The network sustaining action myoclonus: a MEG-EMG study in patients with EPM1.
BACKGROUND
To explore the cortical network sustaining action myoclonus and to found markers of the resulting functional impairment, we evaluated the distribution of the cortico-muscular coherence (CMC) and the frequency of coherent cortical oscillations with magnetoencephalography (MEG). All patients had EPM1 (Unverricht-Lundborg) disease known to present with prominent and disabling movement-activated myoclonus.


METHODS
Using autoregressive models, we evaluated CMC on MEG sensors grouped in regions of interests (ROIs) above the main cortical areas. The movement was a repeated sustained isometric extension of the right hand and right foot. We compared the data obtained in 10 EPM1 patients with those obtained in 10 age-matched controls.


RESULTS
As expected, CMC in beta band was significantly higher in EPM1 patients compared to controls in the ROIs exploring the sensorimotor cortex, but, it was also significantly higher in adjacent ROIs ipsilateral and contralateral to the activated limb. Moreover, the beta-CMC peak occurred at frequencies significantly slower and more stable frequencies in EPM1 patients with respect to controls. The frequency of the beta-CMC peak inversely correlated with the severity of myoclonus.


CONCLUSIONS
the high and spatially extended beta-CMC peaking in a restricted range of low-beta frequencies in EPM1 patients, suggest that action myoclonus may result not only from an enhanced local synchronization but also from a specific oscillatory activity involving an expanded neuronal pool. The significant relationship between beta-CMC peak frequency and the severity of the motor impairment can represent a useful neurophysiological marker for the patients' evaluation and follow-up.
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy. silvana.franceschetti@istituto-besta.it.
Silvana
S
Franceschetti
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
Laura
L
Canafoglia
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.|Department of Informatics, Bioengineering, Robotics and System Engineering (DIBRIS), University of Genova, Genova, Italy.
Fabio
F
Rotondi
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
Elisa
E
Visani
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
Alice
A
Granvillano
Department of Neurophysiology, Epilepsy Centre, C. Besta Neurological Institute IRCCS Foundation, Via Celoria 11, 20133, Milan, Italy.
Ferruccio
F
Panzica
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000503:physiopathology*; D011999:Recruitment, Neurophysiological; D020194:Unverricht-Lundborg Syndrome / Q000503:physiopathology*; D055815:Young Adult
Action myoclonus; Cortical network; Cortico-muscular coherence; MEG