P218 Motor cortical adaptation to external stimuli is altered in unverricht-lundborg type myoclonus epilepsy.

Objectives Unverricht-Lundborg disease, or progressive myoclonus epilepsy type 1 (EPM1), affects cortical excitability and inhibition, and neuroanatomy of the thalamocortical system. Stimulus sensitive myoclonus with potentially disabling features associates with EPM1. Our objective was to assess neurophysiological adaptation in EPM1 to further understand the role of the impaired thalamocortical system in the characteristic features of the disease. Methods Eight EPM1 patients and 10 controls were studied using navigated transcranial magnetic stimulation (nTMS). We studied adaptation of motor cortex to excitatory external stimuli using nTMS with repetition suppression (RS) study-protocol adapted from our previous study [1] . Results We found that the reactivity and adaptation to external stimuli was highly abnormal in EPM1 patients compared to healthy controls. EPM1 group exhibited no RS effect ( F = 1.07, p = 0.385), while such effect was observed in controls ( F = 53.01, p < 0.001 ). In controls, the RS effect was seen as 50–55% reduction in motor evoked potentials of the right hand after the first stimulus in RS stimulus protocol. Conclusions Neural processing of stimuli received by the motor cortex is severely impaired in EPM1. This may be due to anatomic changes seen in the thalamocortical system, potentially impairing connective control between the thalamic nuclei and the cortex. Significance The abnormal adaption to external stimuli observed in the present study may contribute to the expression of the EPM1’s motor symptoms. This study helps to further understand the neurophysiological appearance of EPM1 in common neural functions. [ABSTRACT FROM AUTHOR]