Resting tremors associated with Parkinson's disease (PD) remains difficult to quantify and track during disease progression. This study propose to explore the rhythmicity of distal muscle contractions in the upper limb to characterize resting tremor and discriminate it from cerebellar tremor (CT) based on the frequency spectrum of the EMG signal.

This retrospective study analyzed surface EMG recordings of wrist flexor-pronators and extensor-supinators from patients with PD or CT bilaterally in five 10-second conditions: rest with contralateral motor distraction, symmetrical arms extended forward posture with hands pronated, semi-pronation, supination, and elbows flexed with hands pronated. The rhythmicity index (RI) is calculated from the ratio of the area of the maximum power peak to the total area of the spectrum between 1.5-12Hz.

Inclusion Criteria:

• patient who performed surface EMG recordings of wrist flexor-pronators and extensor-supinators in Laboratories;
• diagnosis of Parkinson's disease or cerebellar tremor.

Exclusion Criteria:

• Botulinium toxin injection in upper limb during a delay of 3 months before surface EMG recordings;
• Levodopa drugs administrated during a delay of 12 hours before surface EMG recordings;
• Tremor-favour drugs administrated during a delay of 30 days before surface EMG recordings;
• Presence of an other neurologic disease or of any disease associated with motor disorders in upper limb.

Patients with Parkinson's disease or cerebellar tremor diagnosis.