Tic distribution and inhibitory processes in the sensorimotor circuit during adolescence: a cross-sectional TMS study

Deficient inhibitory processes within the sensorimotor circuit, reflected by a shortened cortical silent period (CSP), have previously been described in both children and adults with tic disorders (TD) using transcranial magnetic stimulation (TMS). In contrast to adults, tic distribution (presence or absence of distal tics) did not affect CSP duration in children. The aim of this developmental TMS study was to clarify this striking difference. 127 children with TD were stratified into three age-groups (8-11.5, 11.5-15, 15-19 years) with and without distal tics. CSP was recorded from the abductor digiti minimi. Statistics revealed a significant tic distributionxage interaction effect. Only in the 15-19 years subgroup, CSP was shorter in patients with distal tics in comparison to patients without distal tics (94.1+/-54.1 ms versus 135.2+/-36.8 ms at a stimulus intensity of active motor threshold plus 30%). Inhibitory processes in the sensorimotor circuit could reflect developmental aspects of tic phenomenology, particularly tic distribution during adolescence.