A mother's agonising decision to sacrifice her son's memory and speech.

Charlotte Caldwell is prepared to do anything to keep her little boy alive, even if it means sacrificing his memory and ability to talk.

Sadly, that will be the result of the invasive brain surgery 11-year-old Billy needs to put an end to his life-threatening intractable epilepsy.

Speaking to a local radio station, the Irish mother of two said she has struggled to come to terms with the decision to let him go under the knife, but is now convinced it’s the only option.

“After much thought, it’s the lesser of two the evils, because if he doesn’t have it done, the inevitable, the unthinkable, is going to happen to him,” she told Cool 97.4FM.

Billy and his mum, Charlotte. Image: Facebook.

Billy's condition first presented itself when he was just four-months-old, and within weeks of his first seizure the otherwise healthy little boy was suffering up to 100 per day.

Doctors had little hope. Having given Billy a life expectancy of six months, they offered to administer a high dose of morphine, which would allow him to slip gently away. But the Charlotte couldn't allow her son's final moments to be lived in a hospital.

"Completely numb and devastated I took my wee Superhero home to die," she wrote on a fundraising page. "I bathed him, massaged him and wouldn’t leave him, not even to go to the bathroom."

Billy has been treated by doctors in the UK and the US. Image: Facebook.

During those torturous hours, she researched extensively online and found an American specialist, and a glimmer of hope.

She raised the near $400,000 required to see the Epileptologist, and within three months Billy was being treated in Chicago, taken off a cocktail of drugs and put on a Ketogenic diet. It was a plan that seemed to work - the seizures subsided, and he had the time and freedom to undergo physiotherapy and treatment to make up for the developmental delays caused by his condition.

The little family had eight years of breathing space, until a few months ago.

The seizures returned with a vengeance, leaving Catherine "heartbroken".

"When he [has a seizure] I have to administer 12.5 mg diazepam PR and put oxygen on him as he goes blue. One seizure can take his wee life or leave him disabled again," she wrote.

Each morning the first thing Catherine does is check her "little warrior" is still with her, still breathing - "And then I close my eyes and pray, thank God you have survived another day. I get to keep you one more day."

Their hopes now rest on the invasive, life-altering surgery offered by the US specialist. But at nearly $500,000, she needs the public's help, and has launched a fundraiser via Just4Children.

“We were told he would barely turn one, never mind be alive a decade later," she wrote. "The fact he is still here and come so far is even more reason to try and get him the best treatment possible."

You can donate to the 'Keep Billy Alive' campaign here.