absolutely! CST is gentle and everything has been cleared the client should benefit greatly.
I have worked with many individuals post head trauma over the many years and with great results!
I think it should be fine. You may want to start energetically or use very light touch. It should be a perfect modality, as long as there isn't too much swelling. See if you can get A Body Talker to do a session on them to make sure that the anatomy of the brain is communicating and synced up properly.