Stone and Jankovic have noted the occurrence of blepharospasm, torticollis, and other dystonic fragments in a small number of patients. Isometric contractions of isolated muscle groups (tonic tics) may also occur. As in other tic disorders, there is a premonitory sensation of tightness, discomfort or paresthesia, or a psychic sensation or urge that is relieved by the movement. A fair proportion stutters or displays a mild dysfluency of speech. So-called soft neurologic signs are noted in half of the patients. Feinberg and associates have described four patients with arrhythmic myoclonus and vocalization, but it is not clear whether these symptoms represent an unusual variant of the disease or a new syndrome. A degree of cyclicality of symptoms has been noted by several authors; tics tend to happen in groups over minutes or hours and they are clustered over weeks and months. This gives the appearance of a waxing and waning process.
The course of the illness is unpredictable. In half of adolescents the tics subside spontaneously by early adulthood and those that persist become milder with time. Others undergo long remissions only to have tics recur, but in other patients the motor disorder persists throughout life. This variability emphasizes the difficulty in separating transient habit spasms from the Gilles de la Tourette chronic multiple tic syndrome. Isolated and mild but lifelong motor tics probably represent a variant of Tourette syndrome insofar as they display the same predominantly male heredofamilial pattern and similar responses to medication.
An attention-deficit hyperactivity disorder, obsessive-compulsive traits, or both are said to be evident at some time in the course of the illness, and these interfere with progress in school to a greater degree than do the tics. Poor control of temper, impulsiveness, self-injurious behavior, and certain sociopathic traits are seen in a few but by no means all affected children. Evidence of cognitive impairment by psychometric tests was found in 40 to 60 percent of patients in the series reported by Shapiro and colleagues, but intelligence did not deteriorate. Nonspecific abnormalities of the EEG have occurred in more than half of the patients but are not consistent enough to be considered a feature of the disease.
In one-third of the cases reported by Shapiro and colleagues, isolated tics were observed in other members of the family. Several other studies have reported a familial clustering of cases in which the pattern of transmission appears to be autosomal dominant with incomplete penetrance (Pauls and Leckman) but this has been disputed and several predisposing genes have been found. In any biologic explanation, the marked predominance of males must be accounted for. At the moment, Tourette syndrome cannot be attributed to a single genetic locus. Nonetheless, support for a primary genetic nature of Tourette syndrome derives from twin studies, which have revealed higher concordance rates in monozygotic twin pairs than in dizygotic pairs. An ethnic propensity has been reported in Ashkenazi Jews but this has not been borne out in other large series (Lees et al).