The direct cause and pathophysiological basis of<unk>  is still unknown and can occur in children and adults of perfect or non-perfect health. Rare cases of adult<unk>  have developed due to head trauma, stress, and herpes encephalitis. Familial cases have been reported suggesting there may be some genetic aspect to the<unk> ; however, to date, this explanation has not been directly tested. As familial incidence rate is still relatively low, it is believed that behavioral aspects may play a larger role in<unk>  than family history and genetics. Many sufferers report no family history of the<unk> . Another theory suggests that<unk>  is a learned, self-stimulating behavior to alleviate tension and induce relaxation, similar to tic<unk> s. An alternative theory suggests that the<unk><unk> s help develop the vestibular system in young children, which can partially explain the high prevalence of<unk>  in infants. It has been seen that children who have underdeveloped vestibular systems benefit from performing<unk> -like<unk> s which stimulate the vestibular system .
Rhythmic movement disorder
Essential tremor
Dopamine-responsive dystonia
Benign fasciculation syndrome
Torsion dystonia
Paroxysmal exercise-induced dystonia
Focal dystonia
Stiff-person syndrome