OC17: Event-related modulation of sensorimotor cortex alpha/mu activity is abnormal in children with dystonia and dystonic cerebral palsy

Abstract

Sensorimotor processing is abnormal in adult genetic/idiopathic dystonia, but sparsely studied in acquired or childhood dystonia. We investigate sensorimotor processing by measuring event-related synchronisation (ERS) and desynchronization (ERD) in response to a proprioceptive stimulus in children with dystonia/dystonic cerebral palsy (CP). Methods: 30 young people with dystonia (20 genetic/idiopathic; 10 dystonic CP) and 22 controls participated, age 5-21years (mean 12.7years). Proprioceptive stimuli, comprising a brief stretch of the wrist flexors, were delivered to each hand using a robotic wrist interface. Scalp EEG was sampled (2500Hz). Wrist position was monitored and movement onset synchronised with EEG. Up to 160 epochs (1s pre- and 3.5s post-stimulus) were averaged per subject to produce a Stretch Evoked Potential. Time-frequency analyses were performed using continuous Morlet wavelet transforms (1Hz bins from 5-40Hz, 8 wavelet cycles). Relative changes in post-stimulus power with respect to pre-stimulus/baseline, were calculated for the alpha/mu (8-12Hz) band. Results: Controls showed a clear developmental profile in event-related spectral changes, with a prominent early alpha/mu ERD (0.5-1s post-stimulus) and later alpha/mu ERS (1.5–2.5s post-stimulus) over contralateral sensorimotor cortex. Control and dystonia groups were compared using age as a covariate. Alpha ERD was significantly smaller in dystonia for both the dominant (ANCOVA F(2,47)=4.45 p=0.017) and non-dominant hand (ANCOVA F(2,42)=9.397 p<0.001). Alpha ERS was significantly smaller in dystonia for the dominant hand (ANCOVA F(2,47)=7.786 p=0.001). Findings were similar for genetic/idiopathic dystonia and dystonic CP. Conclusions: The impaired alpha/mu modulation indicates a developmental abnormality of sensorimotor processing which is common to genetic/idiopathic dystonia and dystonic CP.