By Michael Mosley
Presenter, Blood and Guts: A History of Surgery
Twenty-eight year old Kathryn Proctor, a florist, had been having epileptic fits for about four years.
"It started off with eye spasms - they were actually seizures and they developed into full fits.
"The fits can be controlled with medication but they found a lump on my brain and there's a 50% chance that it's causing the epilepsy.
"It's on the right-hand side, about halfway up on the frontal lobe."
The lump they found was a cavernoma, an abnormality in one of the veins in her brain. It had to come out, not only because it was triggering fits but because it could haemorrhage.
Kathryn agreed to let us film her operation as part of a series I was making, Blood and Guts: A History of Surgery. In fact she not only agreed, she was enthusiastic.
"I would be happy for you to film because I want to sit down and watch it with my girlfriends afterwards"
Kathryn was well aware that the operation she was about to undergo was complex and risky. Potential complications included heavy bleeding and, when removing the cavernoma, accidental injury to parts of her brain. Because of this she had to be operated on while fully awake.
The operation was performed at the National Hospital for Neurology and Neurosurgery in London by leading neurosurgeon Andrew McEvoy.
Mr McEvoy and his team were assisted by a computer-guided system called "Stealth". "Stealth" enabled them to map out exactly where the cavernoma was so, unlike early neurosurgeons, they were not be going in blind.
I found it very strange being in the operating theatre, watching Mr McEvoy carefully removing the top of Kathryn's skull while she continued to chat happily away with us.
Is there part of the brain responsible for obsession with football? And can you can remove it?
Kathryn Proctor, patient
"Is there part of the brain responsible for obsession with football? And can you can remove it?", she asked. "Yes", Mr McEvoy replied, "but you can't remove it in boys without killing them"
A 100 years ago the brain was considered by many surgeons to be too complex and risky to operate on.
One of the main problems was the extraordinarily high risk that the patients would bleed to death on the operating table
The brain has over 600 kilometres of blood vessels, and uses nearly a litre of blood every minute. Just cutting through scalp and skull often led to a fatal bleed.
The surgeon who changed this was an American called Harvey Cushing. In the early 20th century he pioneered a range of techniques that brought mortality down from over 70% to less than 10%.
While opening the skull Andrew had to proceed very carefully, using some of Cushing's techniques, such as clamps and clips, as well as more modern diathermy and drugs.
When Mr McEvoy peeled back membranes and revealed the top of Kathryn's brain for the first time it was a very moving moment.
The brain looks gelatinous and I know from previous experience that it is soft to the touch, like cold tapioca pudding.
Just looking at it you'd never know which parts did what, and that again was a problem for early surgeons.
When they were operating, trying to remove a tumour or perhaps a foreign body, they might inadvertently remove a vital part of the brain. Even if they survived, patients were often left incapacitated and partially paralysed .
To identify precisely the areas of Kathryn's brain that control sensation and motor skills Andrew began stimulating it with an electrode. Katherine remained cheerful until Andrew touched part of her brain right alongside the cavernoma, making her face twitch.
"That was my face", she said in a distressed voice, "It upsets me because it's my face"
Mr McEvoy hastily reassured her, "Sorry, but we know now where to tread carefully", before explaining to me exactly what we were looking at.
"This area here moves the hands and arms. This area moves the foot.
"And then as I came up behind the cavernoma, we found an area here that caused contractions in the face. And nearby was an area that was obviously causing eye deviation.
"That's interesting because she reports that's her seizures start with eye deviation"
Keeping well clear of danger areas Mr McEvoy removed the cavernonoma, the cause of all Kathryn's problems. It was the size of a pea.
The whole operation lasted just over three hours. I left the theatre feeling moved by the skill and compassion of the team.
I was also profoundly grateful for all the pioneers, on either side of the knife, who down the years have added to our surgical knowledge and made such an operation possible.
I'm happy to report that Kathryn has since gone on to make a full recovery.
Blood and Guts: A History of Surgery starts on BBC Four at 2100 BST on Wednesday 20 August.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.