After many weeks in a hospital bed, a man wakes up and surveys his room. He tries to focus on the people standing there, before speaking to them while they fuss. But no-one is listening. His voice, at first quiet, turns to a shout and then, inevitably, a scream. Still they ignore everything he says. Inert and disoriented, he tries once more to tell them to move his legs to a more comfortable position and adjust his arms. They ignore him again. So he shouts at them to leave the room. Nothing. Finally, exhausted, he falls asleep, chilled by the realisation that, while his mind still works, his voice has gone. He is silent as snow underfoot. This man is my father.

Six years ago, on January 21, 2002, my father suffered a stroke - "a spontaneous intracerebral haemorrhage". In layman's terms, the pressure in his head simply got too much and a valve blew, leaving a path of destroyed brain tissue in its wake. The only way to deal with it was to cut out the malignant part (the dent in my father's head is above his left eye). Part of my father went with it. Since the first incision, he has been pushed and pulled out of shape and become, in effect, someone else. He is now wholly dependent on both his family and a small army of carers for virtually everything in his life. He has dysphasia, a condition characterised by a complete or partial loss of ability to understand, speak, read and write.

My father, who is 64, is now in the foothills of becoming elderly. He can still, we suspect, think clearly and know what he is feeling, yet talk with him and you receive little apart from an occasional, abbreviated sound. But a minuscule fragment of my father is still my father. For all this, he is the hub which our wheel of experience revolves around. At my parents' house, his dedicated carers winch him up on a hoist and move him into his wheelchair to begin or end his day. When I visit, I usually find him sitting nobly in his green chair, fingertips to temples, waiting to be moved once again. His grin has a certain beauty. Then my father locks me in a gaze. But the words are hammered tight inside. Frustration etches his face when I explain, once again, that I just cannot understand what he's trying to say.

In the past we were able to shuffle him from chair to chair. Now this is no longer possible as he can not stand at all. And my mother, his primary carer, no longer has the strength to hold him. So the carers have taken over his life. Each carer, in his or her own small way, makes the indignity of the task a little easier with ready conversations and jokes. While the cycle is remorseless, it is gratifying that there is always someone willing to guard and protect the sick.

In 1995, Jean-Dominique Bauby was the 44-year-old editor-in-chief of French Elle; a father of two young children, known for his passionate approach to life. By the end of the year he had suffered a stroke and, following 20 days in a coma, awoke to a body that had all but ceased functioning, apart from one eye. His mind remained unimpaired and, by blinking, he was able to dictate a book - The Diving Bell and the Butterfly - recounting his experiences by selecting each letter of the alphabet. The diving bell represents his locked-in condition while the butterfly is his soaring spirit.

The locked-in life of Bauby, whose story has now been turned into a film, mirrors so much of the catastrophic experience of my father. The anger, regret, sadness and love that the author was able to express in his book also mirrors my father's feelings. To watch the film, and see Bauby returning to the "inexhaustible reservoir of sensations" that keeps him in touch with himself and the life around him, is heartbreaking. So it is with my father. His world of communication revolves around a few indecipherable grunts, smiling and moments of complete quiet. He also talks with his eyes, his ready smile and through moods that can be as pungent as waxy, red apples.

Every day he points, with shaking fingers, at adverts in newspapers and on the television for the latest computer or camera (none of which he can use). He cherishes his new phone and watch. Small things that help him haul some of his old self from the past, like a lost battleship at the bottom of a murky ocean.

The human brain is an extraordinary and colossal, energy-hungry organ, using more than 20% of the body's blood supply to survive. By the time all of its 100 billion neurons, or nerve cells, have been developed and it reaches adolescence, the brain - the body's "computer" - is filled with incalculable human experiences: sensory reasoning, language and social skills. By the time the brain is around 40 years old (my age on my next birthday), it is already beginning to shrink.

In a few more years, high blood pressure, cholesterol, smoking and other diseases affecting the blood supply to the brain can lead, ultimately, to a stroke. According to the Stroke Association, in the UK each year there are roughly 150,000 strokes and, while most people affected are over 65, anyone can have a stroke, including children and even babies. My father was only 58. Unlike Bauby, he can move most parts of his body with a little perseverance. He can shave with shaking hands, and he can eat his dinner in his chair with the same shaking hands. Like Bauby, the lesson of my father's stroke is one without a plot or a simple narrative. It is meandering and reminiscent. It often has no points to make at all. Yet his life is filled with beautiful anecdote and detail. It is a rich thing.

There is a crushing scene in the film where one of Bauby's children wipes a sliver of saliva from their father's unmoving mouth. It is powerful and intimate. And something each of my family does constantly.

Throughout the past six years my mother has been his strength, weathering all his personal storms. They met in 1962 in Crinan, Argyle, where my mother worked as a housemaid and my father was a visiting electrician. She was almost 20, my father 19. Their first date was at a cinema at Lochgilphead, and my father picked her up on his Norton motorbike. A few months later she moved back to Glasgow. They had only been going out for a year when my father asked her, in a cafe in Byres Road, to marry him. They married in June 1966 and had their reception in the Ca' d'Oro on Union Street, before honeymooning in Blackpool.

They talked about the future and had nine children. Neither could ever have envisaged the awfulness of what a stroke can do. One look at photographs of my father in the summer before his stroke compared to now tells its own harrowing story. His former self seems to have died a lonely death and the man left behind in his place is a slightly abstract version of the one before. Once, he was as strong as a coal wagon; now he is as weak as a child.

There remain so many unanswerable questions. When did his stroke take root? Why did it strike when it did? Why him? A stroke and its aftermath can be terribly debilitating and lonely. But each day brings a new memory to the surface. A six-year march in a voiceless desert means we are forced to remember fragments of memory with him - the sound of a Volkswagen engine, home-made tomato soup, the loft, re-soled shoes, oose-covered sweets in a jacket pocket and Radio Telefis Eireann. If I live to be a hundred, I will never forget the sight of my father working on his old Volkswagen van. There was always something wrong. But he could always bring it to life.

His own life has reverted to routine and there is a great deal of comfort in this. How we used to love conversing with each other. And how I love his daily attempts to converse with us - my mother, brothers and sisters. Words of comfort in this long corridor of silence, to say that he is all right. I was in awe then, as I am now (I still reach out to tap the metal of a parked Volkswagen van). His brain haemorrhage, destructive as it was, cannot break the spell of memory.

Although my father's body is weighted as an anchor, like Bauby's, his mind soars like a butterfly through time and space. My father is the immobile hero fated to suffer in this world of silence. And I know that if anyone has the strength to endure it, he can. How I love writing those celebratory words. But, like most things that we try to do and say to each other, it is, inevitably, belated. That is the hardest part. That I had never thought to write more about him before.