The good news, O'Shanick says, is that if a patient begins to recover, the rate of recovery seen in the months after injury is often rapid.
"Think about the injury as being your birth," he said. "If you look at the development from infancy as kind of a backdrop, the first part of recovery in that first six months is going to be meteoric."
In this phase, with any luck, the patient regains the ability to feed himself or herself, walk with assistance, and perform other basic tasks. Some gross motor skills and basic movements may also return.
To family members, the progress may be heartening, but this rapid rate of improvement, in most cases, does not last.
About six months after many traumatic brain injuries occur, patients begin to experience a slowdown in improvements.
Rehabilitation at this phase normally involves developing safety awareness and balance, cognitive rehabilitation to improve memory, and dealing with impulsivity and multitasking.
Patients may also be able to refine their motor skills, develop more sophisticated cognitive skills, articulate more effectively, and control their impulses.
However, constant care is still needed.
"When you take a look at recovery of function, you have to look at it case by case," Ashley said. "Approximately 5 [percent] to 20 percent of individuals who have sustained a mild TBI or concussion will have one or more symptoms that last a year or longer."
"These patients are entering a lifelong period of attention, concentration, memory, fatigue, cognitive and emotional disabilities."
After the first few years following injury, the improvement curve in most cases becomes completely flat; patients rarely improve past this point.
"What you see as problems at two years after injury are generally seen as permanent," O'Shanick said.
However, a few patients can recover from their injuries enough to continue their lives to a certain degree.
Abigail Baglione, a senior at NYU, was out with friends on the night of Sept. 20, 2000. It was a typical night on the town until the car they were riding in was broadsided by another vehicle.
Baglione, who was sitting in the front passenger-side seat, received the brunt of the impact.
The brain injury she sustained from the crash impaired her ability to think and learn.
"Awareness and realization takes a long time," she said. "It was really hard, and I went through periods of depression."
Yet, the damage to her brain was limited in severity. Perhaps most important, her sense of motivation, which many TBI patients lose after their injuries, was not affected.
"I really, really wanted to go back to school, so I made that happen," she said.
Her return to NYU was a challenge. Baglione was in her senior year when the accident occurred; finishing her final two semesters took two extra years.
Nonetheless, she graduated in May 2003, and is currently at NYU working toward her master's degree in social work.
She says she still suffers from fatigue and takes stimulants to stay awake and focus. She also says that she learns more slowly now, and that her organization skills are not as keen as they used to be.
But she realizes her condition could have been much worse.
"I am really lucky," she said.
Statistics suggest Baglione is fortunate, indeed.
"The vast majority of individuals who have had a traumatic brain injury, five to seven years post-injury, will not have returned to work," Ashley said.