The purpose of this study is to determine whether transcranial direct current stimulation (tDCS) delivered over the motor cortex or the cerebellum can improve essential tremor and to identify the cerebral mechanisms involved in these potential effects.

Inclusion Criteria:

• Age ≥ 18 years and < 50 years
• Important essential tremor (bilateral postural and/or action tremor since more than one year)
• Normal physical and neurological examination, except for essential tremor
• Insufficient efficiency of usual essential tremor's treatment
• No treatment altering the cortical excitability
• Agreement to use a medically acceptable method of contraception throughout the study for female of childbearing potential

Exclusion Criteria:

• Cervical tremor
• Current neurological or psychiatric illness other than essential tremor
• Individual who is on medication which is known to lower seizure threshold
• Previous history of seizure(s), malaise or current active epilepsy
• Contraindication for MRI or TMS study
• Pregnancy, breast feeding women and women who are of childbearing age and not practicing adequate birth control
• Individual who have MMS ≤ 24/30 or patients legally protected or inability to provide an informed consent
• Simultaneous participation in another clinical trial
• Patients who are not enrolled at social security