The Swedish Essential Tremor (SWEET) Trial - A Multicentre Randomized Controlled Trial of Deep Brain Stimulation for Essential Tremor

PURPOSE AND AIMS

• Aim 1 - To evaluate the effect of deep brain stimulation (DBS) vs best medical treatment in essential tremor (ET) in a randomized, single-blinded controlled trial.
• Aim 2 - To compare the effect of DBS in the established target in the ventrolateral (VL)-thalamus/ nucleus ventralis intermedius thalami (Vim) and in a new target in the posterior subthalamic area (PSA)/caudal Zona incerta (cZi).
• Aim 3 - To map the target area in the VL-thalamus and PSA concerning effects and side effects of stimulation in order to identify and delineate the optimal target.
• Aim 4 - To evaluate the long-term effects of DBS for ET in a longitudinal non-randomized evaluation.

SURVEY OF THE FIELD Deep Brain Stimulation (DBS) In DBS, thin quadripolar electrode leads (with four 1.5 mm long and 1.27 mm thick contacts, separated by 1.5 mm space), connected to a neuropacemaker are implanted with stereotactic technique into the central parts of the brain where the neuronal activity is modulated with electrical current. DBS has revolutionized the treatment of Parkinson´s disease and other movement disorders, and more than 150.000 patients have so far been operated. Currently, new indications and targets are emerging.

However, many of the brain targets subjected for DBS are not well defined, and one of the main problem with DBS is likely to be the high number of suboptimal placed electrodes with lack of effect, unacceptable side effects and costly revisions. Further, even though this is an invasive and highly resource demanding therapy, most clinical indications for DBS (asides from Parkinson´s disease and dystonia) are not evidence based. They are considered as "established treatments" and often provided as clinical treatment and not within the context of trials or scientific studies.

DBS for Essential Tremor ET is the most common adult movement disorder with a prevalence of about 5% in the population above 65 years of age. Of patients who seek medical care up to 50% do not respond adequately to drug therapy.