Over the years I have met many authors who have submitted to being interviewed with barely disguised reluctance.

Some answer languidly, as if waiting for their interest to be piqued by a question no-one has ever posed before. They are not rude, precisely, but their boredom is poorly concealed. Others are a little too eager and babble incontinently, rattling on without allowing you to ask more than the opening question, the answer to which takes the entire time allocated. A few are outright hostile, and even more are nervous or suspicious.

Only once, however, have I met a writer who was so shy he could not look me in the eye. That was Oliver Sacks. Author of Awakenings, and The Man Who Mistook his Wife for his Hat and other bestselling books about people with severe neurological disorders, he is one of the world's most famous and feted doctors. One might have assumed, therefore, that he would be unfazed by a short conversation about his latest work, but one would have been wrong.

Ushered into his bland room in a London hotel, I recall sitting at a table opposite him. His back was to the window, and he had the air of a trapped animal. And in some ways he was. Both of us knew I would not be leaving until the tape-recorder had been well fed with quotes. Dutifully he replied to questions, but although he occasionally broke into laughter, he stared at the table the entire time he spoke.

Sacks has described his shyness as "a disease". He has never married, or lived with anybody, and yet, when he disclosed recently that he has been diagnosed with terminal cancer and has only a short time left to live, it was not at all surprising to see him describe himself as grateful for being loved. Quite apart from his friends, tens of thousands of readers who have never met this most diffident of doctors feel affection for him. It could even be that his bashful, hesitant demeanour has helped him win the confidence of those whose conditions he has treated and written about with such respect and fascination.

Sacks made his name with his account of patients in a Bronx hospital suffering from encephalitis lethargica, whose decades-long catatonia he briefly lifted with the drug L-Dopa. Subsequently he wrote about the small army of people he has met with a range of neurological complaints, from Tourette's syndrome to colour blindness. In all these books Sacks adopted the technique of 19th-century doctors in describing a patient's case history in great detail. Readers loved these stories, but the medical fraternity was sceptical, some considering his anecdotal approach unscientific and subjective. As one jealous rival wrote, Sacks "is a much better writer than he is a clinician".

Those of us who lapped up his tales, however, disagreed. Sacks represented the compassionate and approachable face of a medical profession that, as technology advanced, increasingly treated a patient as a specimen rather than an individual, a statistic rather than a face. In contrast, Sacks was aware that everyone he met on the ward was unique. Those who feared the anonymity of the medical conveyor belt or the clinical coolness of the consultant and his cohort thus found comfort in knowing that beneath the white coats some doctors were also interested in the person as well as their disease.

Of all the scientific professions, medicine seems the one that most often throws up gifted writers, as if the talents necessary for diagnosing illness are akin to the perception and precision literature demands. Too committed a writer to give up in the face of his detractors, Sacks thankfully continued to pursue his dual career. The result is the belated introduction in certain medical schools of what is termed "Narrative Medicine" as part of neurologists' training. Largely because of Sacks, the full case history is once more seen as an important aspect of treatment. One hopes his critics are chastened.

On revealing his own prognosis, Sacks confessed that he takes solace from one of his favourite philosophers, David Hume. Realising he was dying, Hume dashed off a short memoir. As the neurologist writes, "one line from Hume's essay strikes me as especially true: 'It is difficult,' he wrote, 'to be more detached from life than I am at present.' Over the last few days," Sacks continues, "I have been able to see my life as from a great altitude, as a sort of landscape, and with a deepening sense of the connection of all its parts."

It seems rather ironic that the doctor who made his name by taking a bird's eye view and understanding the bigger picture for his patients, is only now doing the same for himself.