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OBJECTIVE: Recent diagnostic criteria for functional movement disorders have proposed a "laboratory supported" level of diagnostic certainty where the clinical diagnosis is supported by a positive test. For functional myoclonus the Bereitschaftspotential (BP) is generally accepted as a positive laboratory test. We hypothesised that a different EEG measure, event-related desynchronisation (ERD), might be more effective. METHODS: We analysed 20 patients with functional propriospinal myoclonus (fPSM) and 9 controls with organic myoclonus and performed back-averaging for BPs plus time-frequency decomposition to assess ERD and calculated sensitivity and specificity for both techniques. RESULTS: The BP was present in only 25% of patients with fPSM while the majority showed a significant ERD (mean 38 Hz; sensitivity 65%). ERD was significant at the group level (p < 0.001), but not the BP (p > 0.05). Both BP and ERD were absent in our control group. CONCLUSION: ERD in high-beta may be a useful new test for positive diagnosis of functional myoclonus.

Original publication




Journal article


Parkinsonism Relat Disord

Publication Date





116 - 118


EEG, Myoclonus, Adult, Aged, Contingent Negative Variation, Electroencephalography, Electromyography, Evoked Potentials, Female, Humans, Male, Middle Aged, Myoclonus, Young Adult