Seven-year-old Hallie Campbell from Wigan doing well after brain surgery in Poland

This time last year little Hallie Campbell from Wigan was unable to walk, talk or even sit up by herself. She was also suffering daily painful seizures which often went on for hours at a time.  She'd been born with an incredibly rare genetic brain condition called AADC deficiency.  A bit like Parkinson's disease, it left her effectively locked in her own body.

The first time I met Hallie back in August last year, her family was desperately trying to raise £70,000 for a brand new treatment being offered in Poland.  It was so new, it was actually only still being trialled but Hallie's family felt it was their only hope of transforming her life.

I remember that first meeting with the family very well.  Despite how desperately ill Hallie was, she still had the most amazing smile.  But within minutes of us arriving and beginning to film, she suffered one of her daily seizures and I saw first-hand the distressing reality that she had been living with for the last 6 years.  

Her story had such a response when we aired it on Granada Reports that hundreds of our viewers, complete strangers, felt moved to donate to the family's fundraising campaign. In just a few short weeks, they had reached their target and we followed them to Warsaw in Poland where she underwent pioneering gene therapy surgery.  We were given exclusive access to film the whole procedure, as Hallie became only the 8th child to have the operation in Poland.

Hallie Campbell after gene therapy in Poland Credit: ITV

It was risky surgery - brain surgery to be precise - where neurosurgeons drilled into her skull and replaced a faulty gene in Hallie's brain to encourage her body to start producing an enzyme she's deficient in.  The operation appeared to go well, but the treatment was so new, her prognosis was uncertain, and no-one knew how effective it would be.

Well fast-forward 10 months and I went back to visit Hallie and her family, to see just how she was doing.  And as I walked into their back garden, I couldn't quite believe my eyes.  This little girl, who when I last saw her, was in a wheelchair, locked in her own body, was there on a garden chair, sitting up all on her own, smiling that huge smile and waving at me.

The transformation was quite extraordinary.

And that wasn't it.  As she grabbed hold of one of her books, she actually spoke.  "A book" she said.  And just like a baby begins to reach each new milestone, Hallie too is learning all those lessons that most of us take for granted.

Hallie Campbell 10 months after gene therapy Credit: ITV

Her family say they never expected this transformation, and the speed with which she has improved.  When they began their fundraising campaign, it was called 'Hope for Hallie'.  They simply wanted to provide a chance of a new life for their daughter.  What this surgery has achieved is beyond their wildest dreams and the improvements are continuing.  She's begun learning how to walk with a walker and they're looking forward to every new milestone that she makes.  

This won't cure her AADC deficiency but they believe this operation has tranformed her quality of life immeasurably.  The trial of this gene therapy is still ongoing in Poland but the doctors behind it are hoping in the future this treatment could extend far beyond Hallie's rare condition, and patients with other Parkinson-like disorders could also be helped. And in a world short of positives right now, that is certainly a prospect that is extremely exciting.