I think they call it Thoracic Outlet Syndrome mainly due to the whole thorax area being involved.{rib cage area front & back}
Some do get something called a T4 syndrome also.
http://www.ncbi.nlm.nih.gov/sites/en...t=AbstractPlus

It is confusing, some call it brachial plexus injury also.
The links in my other post can explain it much better.

It can be caused by whiplash or other types of car accidents, as well as many other causes, and be secondary to his c spine injury/symptoms.
And not many drs are knowledgeable about TOS.

But to help Oscar better, more info would be best.