Swift medical attention has given cricketer Phil Hughes the best possible chance for a positive outcome, a top emergency doctor says.

The CPR and excellent hospital care given to cricketer Phillip Hughes has given him the best possible chance of recovery, a leading emergency doctor says.

Hughes, 25, is in an induced coma and fighting for his life following emergency surgery to reduce pressure on his brain after he was struck on the head by a bouncer at the SCG on Tuesday.

The president of the Australasian College of Emergency Medicine, Anthony Cross, said Hughes' treatment would involve doing further scans and monitoring for swelling in the brain.

Dr Cross, who has not been involved in treating Hughes, said a ball travelling at speeds of around 145km/h that impacts the cerebellum or "little brain" region at the back of the head could inflict incredible damage.

"He sustained the blow and then a few seconds later collapsed.

"There would rapidly be some bleeding inside or around the brain, which leads to a build up of pressure in an important part of the brain which is responsible for his balance and wakefulness.

"When he had the operation on Tuesday they would have made sure there was no further bleeding and stopped it if that was the case.

"I suspect they may have taken part of the skull off to allow a bit of space, if there is swelling then it can swell without compressing structures inside the skull.

"And then I understand he's been sedated, put in an induced coma, and the idea there is to allow a bit of time to see what happens with swelling."

Dr Cross said Hughes was fortunate to be given CPR on the stretcher as he came off the field.

"People treating him did exactly the right thing - the first aid response that we teach people is that if a patient becomes unconscious and unresponsive we should start treatment with CPR immediately."

The long-term impacts on health and time-frame for recovery are difficult to predict with brain injuries, he said.

"There could be no real impact at all, to the possibility that he has a severe brain injury as a result of this.

"Given that this was witnessed and he had very good treatment immediately and was rushed to a hospital and received excellent care, he has the best possible chance of having the best possible outcome."

Brain Injury Australia spokesman Nick Rushworth said recovering from a brain injury is a marathon.

But that doesn't mean there's no hope for Hughes, he says.

"It could be that Phil is inside the bell curve and there could be some profound consequences," Mr Rushworth said.

"Or he could be an outlier, he could be playing cricket at some time in the nearest future."

AAP.