Recovering from a bullet wound to the head isn't like recovering from a broken arm, a heart attack or even cancer.
There is no path to follow, no clear sense of what recovery looks like.
Just as every brain is different, every brain injury is different. Giving a prognosis, doctors say, is little more than making a guess. U.S. Rep. Gabrielle Giffords - shot clean through the left side of her head on Jan. 8 - could be left with little lasting damage or significant, lifelong injuries, or anywhere in between, doctors say.
But it's likely the effects of the bullet will be with her in some way the rest of her life.
"Not everyone always gets 100 percent restoration," said Carl Josehart, chief executive of the rehab hospital that will be Giffords' home for the next month or two. "But we help them to get to a new normal."
Most recovery from the type of brain injury Giffords suffered typically occurs within the first year or two. Speech recovery could take months - and still could show improvement after a year, said Dr. G. Michael Lemole Jr., chief of neurosurgery at the University of Arizona College of Medicine and Tucson's University Medical Center.
Lemole is one of the two neurosurgeons who operated on Giffords after she was shot Jan. 8 in a rampage at a northwest-side supermarket that left six people dead and wounded 13, including Giffords. The Democratic congresswoman is the only one of those injured who remains hospitalized.
In the days after the shooting, survival was the goal. Now that it's certain Giffords, 40, will survive her injury, rehabilitation is the next step.
She was transferred from UMC to Houston on Friday. She's already begun therapy in the intensive-care unit at TIRR Memorial Hermann rehabilitation hospital, and as soon as she's well enough she'll be moved to the hospital's rehabilitation unit.
While doctors have refused to predict what Giffords' future will look like, they've said her progress so far has been remarkable. Doctors in Houston said she's in the top 5 percent of what they'd expect from a patient with a recent gunshot wound to the head.
Giffords was shot at close range. The bullet went in through the front of her head, just above her left eye, and exited through the back, doctors say.
Giffords will stay at Memorial Hermann until she no longer needs 24-hour medical care - the average is one to two months. Then she can get up to five hours a day of physical and other rehab therapies on an outpatient basis, said Carol Josehart, chief executive of the rehab hospital.
"It's hard to speculate on the trajectory or course that any one patient will have," Josehart said.
Sometimes, areas of the brain that seem damaged can recover, said Mark Sherer, a neuropsychologist at the rehab center.
"Some of the tissue is temporarily dysfunctional, so the patient appears very impaired very early on after the injury," but may not be permanently damaged, he said.
Each injury is different. Each patient is different. Here are two of their stories:
Cesar Peña was playing on a swing in his grandmother's south-side backyard, when a bullet fired in a neighboring yard tore into his forehead.
He was 8.
"The doctors didn't give me a lot of hope. He wasn't supposed to make it 24 hours," said his mother, Lizett Peña.
Now 10, the Drexel Elementary School student still has a half-inch scar running across the right side of his head. The scar is from the surgery he had at Tucson's University Medical Center after the July 14, 2008, shooting to remove a portion of his right skull to allow for brain swelling.
His hair hasn't grown into the scar yet, but he hopes it will.
Cesar wore a helmet for a little over a year until the skull portion was replaced. He still has limited movement on the left side of his body.
He can't open and close his left hand, or run very well. He wears a brace on his left leg and holds his left arm close to his body.
His mother says the injury has affected her son's mood - sometimes he gets sad easily, she said. But she said Cesar is also more patient than he used to be.
After he was shot, Cesar spent three weeks in UMC and then nearly two months in therapy at St. Joseph's Hospital in Phoenix. He also missed a year of school, which is why he's now in fourth grade instead of fifth. But his mother says his intellectual ability has not been affected by the injury and he does well in school.
"He's pretty smart," she said.
Cesar, a soft-spoken boy who likes to play outside with his younger brother, Andres, is optimistic about his continued recovery.
Indeed, doctors say children are more likely than adults to have a full recovery from traumatic brain injuries.
On Wednesday, Cesar received an award for having perfect attendance at school, where his favorite subject is science and he says other kids are nice and understanding about his injury.
He wants to be a firefighter for the Tucson Fire Department when he grows up.
"It took me like a month to talk. I couldn't walk a lot right away. My mom had to hold my hand," he said. "I still can't play my video games right."
In 2009, a jury convicted Jonathan "Jessie" Muniz, who was 18 at the time of the shooting, of aggravated assault and endangerment for firing the gun that hit Cesar. He was sentenced to 11 1/2 years in prison. Muniz, who lived a couple of houses away, had fired the shot that hit Cesar while showing his rifle to two friends. He'd apparently been aiming at a chair about 70 feet from where he stood. Cesar stood 100 feet beyond the chair.
"My brother went on the swing first and he told me it was my turn," Cesar said. "I don't know how, but the bullet got me and I fell back."
The boy's grandmother thought he'd fallen off the swing.
"I don't remember, but when I was in the ambulance the paramedics told her I'd been shot," Cesar said.
"He could have been dead," Andres said.
Unlike Giffords, the bullet that tore into Cesar's brain did not exit out the back. It's still there.
"At least her bullet left her head," Cesar said. "She'll get better. Then we'll be like buddies."
On his day off Wednesday, 45-year-old John Sabia drove 70 miles from his home in Willcox to Tucson to visit U.S. Rep. Gabrielle Giffords' office.
"I told them if she ever needs to talk to someone, I'm here. I've been there," he said.
He wanted to offer his support to the congresswoman, and also to give her inspiration, as Sabia survived being shot execution-style in the back of the head during a murder-suicide.
A bullet ripped through the left side of his brain Nov. 9, 2003, and fragmented. It remains lodged near the left front of his skull, as doctors determined leaving it there would be less risky than removing it.
Sabia was shot by his girlfriend's estranged husband, Michael Breaux. Breaux also killed Debra Breaux, their two children and himself.
The victims lay in the Breaux house overnight before anyone found them.
Sabia was hospitalized for 11 days at University Medical Center after the shooting, then for two weeks at the Southern Arizona Veterans Affairs Medical Center, followed by nine months in long-term rehabilitation at the Defense and Veterans Brain Injury Center in Palo Alto, Calif.
His mother, Irene Bendon, said she's been thinking about Giffords' parents.
"I just know that I was in such shock at the time when John was shot. I really didn't know what was going on," Bendon said. Giffords is "making a lot faster progress than John did. But he's pretty much a miracle man himself."
Sabia did not speak right away - it was two weeks before he uttered any words. His first movements were to squeeze the hands of friends and family.
He lost a lot of movement on his right side and walks with a cane. He is able to drive and write, and his vision was not affected. He speaks clearly, though there are often long pauses between words.
Now working part time with a company that specializes in employing people with disabilities, Sabia is doing maintenance work.
A 6-foot-2 former Marine embassy guard, Sabia had been stationed in Iceland, Russia and Italy, and also worked as a doorman and guard at the Westin La Paloma Resort in Tucson before the shooting. He also holds a degree in management information systems from the University of Phoenix that he earned in 2001, but he says he won't ever work in that field because of his injury.
"Basically my speech is a lasting effect. I choose words very carefully," he said. "Most of my improvements were in the first year. Little by little, day by day, I made leaps and bounds. I still make improvements. I am now able to walk unaided on uneven ground across the yard."
Sabia had a seizure close to the anniversary of the shooting in 2004 and is now on anti-seizure medications. He also thinks about the shooting constantly, he said.
"I know what she's going through," Sabia said of Giffords. "She is just doing amazingly well. Her bullet passed right through her head and they got to her right away. Those are the big differences between us. They didn't find me for 11 hours."
Traumatic brain injury
This refers to sudden damage to the brain caused by an outside force to the head, such as a car crash, a bullet or any blow to the skull. Such injuries can affect a person's ability to concentrate and remember, as well as cause problems with balance and coordination. Many survivors are severely disabled. Traumatic brain injury causes about 50,000 deaths and 80,000 new cases of long-term disability in the U.S. each year. Tucson's University Medical Center Trauma Center treats about 500 patients with moderate to severe traumatic brain injury each year.
The U.S. Surgeon General's Office has information about traumatic brain injuries at www.traumaticbraininjuryatoz.org/Home.aspx
The Associated Press contributed to this report.