Fig. 4

a CC analysis of the right arm tremor polygraphy recordings from case 8. This reveals typical sinusoidal oscillations at a frequency of around 6 Hz with a mainly out of phase relationship between antagonist muscles in the forearm (FCU/EDC) and out of phase activation between proximal and distal muscles. The right FCU was used as reference (i). FFT analysis (blocks of 4096 data points at a resolution of 0.5 Hz) was implemented on the EMG recordings while maintaining antigravity posture; it reveals a tremor at 5.9 Hz with its first harmonic (ii). Same analysis after loading the hand initially with 0.5Kg (iii) and then with 1 kg (iv) does not show any modification to the peak frequency of the tremor, as expected for a centrally driven tremor. The electrophysiological findings from Case 8, shown in (a) versus another patient with cortical myoclonic tremor, case 7 shown in (b). The arrows show the contralateral to EMG biphasic cortical transients on the averaged EEG data in the central areas. The EMG polygraphy shows co-activation of proximal and distal muscles (i). The horizontal dotted lines in the central derivations represent the 95% confidence interval; the biphasic cortical transient preceding by few milliseconds the peak of the autocorrelation from the EDC is outside the 95% margins (ii). The cortico-muscular latencies for case 7 are shown at a slower sweep time in the relevant Additional file 1. Noticeably, the cross-correlation analysis in a and b show the regular sinusoidal oscillations in the former, typically seen in tremors, and in the latter, the synchronous proximal and distal activation that can be expected in cortically driven myoclonus. ADM = abductor digiti minimi, APB = abductor pollicis brevis, BB = biceps brachii, Del = deltoid, FCU = flexor carpi ulnaris, EDC = extensor digitorum communis, TB = triceps brachii, Tra = trapezius