Motor Excitability after the C Reflex in Cortical Reflex Myoclonus

Abstract

Twelve patients with cortical reflex myoclonus were electrophysiologically investigated. From the results of the recording of the C reflex during voluntary contraction, cortical reflex myoclonus was classified into three subtypes: type Ⅰ; C reflex with recurrent C reflex (C'), type Ⅱ; double C reflexes (C1, C2) and type Ⅲ; C reflex with evident inhibition. The jerk-locked motor evoked potential (MEP) showed different mechanisms in the C'and C2 reflexes. The findings of cortical delay, facilitatory effect of peripheral stimulation on MEP and jerk-locked MEP indicate that both cortical reflex myoclonus and the silent period after the C reflex in patients with type Ⅲ cortical reflex myoclonus might originate from a change of cortical excitability of the motor cortex.