Combined Phase II/III, multi-center, prospective, single-blinded trial.

Ten (10) patients with who previously underwent successful and uncomplicated MRgFUS thalamotomy for essential tremor will undergo a contralateral treatment. The incidence of side effects will be determined at 1 and 3 months postoperatively, graded per the CTCAE v5 and analyzed by a data safety monitoring board. Upon successful review, this Phase II trial will be converted to a Phase III trial of utility that will enrol 40 additional patients. The primary outcome will be the change in QUEST score at 12 months postoperatively, as well as a patient-reported assessment of Health Utility. Secondary outcomes will include objective tremor, gait and speech assessments (filmed and scored by blinded evaluators), as well as quality of life questionnaires and adverse events questionnaires. Outcomes will be assessed immediately after the procedure, as well as 1, 3, 12, 24 and 36 months post-operatively.

Inclusion Criteria:

• Patients must be ≥ 18 years
• The patient has a primary diagnosis of ET or ET plus confirmed by a movement disorder neurologist;
• The patient previously underwent a MRgFUS (> 6 months ago);
• The tremor on the untreated side negatively impacts the patients' quality of life;
• The patient wants treatment of the contralateral side.

Exclusion Criteria:

• Clinically relevant gait and/or balance impairment (e.g. wide-based, more than 2 falls/months, wheelchair, walker, cane use)
• Clinically relevant speech impairment (e.g. impairment of intelligibility)
• Inability to comply with the follow-up schedule;
• Refusal of the treating physician.

All assessments filmed on video and scored by a blinded evaluator.