Movement-related cortical potentials in patients with Machado-Joseph disease

Movement-related cortical potentials (MRCP; nomenclature of MRCP components according to Shibasaki and Hallett (Shibasaki H, Hallett M. What is the Bereitschaftspotential? Clin Neurophysiol 2006;117:2341-56) were studied in patients with Machado-Joseph disease (MJD) to elucidate the pathophysiology of voluntary movement.

We studied nine genetically proven MJD patients and eight age-matched healthy subjects. Multi-channel electroencephalogram (EEG) recordings were obtained during self-paced fast extensions of the wrist. EEG epochs were time-locked to electromyography (EMG) onset or offset of the voluntary EMG burst and averaged.

In the MJD patients, the early Bereitschaftspotential (early BP, -1500 to -500ms) was not affected but the late BP was reduced over the central midline area and contralaterally to the movement side. The amplitude of the fpMP, a post-movement MRCP component, was also reduced. In addition, the offset cortical potential in the first 500ms after EMG offset (Moff+500) was attenuated bilaterally over a wide cortical area.

Findings suggest that cortical activations associated with the initiation and termination of a voluntary movement are impaired in MJD patients.

Abnormalities of pre- and post-movement MRCP components provide researchers with pathophysiological insight into voluntary motor dysfunction in MJD.