Fourteen patients with SD (11–63 years) and 18 age-matched normal subjects (11–51 years) were studied. Among the 14 patients with SD, 8 patients had SD-P and 6 had SD-A. Using median nerve stimulation at the wrist, the amplitude of the frontal N30 (FrN30) was compared between pre-movement and rest conditions.
We found that the amplitude of the contralateral FrN30 was attenuated before movement in normal controls and in the majority of both SD types. On the other hand, the pre-movement-rest amplitude ratio in patients with SD-A was significantly larger than in patients with SD-P (P = 0.0025). No significant differences were observed in the pre-movement-rest ratio between SD-P and normal subjects.
The preservation or impairment of pre-movement gating shown here suggests a physiological difference between the two types of SD. More specifically, sensorimotor integration of the basal ganglia-thalamo-cortical circuits may be intact in SD-P, but are affected in SD-A.
We discuss the different pathophysiology seen in the different phenotype of SD based on the different developmental involvement in the basal ganglia.