Tourette syndrome (TS) is a neuropsychiatric disorder characterised by motor and phonic tics. Deficient motor inhibition underlying tics is one of the main hypotheses in its pathophysiology. Therefore the question arises whether this supposed deficient motor inhibition affects also voluntary movements. The severity of tics waxes and wanes over time. Patients often report that stress and teasing by others worsen tics, whereas focused activity such as reading or voluntary motor activities such as playing basketball reduces the occurrence of tics
TS is often accompanied by comorbidities such as obsessive-compulsive disorder (OCD), depression and attention-deficit-hyperactivity disorder (ADHD)
[5, 6]. The cortico-striato-thalamo-cortical circuit plays an important role in the pathophysiology of TS. Tics respond to treatment with D2-receptor blocking agents with high striatal affinity
[7–9]. Therefore, the neuroanatomy of tics has received particular attention in neuroimaging research on Tourette syndrome
[10, 11], highlighting a network of frontal areas, basal ganglia, insula and cerebellum, compatible with the notion that TS is the result of a failure in network maturation, particularly of the fronto-striatal-thalamic-cortical loop
[12–14]. Structural changes have been described in Tourette patients, such as grey matter reduction in orbitofrontal, anterior cingulate and ventrolateral prefrontal cortices
. Alterations in amygdala structure and its functional connectivity are also reported
Recent imaging studies in TS report an involvement of the corticospinal tract and of the underlying white matter under the supplementary motor area, the pre- and postcentral gyrus and the ventral-posterolateral nucleus of the right thalamus
[19, 20]. There are reports of reduced volumes of the caudate nucleus across the life span and thinning of sensorimotor cortices in proportion to tic severity in children suffering from Tourette syndrome
. Hypertrophy of limbic and prefrontal cortices and a smaller corpus callosum are associated with less pronounced tics in children with TS
[22, 23]. For the different clinical phenotypes of Tourette syndrome (e.g. simple tics, simple and complex tics, tics and OCD) Worbe and colleagues reported cortical thinning in primary motor regions in patients with simple tics. In patients suffering from simple and complex tics the cortical thinning was spread to larger premotor, prefrontal and parietal regions, and a trend for reduced cortical thickness in the anterior cingulated cortex and hippocampal morphology was reported in patients with comorbid obsessive-compulsive disorder
Given the feature of tics as motor symptoms the question arises whether fine motor skills are affected in Tourette syndrome. There is a limited number of studies in children and adults to this end. In 1990 Bornstein published the results of a comprehensive neuropsychological test battery for 100 children and adolescents with Tourette syndrome
. T-values of the finger tapping task for the dominant and non-dominant hand were within normal limits. Performance for the grooved pegboard was normal for the dominant hand and impaired for the non-dominant hand (t=34.6). In a recent behavioural study in 11 adult Tourette patients Jonas and colleagues reported behavioural results on simple finger movements in adult Tourette patients with focus on echophenomena
. They described no significant difference in the reaction time of simple motor tasks between patients and a healthy controls group. However, when confronted with the task of copying a single finger movement following an incongruent biological stimulus Tourette patients showed a marked decline in performance with increased reaction times.
The clear affection of primary motor structures in recent neuroimaging studies would suggest that fine motor skills are impaired in Tourette patients
[10, 11, 18, 19, 26–28]. On the other hand, clinical observations show that patients are able to suppress their tics at a certain degree of focused attention and also at some movements accomplishment, e.g. tics are often reported to be reduced in sports. Tourette patients are found among top athletes, professional piano players and neurosurgeons.
For the investigation of fine motor skills we conducted a motor performance test battery [Motorische Leistungsserie (MLS), Wiener Testsystem] in an adult Tourette sample. We aimed to address the following questions by our study:
a) Are fine motor skills in Tourette patients altered as possibly indicated by neuroimaging studies showing changes in the motor system?
b) What differences in task performance can be observed between TS patients and healthy controls?