To assess ERP measures of social cognition in patients with cervical dystonia.

Cervical dystonia is a complex movement disorder characterised by sustained or intermittent muscle contractions that can present as twisting, repetitive or patterned movements and abnormal postures. It is a syndromic disorder, with evidence of motor and non-motor symptoms (psychiatric, cognitive and sensory). Recent evidence has suggested that abnormalities in social cognition are part of the non-motor syndrome of cervical dystonia. 

12 patients with cervical dystonia and 12 healthy controls were recruited to undergo 128 lead EEG recording while passively viewing a standardised facial expression images database.  The following ERPs were analysed during this task: P300, EPN, N170 and LPP. 

We noted several differences in ERPs between patients and controls. The P300 components showed the most robust changes, followed by the LPP. The N170 and EPN only showed differences in specific hemispheres. 

Processing of facial emotions is abnormal in patients with cervical dystonia. These subtle covert deficits indicate abnormalities in a network involving the superior colliculus and amygdala. This study provides evidence of cognitive dysfunction in cervical dystonia and lends credence to a network disorder theory of idiopathic focal dystonias.