The boy with half a brain

Harrison was unconscious for three days

A remarkable operation in which a severely epileptic child had half his brain removed is chronicled in a BBC documentary.

The radical surgery not only improved Harrison Ward-Mullis' epilepsy, but did not have the catastrophic effects on his brain power that some doctors might have feared.

His story, evidence of the amazing power of the brain to adapt under pressure, is told in "Brain Story" on Tuesday.

The left hemisphere was badly damaged

Harrison, now six, suffered a burst blood vessel on the brain when a baby, but the devastating effects on the left hemisphere of his brain were not fully evident until some time later.

He developed a form of epilepsy which, while not producing the "grand mal" convulsions normally associated with the condition, involved an almost constant disruption of his brain function.

Monitoring the activity in his brain revealed almost constant "little storms" of electrical discharges which severely hampered his development.

His mother, Jackie, told the documentary: "We used to tell people: 'My son has epilepsy', and they would say: 'He looks alright to me'.

"He would sit there rocking backwards and forwards for about an hour. He would be very aggressive."

Scans revealed that the entire left hemisphere of the brain was horrifically damaged - doctors believed that this malfunctioning half was sending constant, uncontrollable electric discharges into the good half.

Radical removal

Some severe epileptics do have smaller parts of their brains removed to try to limit the seizures, but Jackie agreed to an even more dramatic solution - the removal of the entire half.

She said: "The big thing for me in deciding whether to have the surgery was the fact that at any given moment, I could have lost him in a seizure anyway."

Jackie Ward-Mullis decided to risk the operation

The main concern of the doctors was that the left hemisphere controls many of the vital activities of the brain, including speech, and the movement of the right side of the body.

After the operation, Harrison was unconscious for three whole days.

However, as soon as he awoke, it became clear that his brain had been very busy.

He was able to speak in almost complete sentences - possessing more ability than he had managed prior to the operation.

In those three days, the brain had managed to reorganise itself so that the right hemisphere could take on the speech-controlling role.

"Brain Story" will be broadcast on BBC2 on Tuesday at 2200 GMT/2100 BST.