I know someone with half a brain. It is the result of a hemispherectomy, usually done for intractable epilepsy. My friend had it done for just such a reason when he was in elementary school. The first hemispherectomy was done by Dr Ben Carson about 25 years ago. The other hemisphere can take over many of the functions.

The problem with good PCS and mTBI diagnostics is based on money. There is not a financial advantage to a good diagnosis. The pharmaceutical companies cannot sell drugs for brain injuries since none exist. There is a very good diagnostic tool called QEEG. It uses a computer to sample EEG brain wave data with millisecond resolution. Most EEGs are visually interpreted at a macro scale. Problem with QEEG is an idiot neurologist wrote and scathing article against QEEG back in 1997 that has been used by insurance companies to refute the validity of QEEG diagnostics ever since. That article has been soundly refuted by many peer reviewed articles but it is still held as valid in many circles.

The Veterans Administration has done some more research but the validity of the QEEG has not spread. The vast majority of Neuro-psychologists tend to discredit QEEG. They like to have the final word with their neuropsychological assessments.

There are other tests that are valid too, such a fMRI, functional MRI, and Diffusion Tensored Imaging, a MRI derivative. These are expensive and rare, usually just in research facilities presently. fMRI is quickly becoming more common.

In my research and experience, the QEEG has the most value in diagnostics. There are databases of over 10,000 subjects to compare results to. I have had it done 4 times. The neurologist reading the results could tell me what I was experiencing without knowing my symptoms. That is a very objective test result. Even his QEEG tech could tell me what was happening in my brain. BTW. The QEEG tech had previously had a double lobe-ectomy. He had an invasive tumor removed with two lobes involved. He went on to get a bachelor's and master's degree with only two thirds of his brain left.

The important part of lobe-ectomies is that they no longer get in the way of the rest of the brain by sending out erroneous signals. The healthy lobes can now rewire to take over for the missing parts.

In PCS and many mTBI's, the damage is more global, effecting most areas of the brain. This weakness prevents most or all lobes from functioning at a full level. When the damage effects the corpus colosum, it is like the telephone company having a flood at the main switching station. The signals may come into the switch fine but cannot get past the switch properly to go on to the other areas. This is a common PCS issue.