I am not sure if this is related to what you guys are experiencing, but my daughter's left arm will twitch/temor when she gets really stressed or her system goes into overload. Sometimes it's just her thumb and index finger, sometimes her hand and then her whole arm. It just kind of depends. It's better now than it was previously. The interesting thing was this didn't start right after her concussion, but maybe 5 weeks into it - when she freaked herself out about going back to school. She also started stuttering at that time. The stuttering has since resolved and twitch/temor is much better.