£60,000 aim for a life-changing operation to get Shrewsbury's little Isla walking

But she also faces challenges that many adults would struggle with.

Today her parents Jonathan and Lai-Chen Marshall, who also have another daughter, Thea, aged nine months, spoke of their campaign to take her to America for an operation to help her walk.

The surgery is not available on the NHS so they are faced with having to raise £60,000 for the operation across the Atlantic to help ease the effects of the condition spastic diplegia, a relatively rare form of cerebral palsy.

Mrs Marshall said: "She was about two-and-a-half years old when she was diagnosed with spastic diplegia.

"We thought that something was wrong as she was not reaching her milestones such as crawling and walking and we saw a number of doctors and specialists before they reached the diagnosis.

"At the time, there was a trial being done on the NHS to treat her condition.

"But the trial has now ended and although we could do it privately here, we would prefer to take her to America where she can be treated by a doctor who has done the operation for a number of years and has made it a real speciality of his."

Spastic diplegia means the muscles in both Isla's legs are continuously contracted, forcing her to walk on her toes.

Due to the spasticity, or tightness, in her legs, Isla has poor balance and frequently falls over. She finds daily tasks such as walking up and down the stairs, dressing and walking on uneven ground very difficult.

She also finds it hard to keep up with her friends at pre-school.

"There is a tightness in her legs which is caused by her nerves telling her muscles to tighten up all the time.

"She walks on her tiptoes and does not have very good balance," said 30-year-old Mrs Marshall, who lives in Copthorne and works at the Royal Shrewsbury Hospital as a sonographer."

Traditional treatments include leg braces and intensive physiotherapy. But there is also the developing technique of surgery that targets nerves which are causing the problem.

Mrs Marshall said: "The surgery will test all of the nerve roots and then get rid of those which are causing the problem.

"This operation has had very good results and the surgeon in Missouri is one with the most experience."

The treatment is not offered on the NHS through a ruling by the NHS body Nice, which decides which areas of medicine should be free to patients.

The money raised will not just pay for the operation but also for the follow-up care that Isla will need such as physiotherapy and after care.

"It sounds like a large amount but it is for all the care Isla will need afterwards," said Mrs Marshall, whose husband Jonathan, 32, works as a train driver.

"This will be done in the UK. We just want to get it done as soon as possible which is why we have launched the appeal to raise the funds.

"It is a lot and I am not sure how long it will take us to raise the money.

"We have people who have offered to run 10k or marathons. It is just starting to gain momentum so I am hopeful."

• Anyone wanting to donate should go to www.justgiving.com/isla-marshall or www.treeofhope.org.uk/islas-story