P244 Normal cortical modulation of subcortical structures is altered in cervical dystonia

Abstract

Objective Blink reflex (BR) is obtained after different kinds of stimuli, such as trigeminal supraorbial branch stimulation (trigeminal BR, TBR) or median nerve stimulation at wrist (hand-evoked BR, HBR). Inhibition of TBR occurs when a preceding subthreshold stimulus is applied before trigeminal stimulation (prepulse inhibition, PPI). In healthy subjects, magnitude of HBR is increased and magnitude of PPI of TBR is decreased if the stimulated hand is positioned in the peripersonal space (PPS). Here, we aimed to investigate the changes of HBR and PPI of the TBR in PPS to understand alterations of cortical modulations of subcortical structures in cervical dystonia. Patients and method We recruited 23 consecutive patients with idiopathic CD and 21 healthy subjects. All participants had HBR and age and gender were similar between groups. HBR and PPI of the TBR were recorded while stimulated hand was in the extrapersonal space (far condition) and in the PPS (near condition). Baseline values were compared between patient with CD and healthy subjects. Further comparisons were done between far and near conditions. Results Magnitude of baseline HBR was bigger in patients with CD compared to healthy subjects. The magnitude further increased in healthy subjects whereas it was reduced in patients with CD. In healthy subjects, prepulse stimulation led to the reduced magnitude of R2 component of BR under far condition whereas the reduction was less evident under near condition. Although prepulse inhibition was low in patients with CD compared to healthy subjects, the reduction was more evident under near condition in patients with CD. Discussion Enhancement of HBR and attenuation of PPI of the TBR in the PPS is a normal phenomenon that provides evidence for top-down modulation of the neural circuitry underlying these reflexes. In CD, these normal alterations are lost which suggest abnormal modulation of higher-order centers.