Polymyographic recordings of tremor and myoclonus in two patients with ARCA2 demonstrating the effect of ubidecarenone therapy. Patient #3: note the erratic myoclonus (*) obtained in SCM muscles (90 ms), during writing (A). Dystonic tremor (arrow), can be seen in posterior muscles (right and left splenius), intermingled with myoclonus (◊). All these abnormalities were absent after treatment (B). Patient #4: left upper limb recording performed during spiral drawing displayed a 6 Hz regular tremor (arrow), composed of 120 ms length bursts, alternating in antagonistic forearm muscles (ECR/FCR), associated to an oscillatory signal in Acc (C). Note the dramatic attenuation of tremor amplitude after treatment on spiral drawing (D, before treatment and E, under ubidecarenone), as well as on polymyographic recording (F, under treatment). Abbreviations: r: right, l: left, SCM: sterno-cleido-mastoideous, ECR: extensor carpi radialis, FCR: flexor carpi radialis, FDI: first dorsal interosseous muscles, Acc: accelerometer.