Nancy Cruzan was allowed to die last week, after a three-year legal battle that went all the way to the Supreme Court and made her an enduring symbol of the right-to-die movement.

Cruzan, who had been kept alive in a deep coma for eight years by artificial feeding, dramatized the dilemma for families and doctors of incapacitated patients: When there is no hope of recovery or meaningful life, what purpose does it serve to keep the patient alive by artificial means?

Karen Ann Quinlan's case raised that question with respect to respirators in the 1970s. Nancy Cruzan's raised it with respect to artificial feeding and hydration.

"This was the first national case, and I think it's going to have a lot of nationwide impact," said Ronald E. Cranford, a neurologist who advised the Cruzan family.

Nancy Cruzan, brain-damaged by a car accident in Missouri in 1983 when she was 25, had been in what doctors call a persistent vegetative state. She could breathe on her own but lacked all cognitive brain function -- the ability to think and feel.

Because she could not swallow, water and liquid nutrients were pumped into her stomach once a day through a tube.

Cruzan's parents asked to have the feeding tube disconnected in 1987, but the state hospital refused to do so without court backing. A county court ruling in the Cruzans' favor was overturned on appeal by the Missouri Supreme Court. In turn, the U.S. Supreme Court issued its first right-to-die decision last June.

By a 5-to-4 vote, the high court said it was constitutional for Missouri to require "clear and convincing evidence" of a patient's wish before allowing withdrawal of life-sustaining treatment. But the Court affirmed a patient's constitutional right to refuse medical treatment, including artificial feeding and hydration.

The Cruzan case highlights the importance of leaving written instructions -- living wills and durable power of attorney documents -- for relatives and doctors to follow in the event of incapacitating and terminal illness, said Thad C. McCanse, court-appointed guardian for Nancy Cruzan.

On Dec. 14, a Missouri judge, reconsidering the case in light of the Supreme Court ruling and new testimony, authorized withdrawal of the feeding tube. She died 12 days later, of dehydration.

"This is how millions of people died before the introduction of artificial feeding tubes," said neurologist Cranford.

The Cruzan case was not the only right-to-die case in the news last year. Under very different circumstances, a Michigan doctor helped a woman suffering from Alzheimer's disease commit suicide in June by an intravenous injection of lethal drugs. The doctor, Jack Kevorkian, was charged with murder last month, but the charges were thrown out by a judge who said the patient took the action that killed her.

What the Kevorkian and Cruzan cases both reflect is the increasing difficulty of defining quality of life in patients with devastating illness -- and the tendency of such medical decisions to wind up in court.

Spurred in part by the Cruzan decision, Congress passed the Patient Self- Determination Act, requiring hospitals and nursing homes that receive federal funds to explain to patients their right to refuse medical treatment. The law will take effect in November.

"Because of Nancy," said the Cruzans in a statement released after the court ruling in their favor, "hundreds of thousands of people can rest free, knowing that when death beckons, they can meet it face to face with dignity, free from the fear of unwanted and useless medical treatment."