Try to think of a panic attack as your brain being given too much information to process and not being able to sort it out so it can process it one piece at a time. The concussed brain has much less ability to sort out information and stimulations so it will tend to go into panic mode with lesser amounts of over-stimulation. Altering brain chemistry can make this even more of a problem.

It sounds to me as if you need to learn to live with a very sensitive brain, at least for the near future. This may be a long term issue.

Learning to let go of worries and such is extremely important with PCS. Maybe a therapist who understands PCS can help you learn some coping strategies. You may be able to get a referral from a Neuro Rehab clinic or hospital.

My best to you.