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November 1997

Subcortical Reflex Myoclonus?

Author Affiliations

Department of Neurology, Faculty of Medicine University of Tokyo 7-3-1, Hongo, Bunkyo-ku Tokyo 113, Japan

Arch Neurol. 1997;54(11):1323-1324. doi:10.1001/archneur.1997.00550230006004

The article by Cantello et al1 titled "Focal subcortical reflex myoclonus" proposes a new physiological type of myoclonus. As the authors mentioned, their results were almost the same as those in our previous article.2 However, their conclusion is different from ours.

Their discussions are mainly based on the latency comparisons among different methods. They estimated the efferent conduction time (motor cortex to muscle) for myoclonus as the latency of a myoclonus-sized electromyographic response evoked by cortical stimulation in the relaxed muscle, which must be the latency of some later I wave. It may or may not be true. During relaxation, electromyographic response occurs when a later I wave arrives at the motor neurons because temporal summation of multiple descending volleys evoked by cortical stimulation are necessary for activation of motor neurons. However, an extremely large descending volley produced by an abnormal epileptic spike in the motor cortex may

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