WATCH Malcolm Shaw's report
He spoke to Caity and Angelina, Caity's mum Paula Harman, Cognitive neuropsychologist Dr Ashok Hansari and Lisa Massingham, Angelina's mother.
Imagine the shock of being told the only way to control your child's epileptic seizures is to disconnect half their brain.
But that was the prospect facing the parents of Caity Downs from Brighton and Angelina Mills.
The drastic surgery was performed on them when they were toddlers, transforming their quality of life.
The girls have Sturge Weber syndrome, an extremely rare neurological condition that can trigger life-threatening epileptic seizures.
But the two friends haven't let that stop them living their lives to the full. The girls have just completed a sponsored walk of almost two hundred miles, ending in Brighton.
For more information on the girls' charity click here