Spinning, tail chasing and  sudden aggression are all different forms of the same inherited behavioural disease. The affected dogs tend to chase their tail or spin which sometimes can end in self mutilation. This condition is considered, at the moment, to be polygenic  which means that it's occurrence is determined by more then one gene. This episodes are considered to be a form of epileptic seizures and many dogs can improve once they start anti-epileptic medication. 

   A very good website with a large amount of information from specialists but also personal experience of owners of spinners can be found here.