He's still way too young for naughty step (although personally I'd never use that anyway, I prefer children to learn how to behave by working out the natural consequences, not to behave just to please others or for a gimmick
http://www.alfiekohn.org/parenting/supernanny. htm ).
It's very frustrating to have feelings you can't name let alone convey to others. Then to be ignored for having strong feelings (even if about something absurd to you) is going to confuse such a young child. They need comfort to be able to calm down, it's scientifically proven (see the Science of Parenting by Professor Margot Sunderland). By aiding them calming down while young will help them learn to control these emotions themselves later on. Withdrawing comfort can give mixed messages. Remember they don't know or have the understanding you do.
Also at 13 months they tend to have very little empathy for others yet and no idea their actions hurt.
The headbanging could be a need for comfort. Has anything changed recently? What about his diet, do you have much caffeine at all that could pass on to him? Does he have squash with sweeteners in etc?
http://www.askdrsears.com/html/6/T060400.asp
This book may really help see things from his point of view, then help you calm him down or avoid the stressful situations before they kick off!
http://www.socialbaby.com/shop/product.asp?P_I D=404
This might help too
http://www.pinky-mychild.com/index.php?option= com_content&view=article&id=35&Itemid=25