Arizona congresswoman Gabrielle Giffords has left a Tucson hospital for a rehab centre in Texas, where she will begin the next phase of recovery from her gunshot wound to the head.

Giffords' husband Capt. Mark Kelly, who lives and works as an astronaut in Houston, says he's very optimistic that she's on the road to recovery.

"I imagine the next step here is she'll be walking, talking, and in two months, you'll see her walking through the front door of this building," Kelly said Thursday at the Tucson hospital where she was taken after the shooting.

"I'm extremely hopeful that Gabrielle is going to make a full recovery."

But others are warning it may be too early to hope that Giffords will return to the life she once knew.

While it can be exciting when a patient beats the odds and survives a gunshot wound like the one Giffords has, Dr. Mark Bayley, the medical director of the Neuro Rehabilitation Program at Toronto Rehab, says it's important to be realistic.

"We have good reason to be concerned that (Kelly's prediction) is overly ambitious, given the nature of her injury," he told CTV Friday morning.

Bayley estimates that only about one per cent of his patients recover in two months from an injury like the one Giffords has sustained.

That said, Bayley notes that every patient is different and the brain is amazing in its ability to recover.

"There is reason to be optimistic. We know that the brain has quite remarkable powers," he said.

"And that's part of why we in rehab programs get excited, because the brain can re-organize. The part that's injured can redistribute its responsibilities to other parts. So the area that's responsible for speech can pull in other areas of the brain to help recover. And it's really an exciting process."

Giffords' doctors at first surmised that the congresswoman had been shot in the back of the head, that the bullet travelled the length of her brain, and then exited out her forehead, over her eye.

But according to police, surveillance video from the Arizona grocery store where Giffords was speaking now suggests she was shot in the forehead from about half a metre away.

It's thought the bullet may have damaged her speech centres and perhaps her ability to see.

Bayley notes it's important to begin rehabilitation from a brain injury as soon as possible.

"We know from animal and human models that the earlier you get can get rehabilitation, the earlier you start doing those tasks and training, the better the outcome," he said.

Giffords will likely stay at the in-patient rehab hospital in Houston until she no longer needs 24-hour medical care, which will probably be two more months.

Then she will likely be transferred home, returning to the rehab facility for up to five hours a day for physical and other rehab therapies.

Bayley predicts Giffords will have a huge team helping her:

  • physiotherapists to help her walk and move again
  • occupational therapists to help her re-learn everyday tasks
  • speech therapists to help her re-learn to talk
  • psychologists and social workers to help her with her emotional needs
  • neurologists, nurses and pharmacists to attend to her medical needs

While the Texas rehab hospital will likely offer Giffords the best care possible, the facility's chief executive, Carl Josehart, sounded cautious when reporters asked him if he expected Giffords' to recover completely.

"Not everyone always gets 100 per cent restoration, but we help them to get to a new normal," he responded.

Bayley too suggested it will be difficult for Giffords to recover enough to return to her job quickly. Giffords was injured on the left side of her brain, where her speech centres would have been located, and it's unclear if she can see, speak, or communicate beyond hand squeezes.

"The left hemisphere is important for speech and that would of course be a critical function for a politician," he noted. "They've got to communicate, they've got to build relationships, they've got to read very detailed legislation. And I would foresee that would be a real challenge for her given what we know right now.

"We all want to maintain hope but I think it's important to be realistic."

With reports from the Associated Press