Athetosis

Athetosis is a nonprogressive disorder arising from damage to the basal ganglia. It is characterised by involuntary athetoid movements such as a continuous stream of slow, sinuous, writhing movements, typically of the hands and feet. Postural reflex impairments and dysarthria can also accompany the condition but sensation and intelligence are generally unaffected

Causes
It is said to be caused by damage to the corpus striatum of the brain, and can also be caused by a lesion of the motor thalamus.

Athetosis is to be distinguished from pseudoathetosis, which is abnormal writhing movement, usually of the fingers, occurring when the eyes are closed, caused by a failure of joint position sense (proprioception), for example in peripheral neuropathy.