My sister's asked me to post and see whether anyone can explain an odd nervous twitch my 6yo niece has. When she's over-excited, she does this thing where she shakes, flaps her hands and grimaces. She's aware of it and conscious throughout - when my sister asked, she said 'she has to do it'.
Any clues about what it is, and whether we should ignore or try to do something about it?
p.s. my sister's a nurse - seems relevant somehow.