It's could be a gunshot wound or a car accident. Serious damage to the brain and at least an initial loss of function.
"The brain is a living organism. It changes and some other parts of the brain can take over functions that were lost. And even the other side of the brain can take functions lost on one side. So there is capacity for recovery," Nichols says.
Freeman neurosurgeon Ellen Nichols says each patient heals differently - but she's seen some amazing results in recovering brain connections.
"They've just got to find a way to get to the right place. And sometimes they find their way to the wrong place and then you have to retrain your body to respond to that stimulation in a different way," she says.
Nichols says younger patients usually have better recovery. Other factors include the patient's overall medical condition, the type of brain injury and how severe it is.
"We see some patients with fairly significant head injuries that do make essentially a complete recovery, so that maybe other people can't tell that there's been any problem at all that the patient themself is the only one who knows if they're struggling a lil bit with memory or some other function but many cases, there's damage that's not recoverable. And those patients then learn to function with a different brain and different capacities," Nichols says.