat cerebral edema but patients must be brought quickly to lower altitude to avoid serious illness or death.

Reach reporter Bill Kettler at 541-776-4492, or e-mail bkettler@mailtribune.com.