Dystonia causes involuntary repetitive twisting and sustained muscle contractions. These result in abnormal involuntary movements and postures. The symptoms usually begin in one body region such as the neck, face, an arm, and may spread with time to other body regions. When dystonia affects children, it often starts in a leg before spreading to other limbs and trunk. In adults, dystonia tends to remained localized to a body region and frequently affects the upper body.