Dr. Jules Lodish welcomes visitors to the downstairs bedroom of his Bethesda, Md., home with a robotic greeting that bursts from his computer's speaker.
Ten years of living with amyotrophic lateral sclerosis, or A.L.S., a progressive, paralyzing disease, have stilled nearly every muscle; he types with twitches of his cheek, detected by a sensor clipped to his glasses.
But ask him how he feels about his life, and Dr. Lodish, his eyes expressing the intensity denied to his body, responds: "I still look forward to every day."
A.L.S., or Lou Gehrig's disease, is often described as a kind of living death in which the body goes flaccid while the mind remains intact and acutely aware. The prospect of being trapped in an inert body and being totally dependent on others drives many sufferers to suicide.
When Attorney General John Ashcroft attacked an Oregon law allowing doctor-assisted suicide in 2001 - a case that is still working its ways through the legal system - patients with the disease were among those who supported the law in court.
But while the legal case and much of the national attention has focused on the issue of the right to die, less is known about those patients who want to live, and, like Dr. Lodish, will go to extraordinary lengths to do so.
With adequate medical care, patients often can live for years relatively free of physical pain from the disease itself. "It's more a sort of existential, psychic sort of pain," said Dr. Leo McCluskey, a neurologist in Philadelphia who treats many people with the disease.
As a result, patients and their families are forced, on a daily basis, to take stock of the meaning and quality of their lives and to make repeated decisions about how much is too much.
"With A.L.S., you have a choice about when to stop treatment," letting nature take its course, said Dr. Linda Ganzini, a professor of psychiatry at Oregon Health and Science University in Portland, who has studied patients making end-of-life decisions.
What keeps many patients alive, experts say, is a sense of having unfinished business - perhaps a milestone "like getting the last kid off to college," said Dr. Mellar P. Davis, a professor of hematology and medical oncology at the Cleveland Clinic.
Those patients who do best are those who have insurance that covers nursing and medical care, allowing them to avoid some of the major health risks associated with the disease, and family members who can cover the hours when expert help is unavailable.
Many patients, Dr. Ganzini said, have deep religious beliefs that help sustain them, and they are able, "to find hope in the future, find meaning and tolerate the daily ongoing losses that they are experiencing."
As Dr. Davis put it, "Quality of life becomes a moving target - what was one day an unacceptable quality of life becomes an acceptable quality of life."
Dr. Lodish's body sits limp in a wheelchair and his tongue lolls; a machine breathes for him through a tracheostomy tube in his throat. He lost the ability to talk more than three years ago, he says, then jokes, "but not the ability to be annoying."
At a time when even business executives fall into the shorthand of teenagers' text messages - "r u going 2 the mtg?" - he refuses to cut corners, communicating in eloquent sentences in person and via e-mail.
There are no half measures for Dr. Lodish, a hematologist and oncologist who devised his own intricately detailed treatment regimen. He wrote a 30-page guide for his nurses that sets standards for a sterile environment that go beyond hospital practices, rules that have helped him avoid the infections that kill many patients.
When he could no longer eat, he did the research to come up with a recipe for the nutrient blend that flows down his feeding tube - even determining that the ingredients were kosher - and he typed the two-page guide to its preparation, twitch by twitch, with a special program on the laptop that helps him to choose whole words or phrases from scrolling lists.