Symptoms Not Characteristics

" I need a lot more rest than I used to. I’m not being lazy. I get physical fatigue as well as a “brain fatigue.” It is very difficult and tiring for my brain to think, process, and organize. Fatigue makes it even harder to think.
My stamina fluctuates, even though I may look good or “all better” on the outside."  http://braininjuryknow.blogspot.com/2015/08/i-need.html

This sounds like rewirlng. It also sounds like a lot of brain injuries.

The brain uses energy. "It is well established that the brain uses more energy than any other human organ, accounting for up to 20 percent of the body's total haul." http://www.scientificamerican.com/article/why-does-the-brain-need-s/

Take away that energy, or put it somewhere else, of course one

will get tired. Fatigue can be a symptom of brain loss or rewiring. It is not safe to assume it is due only to brain loss.

"My stamina fluctuates" is my Socially Awkward Penguin's comment. (He really is called "The Socially Awkward Penguin".)

As the skill is repeatedly performed, the neuropathway gets stronger. "In order for the brain to rewire an activity, the activity must be done repeatedly. Norman Doidge gives a description of this when he likens it to snow skiing, but uses it to explain a bad habit. "Plasticity is like snow on a hill in winter. If we want to ski down the hill we can take many different paths because the snow is so pliable and plastic. But being human we tend to favour one path and pretty soon we´ve developed a grooved track, which ultimately becomes a rut that is hard to get out of." http://thoughtfulveg.blogspot.com/2013/03/groove-me.html  This process of rewiring can take a long time. This process can also be called neuroplasticity.

It can be completed when this new neuropathway is used. The body has to be trained to use it. 

This video shows two neuropathways.The top one is the old damaged way. The bottom is the new  one that works. On days you can do your task, you are using the new neuropathway, or bottom. When you can't, it's the old.
 

These two "characteristics" of brain injury (fatigue and doing/not doing ability) can be "symptoms" of rewiring. This process can take a very long time. It can take years, and a lucky survivor of brain injury won't take as long. "Something" is going on and it should be tracked. Self-report in the form of a yes/no question on a social security form is not enough. (Obviously, if I am still vegetative.)

"So, come up to the lab,/ and see what's on the slab!/ I see you shiver with antici... [3-second long pause] ...pation./ But maybe the rain/ isn't really to blame,/ so I'll remove the cause.../ [chuckles] but not the symptom." The Rocky Horror Picture Show