Athetosis describes repetitive involuntary, slow, sinuous, writhing movements, which are especially severe in the hands. There are also elements of postural disturbance.
Athetotic movements are around the axis of the limb, as distinct from choreiform movements, which are at right angles to the axis. As with chorea, the lips, jaw and tongue may also be involved; this leads to facial grimaces and dysarthria.
These movements are usually congenital but may result from focal lesions to the corpus striatum, particularly the outer part of the putamen.