Abnormal reactivity of the approximately 20-Hz motor cortex rhythm in Unverricht Lundborg type progressive myoclonus epilepsy.
The approximately 20-Hz component of the human mu rhythm originates predominantly in the primary motor cortex. We monitored with a whole-scalp neuromagnetometer the reactivity of the approximately 20-Hz rhythm as an index of the functional state of the primary motor cortex in seven patients suffering from Unverricht-Lundborg type (ULD) progressive myoclonus epilepsy (PME) and in seven healthy control subjects. In patients, the motor cortex rhythm was on average 5 Hz lower in frequency and its strength was double compared with controls. To study reactivity of the approximately 20-Hz rhythm, left and right median nerves were stimulated alternately at wrists. In controls, these stimuli elicited a small transient decrease, followed by a strong increase ("rebound") of the approximately 20-Hz level. In contrast, the patients showed no significant rebounds of the rhythm. As the approximately 20-Hz rebounds apparently reflect increased cortical inhibition, our results indicate that peripheral stimuli excite motor cortex for prolonged periods in patients with ULD.
Silén
T
T
Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, FIN-02015 HUT, Espoo, Finland.
Forss
N
N
Jensen
O
O
Hari
R
R
D000293:Adolescent; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D009044:Motor Cortex / Q000502:physiology*; D020191:Myoclonic Epilepsies, Progressive / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D013003:Somatosensory Cortex / Q000503:physiopathology