A terrifying series of seizures meant Chris Holdridge had to undergo major brain surgery. It not only saved his life, but altered it for ever

When I woke up in the ambulance, the first thing I saw was my boss, Elaine, holding my hand. "You've had a bit of a turn," she said. "We're just going to get you checked out."

One minute I had been sitting at my desk at Radar, a TV production company in east London, where I worked as a researcher, the next my body went stiff, my eyes glazed over, and I dropped to the floor, shaking violently from head to toe. After several minutes I lapsed into unconsciousness. Waking, I felt utterly confused.

It has been said that seizures are like running a marathon in two minutes and I can believe it: my legs and arms were like dead weights and I could barely raise my head.

After a few hours at the Royal London Hospital, a doctor appeared. He was about my age, mid-twenties. He explained the likely diagnosis - epilepsy - and told me that this is a general term for any condition which gives rise to seizures. Exactly what was causing mine was a mystery that further tests would help to solve. The second he was gone I had what some describe as a "lightbulb moment". Something just lit up inside my head like a big cartoon thought bubble, reading: I could do that.

Over the coming weeks I had tests, including an EEG, where the electrical activity of the brain is monitored, and an MRI scan, in which an detailed image of the brain is created. The neurology consultant, Oliver Cockerell, told me that the tests indicated an abnormal vessel in my brain, a cavernous haemangioma, or cavernoma, which has very thin walls that allow blood to leak into the surrounding tissue, causing a misfiring of electrical impulses and leading to seizures.

Since my first trip to A&E I had suffered several more fits, all at night. These were much scarier than the first: I would wake up alone and bewildered. My memory would be shot with holes, like Swiss cheese. I would not know what had happened to me, and there was also a weird feeling of not quite knowing who I was. It was a feeling of elemental terror.

Dr Cockerell decided to put me on Tegretol, an anti-seizure medication. He also told me that the law required me to surrender my driving licence as there was a risk I could seize while driving. It seemed I was destined to be on the Tegretol - and on the bus - for the rest of my life, but Dr Cockerell wanted me to speak to a neurosurgeon.

John Wadley explained that as the cavernoma was near the surface of my brain he could excise it. He warned me that although this was a relatively uncomplicated procedure, brain surgery is never 100 per cent safe; there is always the risk of paralysis.

Although the risk was small, the idea of paralysis gave me many sleepless nights. But after a great deal of soul searching, I decided to trust the surgeon's instincts.

The day for my operation came and I checked myself into Sofia Ward. A doctor attached rubber suckers to my head and drew round them in purple marker pen to guide the drilling equipment.

The next day I was taken down to surgery. Once I was under the anaesthetic, Mr Wadley removed a section of my skull, excised the cavernoma and refitted the skull portion with titanium screws. When I woke up, a nurse was dabbing my head and I could see Mr Wadley taking off his surgical gloves. I couldn't stop crying. It wasn't so much relief - it was more that my emotions were so close to the surface; the tears just kept pouring out. The theatre nurse was stroking my head and squeezing my arm, and every time she squeezed, she squeezed out more tears.

Back on the ward, I caught a glimpse of myself in the mirror. Half my face was bright yellow, and my eye was black, purple and blue. I had a huge bandage wrapped round my head like a lobotomy patient and a blood-filled drain hanging from the side of my head. Peeping out from under the bandage I could see a row of surgical staples like a train track. I was exhausted, but every couple of hours a nurse would shake me awake and ask me my name, the name of the Prime Minister, the date, and where I was to check for brain damage.

After a few weeks of recuperation I was firmly on the mend. The operation had been a success, but I knew that my life was never going to be the same - my experiences had thrown a few things into sharp focus and I knew I wanted to make some changes - specifically, I wanted to change career.

Since I was hospitalised at the age of 10 with asthma I had always admired the skill of doctors and had wanted to be one. Unfortunately, when it came to choosing my A-levels I eschewed hard science for EM Forster. From there it was an easy passage to an English degree, but there was always a nagging doubt that there was something I'd forgotten to do. But even if I had answered that nagging voice in my head, surely it was too late?

With my condition throwing my priorities into sharp focus, I began to question this assumption - what if it wasn't too late? I had heard of accelerated, graduate-only medical courses, and now discovered that several of these are open to graduates in any subject, and can create a competent doctor in only four years.

The downside? These courses are horrendously oversubscribed. In 2005 the applicant-to-offer ratio for the graduate course at King's College, London, was 56:1. Some 1,350 applicants applied for 24 places. At St George's med school in south London, the figure was a little better, but still - 20 applicants for every one of their 70 places.

With a due sense of dread I registered for the entrance exams and, shocked by the difficulty of practice papers, began to spend my every spare moment studying stoichiometry, thermodynamics and 3D stereoisomerism. Now at the BBC, I would sneak off in my lunch hour to a rarely used meeting room to get stuck into the textbooks.

As soon as I was fit enough, I also began working as a volunteer in an A&E department. I met some real characters, including Beryl, a frail, elderly lady with suspected MRSA and a disarming fearlessness. On one occasion, she looked me straight in the eye and said something I'll never forget: "Isn't it a shame we can't choose when we're ready to die." I have never been so stumped for something to say, but it was experiences like this that most excited me about medicine - it's a world of big moments and crises, of hope and despair, of life and death.

After eight months it was time for the entrance exams. My only chance of an interview was to get a mark in the top 10 per cent of applicants. To my total stupefaction, I came in the top 5 per cent and proceeded on to the interview stage at three schools. At each interview I told the story of my illness and how it had brought home my profound desire to practise medicine. I received offers from every school I applied to, and accepted a place at King's, where in a week's time I'll begin examining patients and performing dissections almost from day one.

It's now more than a year since the operation and I haven't looked back. In some ways, it's as though my cavernoma never happened, and yet it has changed my life: I'm now going to be a doctor rather than a TV producer, and I'm also no longer single; after my EEG I sent a Valentine's card to the pretty neurophysiologist who ran my test and, amazingly, got a date out of it. Sian and I have now been together 18 months and last weekend, we moved in together. I have so much to be thankful for, and it's all down to a tiny mischievous blood vessel in my brain. If that blood vessel were a man, I'd buy him a beer.

Seizures: facts and figures

* Epilepsy is defined as the tendency to have recurrent seizures. It affects one in every 131 Britons.

* Seizures occur when the brain's neurons misfire, disrupting the normal signals between brain cells.

* Some people will have epilepsy because of brain damage, but in many cases the cause is unknown

* Most people with epilepsy are treated with anti-seizure drugs.

* Only a small proportion of people with epilepsy will benefit from neurosurgery. This can only be considered if the seizures can be shown to originate in one area of the brain.

* For more information visit www.epilepsynse.org.uk