Dystonia

Abstract

Dystonia is a syndrome of sustained muscle contractions that produce involuntary twisting and repetitive movements and abnormal postures of the trunk, neck, face, and extremities. Somewhat confusingly, the term “dystonia” has been used to designate a specific type of abnormal movement or posture, a syndrome that occurs secondary to a number of underlying neurologic disorders, and a primary disorder known as “idiopathic torsion dystonia.” Dystonic movements can be either slow or rapid and are usually more stereotyped and patterned than movements in chorea (random and unpredictable), myoclonus (brief and shocklike), and tremor (rhythmical and not associated with alterations in posture). Dystonia is characterized by failure of normal reciprocal inhibition, which causes co-contraction of agonist and antagonist muscles accompanied by excessive contraction of other regional muscles. This chapter is limited to conditions characterized by continuous rather than intermittent dystonia and therefore does not include discussion of the paroxysmal dystonias. Psychogenic dystonia is discussed in Chapter 35 together with other functional movement disorders.