An 11-year-old girl with cerebral palsy has made a "huge improvement" since undergoing pioneering stem cell treatment in the US, her mother said.

Holly, from Huntingdon, Cambridgeshire, was deprived of oxygen at birth, leaving her movement, balance and speech impaired.

Her family paid £10,000 for stem cells to be injected, with the idea being that they would multiply in the damaged part of Holly's brain.

Fiona Greenhow, her mother, said Holly was now sleeping longer, had improved vision, an expanded vocabulary and more control over her muscles.

"To suddenly see some tiny little steps is wonderful and it just gives us hope for what might happen in the future," she said.

The National Stem Cell Foundation said the "complex science" had yet to go through clinical trials and there were potential risks.

The range of treatments Holly is receiving makes it difficult to know which to attribute the change to, it added.