People celebrate their Sundays in various ways: church, brunch, sleeping in. Neurologist Oliver Sacks once had a patient who always got a headache.

This was no ordinary little pain, but an excruciating migraine. It was an event, it was drama. The family would gather, the doctor would be summoned, children hushed.

Sacks prescribed ergot compounds, which constrict the dilated pulsating vessels in the temples that cause a migraine.

The first migraine-free Sunday, the patient was understandably jubilant. The next, he was still healthy, but less grateful. In fact, he complained of boredom, and said no one visited him.

On the third Sunday, Sacks got an emergency call. The man, who had had asthma as a child, was having an attack and needed oxygen.

This paradoxical reaction forced the attention of both patient and doctor down to a deeper level of healing, and they spent several months talking about the role of illness in the patient's life. During this time, the headaches grew much milder and the man became able to enjoy an excitement-free Sunday.

"Sometimes it suffices to make a diagnosis and give a pill," says Sacks. "But the more severe and chronic something is, the more the personal angle has to also be considered.

"You need to look at a life and a world, as well as at the specifics of the disease."

Tacked to the bookshelves in Sack's office on New York's City Island is a large "NO!" -- a reminder that, even if he is on his way to becoming a celebrity, he need not agree to all requests.

Ironically, Sacks is earning acclaim not from a self-help gimmick or a wonder diet, but because he seems a throwback to a disappearing type: the fatherly, wise, house call-making physician. Marcus Welby hasn't been seen for a while.

His highly regarded books include Awakenings, a chronicle of how the miracle drug L-Dopa was administered to patients who had been suffering from sleeping sickness for almost half a century; Migraine, regarded as a definitive work; and the current The Man Who Mistook His Wife for a Hat (Summit, $16.95). This last, a collection of "clinical tales," is wildly successful for a book that makes few concessions to the reader's lack of medical knowledge. In its seventh printing, it is on both national and Washington best-seller lists.

"I'm as quick to order a CAT scan as the next man, and I don't envy a post- or pre-technological era," says the 52-year-old Sacks, who resembles an Eastern Orthodox monk. "But if technology is with us, I think there's some danger it can be the end of medicine."

Sacks' specialty is diseases of the nervous system -- the conjunction of the mind and body, and the mystery by which the physical world becomes a mental experience. When the magic is missing, serious brain damage can result.

"The first look at patients with very gross neurological illnesses is nothing short of horror. But as soon as one gets beyond this, one gets the feeling of the spirit inside -- of human valor, and of humor and resourcefulness."

Since most people are shielded from such illnesses, Sacks observes, they have an insufficient sense of wonder and gratitude for their own lives. "We take the continuity of our lives for granted, until we encounter Jimmie," the "lost mariner" for whom time had come to a stop.

Asked what year it was, Jimmie replied: "Forty-five, man . . . We've won the war, FDR's dead, Truman's at the helm. There are great times ahead." A gray-haired 49-year-old, Jimmie was convinced "I'll be 20 next birthday;" he could not recognize people from visit to visit.

A cure for Jimmie's retrograde amnesia was impossible -- attempts to force him to confront the actual world only panicked him -- but he eventually found solace in the garden and the chapel at his home for the aged.

Another disorder is represented by Dr. P, a professor of music with an inability to make cognitive judgments, to such an extent that he could not recognize a glove ("It appears to have . . . five outpouchings") and mistook his wife for a hat (His wife, Sacks notes, "looked as if she was used to such things").

"We say with Gertrude Stein that 'a rose is a rose is a rose.' But for Dr. P it wasn't: It was a convoluted red form with a linear green attachment. Its rosiness, its rosehood, was not given to him."

Only when Dr. P was singing or humming to himself could he function normally. If he's interrupted and loses the thread, his wife told Sacks, "he comes to a complete stop, doesn't know his clothes -- or his own body."

Sacks takes obvious relish in such patients, sympathetic to their plight and alert to their survival strategies. But for most people, the elderly and the ill can be both alien and frightening.

A hundred years ago, there were few houses in which someone had not died. Now, the elderly are increasingly segregated in retirement communities or nursing homes, and many young people are separated from a direct knowledge of age and death.

"A couple of generations ago," says Sacks, "most people had an experience with some moderately serious illness themselves, and most of them had lived with grandparents and saw the frailties and predicaments of age as part of life. Many people also had been at deathbeds, which now are hidden away in hospitals behind medical paraphernalia."

Sacks does not, of course, advocate a return to a more primitive culture, but he does view with alarm a society that isolates itself from the abnormal. "If we see as wrong any deviation from youth and health and beauty, we'll lose our charity and our sense of human variety."

His first inspiration for portraying "the opposite of a freak show -- a human show" came from his parents. His mother was a surgeon; his father is a general practitioner in London who retired when he was 70, got bored, and promptly went back to work. Now 90, the elder Sacks still makes house calls, although he now hails a cab.

"My parents were both fond of telling stories of medical predicaments," Sacks says. "The house was full of medical and scientific books of my parent's vintage, and the vintage before that, which I think were more vivid and eloquent than current things. That's the tradition I was brought up in."

The migraines suffered by the young Sacks gave him his earliest instruction in neurology. There is a case history in Migraine of a "middle-aged professor, of fiery temperament, who tends to get classical migraines on Friday afternoons, following his inspired and stormy teaching sessions." The resemblance to the author isn't exactly coincidental.

"I get fired up and have to perform," says Sacks. "It's the cost to pay. But since there's little pain involved now -- just visual stimulation -- I rather enjoy my migraines."

Since these headaches can be caused by stimuli as varied as flickering lights, cheese, a mother-in-law, menstrual period or loss of temper, every patient requires an exploration as to the cause -- the origin of Sacks' approach that every patient is different.

If physicians would realize this and enter into their patients' lives, they'll never become bored or burnt out, Sacks argues. "Treating patients mechanically causes many doctors to feel they're redundant . . . Patients feel this too, and it's one of the reasons for a breakdown in relationships." And the pressures of time are no excuse: "Individual attention is perfectly compatible with speed, if things are done right."

A professor of clinical neurology at the Albert Einstein College of Medicine and staff neurologist at both Beth Abraham convalescent hospital in the Bronx and at Bronx State, a psychiatric hospital, Sacks also works at three nursing homes and maintains a clinical practice. He sees about 50 patients a week.

The initial consultation takes time, "but after that, when there is a relationship, you can very quickly home in on what's essential." His definition of "very quickly": two minutes. During this time, his ideal doctor is totally concerned with the patient, and the patient knows it. The result, according to Sacks: a feeling by the patient that he or she has all the time in the world.

Dr. Michael Kremer, Sacks' former chief at Middlesex Hospital in London, wrote a paper about how much doctors could perceive as patients entered the room: from their faces, their postures and movements, the ways they sat down.

"An immediate picture was formed for him, before the examination had even begun," says Sacks. "It's like being a detective. From the peculiar and special nature of the patients, you've got to put clues together."

These facts are assembled in his copious notes, which total as many as a million words a year. Fond of places where he can walk with a notebook, the neurologist does his writing in the Bronx Botanical Gardens and at a favorite lakeside hotel in a nearby county.

"My notes are existential as well as neurological. I want to grasp and express the whole situation as best I can," he says. "This is what being a doctor means."

Sufferers from Parkinson's disease, a degenerative muscular ailment, sometimes can't take a single step. If they could, they will then be able to keep moving; but they're frozen.

"They may find that if they carry some paper with them, and then drop it, they can step over it," says Sacks. "And having stepped over it, they can then walk."

Patients may have a further revelation: it's not even necessary to drop the paper, but just to imagine doing so.

"Resourceful patients discover this themselves, and it's one reason to respect them more, and let them volunteer things. The essential thing here, on all sides, is understanding."