Movement-related desynchronization-synchronization (ERD/ERS) in patients with Unverricht–Lundborg disease

Abstract

We studied changes in event-related desynchronization/synchronization (ERD/ERS) patterns in patients with Unverricht–Lundborg disease (ULD), presenting with prominent action myoclonus. We analyzed the movement-related ERD/ERS in α and β frequency bands in 15 patients using self-paced finger extension as a motor paradigm and we compared the results with those obtained in 12 healthy volunteers. In all ULD patients, α- and β-ERD regularly occurred with onset and location similar to that found in healthy controls, but the desynchronization of α activity was significantly greater than in controls (C3: − 64.4 ± 9.8% vs. − 49.7 ± 14.8%; p = 0.004). Moreover, in the patients, both α- and β-ERD spread toward frontal electrodes. In controls, the post-movement β-ERS regularly occurred; it was absent in eight patients with severe action myoclonus, while, in seven patients with mild or moderate myoclonus, the β-peak was significantly smaller with respect to that measured in controls (55.6 ± 15.1% vs. 153.9 ± 99.8%, p = 0.006). The failure of β-ERS well-correlated with motor impairment resulting from action myoclonus, whereas SSEPs and long-loop reflexes performed to detect signs of cortical hyperexcitability showed inconsistent changes. In ULD patients, ERD/ERS changes indicate an increased activation of motor cortex during movement planning and a great reduction of post-excitatory inhibition of motor cortex. The changes involving β-ERS had a significant relationship with the functional disability in individual patients and might play a pathogenic role in the motor dysfunction.