Chorea (Greek for "dance") refers to irregular, rapid, flowing, non-stereotyped and random involuntary movements that often possess a writhing quality, referred to as choreoathetosis. When mild, it may be difficult to differentiate from restlessness. The movements can be strikingly asymmetric, as in hemichorea, or generalized. When chorea is proximal and of large amplitude, it is called ballism. Chorea is worsened by stress and anxiety and subsides during sleep. Movements can interfere with the completion of many daily activities, making fastening a button a substantial effort. Chorea often is incorporated into a purposeful activity in an attempt to disguise it. Motor impersistence is a common associated feature, demonstrated by varying intensity of grip strength (milkmaid's grasp) or by an inability to sustain eye closure or tongue protrusion.