Characteristic of tics we may mention their being conscious before and after but not during their execution, their being disordered functional acts, their impetuous, irresistible demand for execution, the antecedent desire, and the subsequent satisfaction.
The etiology of tics, as laid down by Meige and Feindel, may be summed up by stating that they occur most frequently in young subjects, less frequently in savages and animals than in the civilized, there is a psychic predisposition based on heredity (of a similar or dissimilar neuropathy or psychopathy) upon which Charcot laid great stress, imitation (especially in the young) plays a role, as also brain fatigue (emotion, mental upset and worry) and indolence, with the frequent exciting cause of an external or internal stimulus or an idea, which is the explanation of the origin, source, situation and form of the tic or tics present in any particular case.
Scattered references to emotional shock acting as a possible exciting cause of tics, as at times of obsessions, can be found in the literature. Dupre[2] has made such reference. Meige and. Feindel[3] themselves make the statement that "Fear may elicit a movement of defense, to persist as a tic after the exciting cause has vanished." They also state that "in ticquers the impulse to seek a sensation is common and also to repeat to excess a functional act."
[2] Soc. de Neur. de Paris, April 18, 1901, quoted by Meige and Feindel, page 54, of the English translation (reference 1).
[3] Loc. cit., p. 62.
Bresler[4] has called attention to the fact that the movements are in the nature of defensive and protective movements of expression and mimicry and originally in reaction to some external irritant or as the result of some idea, and he proposed the name "mimische Krampfneurose" for them. This is somewhat allied to Breuer and Freud's theory of hysteria.
[4] Quoted by Meige and Feindel, Loc. cit., p. 267.
The object of tic is some imaginary end, the influence of the will always being present in the beginning, although later it may be absent. Tics are of cortical origin, being coordinated and synergic, clonic or at times tonic[*] muscular movements, physiologically and not anatomically grouped, premeditated, purposive, of abnormal intensity, apparently causeless and inopportune.
[*] Cruchet objects to calling these tonic reactions tics.
Insufficiency of inhibition is the cause of the beginning and of the persistence of bad habits and of tics.