Hopes that Michael Schumacher can emerge quickly from his coma like "in the movies" are misplaced, a brain expert has warned.

The road to a recovery of any kind is likely to be a long one for the Formula 1 legend, said Luke Gregg of the brain injury charity Headway. Emerging from a coma does not mean the injuries are gone and in fact they might "last a lifetime," he cautioned.

Schumacher, 45, lay in a medically induced coma for five weeks after banging his head while skiing in the French Alps. It was a longer spell than the usual two weeks and has been interpreted as a sign of how serious the German's injuries are.

Efforts to lift him from the coma began last week when sedation was eased by medical staff at the hospital in Grenoble treating Schumacher. Early reports indicated good progress.

But Gregg said: "Waking from a coma is not like how it is portrayed in the movies. It can be a very gradual process that can take several days or weeks.

"For the family, the initial fear about whether or not the individual will survive is replaced by fear of what the future will hold and what level of recovery their loved one will make.

"Put simply, the effects of brain injury can be devastating and last a lifetime. It can change every aspect of you: walking, talking, thinking and feeling. It can change personalities as well as capabilities."

Announcing the start of the bid to end Schumacher's coma last week, his family said in a statement: "Michael's sedation is being reduced in order to allow the start of the waking-up process which may take a long time."

The former Ferrari and Mercedes driver's spokeswoman Sabine Kehm said he was in a "stable" condition.

"I also repeat that Michael's family is very happy and confident with the work of the team of doctors treating Michael, and they trust them completely," she said.