A nine-year-old car crash survivor has defied medical odds, recovering from horrific injuries that could have killed him.

Seth Gilford was just six years old when the car he was travelling in was involved in a terrifying smash and rolled off the highway near Swan Hill, in Victoria's north.

His father, also a passenger in the car, was killed and the female driver jailed for six years for manslaughter.

Seth suffered shocking injuries which saw him spend seven months at the Royal Children's Hospital, with his nana, Wanda Petersen, at his bedside throughout his recovery.

She said doctors did not give much hope for the future, predicting Seth would spend the rest of his life paralysed and unable to walk.

"They told us he'd be a quadriplegic, they told us he'd have brain damage, they told us to turn the machine off, twice actually," Wanda said.

"I knew that if his spinal cord wasn't severed there would be hope."

Remarkably, Seth slowly began to move, first his shoulder, then his fingers, and then his toes until eventually he was up and walking again.

Even doctors are stunned by Seth's medical defiance, and say they cannot believe how far he has come.

Seth was just six-years-old when he was involved in a horror crash at Swan Hill. Photo: 7News

The Royal Children's Hospital's Orthopedic surgeon Dr Ian Torode said: "The sky is the limit really, he will be functioning perfectly well in the community - so it's a pretty bright future."

"He's a miracle boy," Wanda added.

While Seth was in hospital the Starlight Children's Foundation sent him to Queensland granting his wish to get slimed at Dreamworld theme park.

Now the newly mobile nine-year-old is planning a two-kilometre walkathon to raise money for the foundation.

He's confident he can go the distance.

To donate to Seth’s Walk for Starlight, send a cheque to:

Starlight Children's Foundation / Seth’s Walk for Starlight