Anxiety is too probably my only lasting symptom from the concussion. Although having said that anxiety itself has a lot of symptoms, nausea, headaches, fatigue, etc can all be bought on my anxiety.

Like Mark says, its often really hard to differentiate what is an anxiety response and what is a concussion response. If I analyzed my own behaviour like you I had a tenancy for precursors to full blown anxiety, but it didn't hit me like it has 'post the event'. I also agree the concussion, or at least the stress from a possible concussion can be the event which creates the build up of anxiety.