Answers:
Dystonia is a neuromuscular disorder that cause a soul muscles to spasm and contract. These contracted position may be held for long period. Giving the individual a twisted, uncomfotable and sometimes itchy posture.
While dystonia is a disorder onits own it is also a symptom of other Neuromuscular disorders.
As to the motive mostly it is Genetic. But they also come up with in that may be links near trauma and syndrome. Also as within other neuro disorders in attendance may be spontaneous occurances next to no certain exact. So really what it comes down to is unless you show clan history they merely dont know why!?
I hope this help!