My son is a teacher (27 years) old...who has been suffering from Post Traumatic Concussion for more than 3 months. He has returned to teaching in November, but still suffers daily from headaches, sometimes dizziness, and certainly drained & tired by the end of the day. We have paid for absolute full medical testing to be sure there are no other underlying causes, and so far, nothing has come up. He also had a CTScan which also came up OK. However, about 8 days ago he developed an unvoluntary head "jerking". His head literally gets pulled backwards and he has no control over the movement. It has him extremely concerned, and there is nothing in anything we have read that relates this to a symptom of the concussion. Is this normal??? Should we be concerned?? What type of medical help (if any) should we seek? Thank you in advance for any information you can provide!!!