Effects of age on motor excitability measures from children and adolescents with Tourette syndrome

Abstract

Tourette syndrome (TS) is a neurological disorder characterised by vocal and motor tics. It is associated with cortical-striatal-thalamic-cortical circuit [CSTC] dysfunction and hyper-excitability of cortical motor regions. TS follows a developmental time course, in which tics often become increasingly more controlled during adolescence. Importantly, however, a substantial minority of patients continue to have debilitating tics into adulthood. This indicates that there may be important differences between adult TS patients and children and adolescents with the disorder. We use TMS to examine cortical motor excitability in a sample of children, adolescents and young adults with TS. We demonstrate that, in contrast to studies of adult patients, resting motor threshold and the variability of MEP responses are increased in children with TS, while the gain of motor excitability in reduced. Importantly, we demonstrate that these differences normalise with age over adolescence. We conclude that these effects are likely due to a developmental delay in the maturation of key brain networks in TS, consistent with recent brain imaging studies of structural and functional brain connectivity. Importantly, these findings suggest that the alterations in brain network structure and function associated with TS may be quite different in children and adult patients with the condition.

Tourette syndrome research highlights from 2016

“…In contrast to findings from previous studies in older patients, resting motor threshold and variability of motor evoked potential responses in 17 TS subjects, age 12–22, were increased versus controls, while the gain of motor excitability was reduced 42 . The authors suggest that these findings may relate to delayed maturation of the cortical-cortical and corticospinal motor networks in TS.…”

Less-Affected Hand Function in Children With Hemiparetic Unilateral Cerebral Palsy: A Comparison Study With Typically Developing Peers

“…Others have reported significant motor threshold differences between diagnostic groups of children with Tourette’s Syndrome 43 and typical development and in children born early preterm birth (≤32 weeks gestational age) as compared to late preterm (33–36 weeks’ gestation age) and term-born (37–41 weeks gestational age) groups 44 . Pitcher et al (2012) proposed that the lower cortical excitability as reflected by a higher resting motor threshold in children with early preterm birth may reflect weaker connectivity between the primary and secondary motor areas.…”

Clinical Features That Evoke the Concept of Disinhibition in Tourette Syndrome

“…Some general measures of motor cortical excitability, e.g. resting and active motor thresholds, are not different in TS patients from those in healthy controls (84), whereas other measures such as the recruitment of motor-evoked potentials (input/output curves) suggest reduced baseline excitability (84,88,99). Similarly, some magnetoencephalographic cortical event-related studies also revealed patterns of enhanced inhibitory function (100,101).…”