Terri Schiavo suffered severe, irreversible brain damage that left that organ discolored and scarred, shriveled to half its normal size, and damaged in nearly all its regions, including the one responsible for vision, according to an autopsy report released yesterday.

Although the meticulous postmortem examination could not determine the mental state of the Florida woman, who died March 31 after a judicial and legislative battle over her "right to die," it did establish the permanence of her physical condition.

Schiavo's brain damage "was irreversible . . . no amount of treatment or rehabilitation would have reversed" it, said Jon R. Thogmartin, the pathologist in Florida's sixth judicial district who performed the autopsy and announced his findings at a news conference in Largo, Fla.

Still unknown is what caused Schiavo, 41, to lose consciousness on a winter morning in 1990. Her heart beat ineffectively for nearly an hour, depriving her brain of blood flow and oxygen.

A study of her organs, fluids, bones and cells, as well as voluminous medical records, failed to support strangulation, beatings, a drug overdose, complications of an eating disorder or a rare molecular heart defect. All had been offered as theories over the past 15 years. Thogmartin said the cause will probably never be known.

Schiavo died at a hospice in Pinellas Park, Fla., on March 31, 13 days after a feeding tube was removed from her stomach at the request of her husband, Michael. He said she would not have wanted to live in such a diminished state.

Schiavo left no living will, and her husband's request was granted only after a long court battle culminating in a judge's order to remove her feeding tube. Her parents, Robert and Mary Schindler, of St. Petersburg, Fla., opposed Michael Schiavo. They believed their daughter interacted with them, including looking at objects they held. They said they were willing to care for her indefinitely.

Over the years the Schindlers' supporters included state lawmakers and members of Congress, Florida Gov. Jeb Bush (R), President Bush, Pope John Paul II and thousands of protesting citizens.

Yesterday's autopsy findings bring to an end one of the odder chapters in recent congressional history. It culminated with lawmakers interrupting their Easter recess to order federal courts to consider whether Schiavo's civil rights had been violated by the removal of her feeding tube. It was an unprecedented intervention into the life of a single citizen, but one that Republicans leading the effort said was necessary because Schiavo's life was at stake. The Supreme Court twice refused to intervene in the days preceding her death.

Those same GOP lawmakers said yesterday that the autopsy results do nothing to undermine their legal case.

"My concern was for due process, and due process is not a medical issue," said Sen. Mel Martinez (R-Fla.). Asked whether he had any regrets, Sen. Rick Santorum (R-Pa.), who visited Schiavo at the hospice in her last days, responded, "None whatsoever." He added: "If a state court decides to take the life of someone, there should be a federal review."

As the debate in Congress peaked, numerous lawmakers made long-distance assessments of Schiavo's mental capacities.

House Majority Leader Tom DeLay (R-Tex.) said Schiavo "talks and she laughs and she expresses happiness and discomfort." He said she was unable to speak because "she's not been afforded any speech therapy -- none!"

Senate Majority Leader Bill Frist (R-Tenn.), a physician, questioned the diagnosis of a persistent vegetative state for Schiavo, based on video footage of the patient, for which he was criticized by some medical authorities. Frist told reporters he had not had time to review the autopsy report.

"We're very pleased the medical examiner confirmed what we have been saying about Mrs. Schiavo's condition for over a decade," said George J. Felos, the lawyer for Michael Schiavo.

Barbara Weller, a lawyer for her parents, said they are "still not convinced that Terri was in a persistent vegetative state." She said they wish she had gotten more testing to determine her level of consciousness with more certainty.

Thogmartin confirmed that Schiavo's immediate cause of death was "marked dehydration -- she did not starve to death." As measured by the balance of salt and water in body fluids, the dehydration was the most severe he had ever seen, he said.

Examination of the heart showed no evidence of damage from a heart attack. A study of her genes by the New Haven, Conn., company Genaissance found no evidence of mutations causing Long QT syndrome, an increasingly recognized cause of sudden cardiac death in otherwise healthy young people.

A review of Schiavo's records confirmed that she was "not a candidate for oral hydration or nutrition," and could not take enough by mouth to sustain life, Thogmartin said. A toxicology study found only "therapeutic levels" of acetaminophen (the pain reliever also sold as Tylenol) and no evidence Schiavo was given substances that hastened her death.

The condition of her brain was "consistent with a persistent vegetative state," said Stephen J. Nelson, a neuropathologist in Winter Haven, Fla., who was consulted by the medical examiner's office.

Some people argued that Schiavo was in a "minimally conscious state," a recently formulated condition defined as a notch above "persistent vegetative state." Both states, however, are diagnosed by examining a living patient. Neither can be confirmed with certainty on the basis of autopsy findings.

Although destruction of the "visual cortex" of the brain had left Schiavo blind, it is remotely possible she could have responded to some visual stimuli through a strange phenomenon known as "blindsight." In that condition, people who have no conscious vision sometimes can direct their eyes toward bright or moving objects because the nerve pathways leading from the eye are intact, even though the destination of those pathways is destroyed.

On the subject of what might have caused Schiavo's original collapse, Thogmartin was skeptical that it was from an electrolyte imbalance brought on by an eating disorder.

Although Schiavo had lost about 100 pounds by dieting in the years before she went into a vegetative state, she never confessed to an eating disorder and nobody saw behavior suggestive of one. The principal evidence for that theory was a very low level of bloodstream potassium when she was admitted to the hospital in 1990.

Vomiting and laxative abuse can cause low potassium. The normal serum level is 3.5 to 5 millimoles per liter. Schiavo's was 2, a level that can cause the heart to beat weakly or stop. However, intravenous fluids and the heart-stimulating drug epinephrine -- both given in large quantities in an effort to resuscitate her -- can lower potassium. He suspects that is the explanation.

"Once you eliminate the potassium problem, you end up with a 26-year-old who used to be heavy, who had lost a lot of weight and is reveling in her new looks," Thogmartin said. "If that's a bulimic, there are a lot of bulimics out there. It's just not enough."

The autopsy was performed the day after Schiavo died. It included 72 photographs of the outside of her body; 116 photographs of internal organs; 58 X-ray views before the autopsy and 28 during and after it -- 274 images in all.

Medical examiner Jon Thogmartin, right, said Terri Schiavo suffered "irreversible" brain damage.