Now 17 he is described by his mother, Ann Maxwell as "profoundly disabled". He needs 24 hour care and struggles to communicate.
Mrs Maxwell said: "Muir has seizures all the time, but you cannot always see them. It is the seizures we cannot see which I think are more damaging."
She and her husband set up the Muir Maxwell Trust in 2003 to provide support to others affected by epilepsy. It has since raised almost £8m and funded a DNA service at the Royal Hospital for Sick Children in Glasgow so families no longer have to rely on services in Australia.
Mrs Maxwell said when she first heard the notion of giving children a cannabis extract to help their symptoms she thought it was ridiculous, but after talking to experts became convinced that clinical trials were needed.
Mrs Maxwell, 50, from Midlothian, is not planning to enter Muir into the UK tests if they go ahead. "My aim has always been to try to make sure that the outcome is better for children who are following behind Muir," she said.
However, she continues to hope life-changing treatments will be found.
About her own son, she said: "There is a boy in there waiting to get out."