Involuntary arm movements my arm moves and hits on the head continuously?

Arm jerking. Involuntary arm jerking may represent either seizure or motor tics, in case of seizure if the arm jerking is sudden and vigorus with preserving of awareness, it can be a myoclonic seizure, if the movement is rhythmic in one side and unable to control it but can feel it, so it can be a simple partial seizure, then eeg can help in the diagnosis. The other possibility is motor tic with normal eeg.