Jerk-locked premyoclonus spikes UMLS:C3552825 Jerk-locked averaging (JLA) is used to record the timing and distribution of brain activity preceding brisk involuntary movements such as those observed in patients with myoclonus. JLA is capable of revealing a premyoclonus spike in the absence of paroxysmal activity in the routine EEG. HP:0001351 EEG-EMG jerk-locked averaging is a technique that combines EEG and EMG to assess myoclonus. The technique use electromyography (EMG) electrodes for the arms or legs, and correlates averaged EEG responses with EMG bursts used as a trigger. Abnormality of central nervous system electrophysiology