[Functional cramps or functional dystonias in writers and musicians].

The clinical evaluation in the "dystonies of function" or "impaired dexterity" reveals certain physical anomalies which either appear spontaneously or are triggered by specific tests: abnormal postures involving the trunck, head, and upper limb. During the professional gesture the physiological "pulley effect" on flexor tendons is accompanied with an interference effect produced by the displacement of the segments; this, adds up to an unbalance of the digital kinetic chain, building a locked functional system. The antagonist muscles begin to supply the deficiency of the agonist muscles. In addition, patients with a characteristic psychological ground suffer a more acute "disorganization" or a performing career.