A SIMPLE squeeze of the hand revealed positive signs for Graham Polak's brain yesterday as doctors slowly woke him from an induced coma.

Like many patients before him, the Richmond defender showed medics at The Alfred hospital by responding to the request that he could be drawn out of a drug induced coma.

The manoeuvre is one of several tests used to ensure a patient with a head injury is fit to be woken and possibly taken off life support as doctors reduce the sedating drugs being fed into the blood stream.

"First of all, the patient starts to localise; they try to pull the breathing tube out of their mouth or anything else that annoys them," said neurosurgeon Richard Bittar.

"They might also open their eyes to pain. As the sedation gets lighter, they start to move around on their own a bit more or they'll start to open their eyes as you talk to them.

"The final step is for them to obey commands like 'close your eyes', 'squeeze my hand' or 'wiggle your toes'."

Depending on the severity of the head injury, the progressive signs of brain activity can be demonstrated in as little as an hour or over the course of weeks. The lucky ones will go on to talk.

"Initially they might just make grunting noises, but then they'll say some words, which usually won't make sense. They might even start to talk, but they will usually be confused and disoriented," Dr Bittar said.

"Hopefully they get to the point where they have a conversation and talk about what's happened to them, the day of the week and all those sorts of things."

For many patients who have suffered head injuries, an induced coma is used to protect their airways, control or reduce swelling of the brain and immobilise their bodies to assess other damage.

"In these patients, the last thing you want is swelling in the brain, because the brain has nowhere to go," Dr Bittar said.

"It is effectively in a box, which is the skull, so if it swells it gets squashed.

"That reduces the amount of blood flow substantially, and that can result in stroke or death."

While Polak exhibited signs of recovery yesterday, the extent of his injuries could remain unclear for months.

"It can be weeks or months before you know the effect of the brain injury on someone's personality, their intelligence, their speech, their fine motor skills, all of those things," Dr Bittar said.

"It takes time. In the early stages, we're about trying to make sure they survive and survive well — but that's the difficult part in the long term."