Patient description: A 22-year-old Caucasian man came to the Clinic with a history of tremors since a year ago. The tremor was first in his right hand while holding something. Later the tremor became continuous and extended to both hands and legs and even at rest. The Kayser-Fleischer' ring was detected in the ophthalmologic exam. The physical exam revealed jaundice, hepatosplenomegaly and hypotonia of the upper limbs. He had a constant smile on his face, however, he has aggressive behavior according to his parents' explanation. His laboratory study was significant for a low serum caeruloplasmin (0.05 g/l), and a raised 24 hour urine copper excretion (120 μg/24 h). Wilson disease was confirmed by high liver copper concentration (305 μg/g dry weight of liver).

Clinical trial eligibility criteria: eligible ages (years): 21.0-70.0,  Essential Tremor Subject population (children, adults, groups): Adults approved for DBS surgery at Mayo Clinic for treatment of essential tremor Prospective subjects must meet all of the following to be eligible for study participation Must be greater than or equal to 21 years of age. Must be approved for DBS surgery at Mayo Clinic for treatment of essential tremor Competent and willing to provide signed, informed consent to participate in the study Stable dose of tremor medications, if applicable, for 30 days prior to study entry Stable dose of antidepressant medications, if applicable, for 90 days prior to study entry Willing to comply with study protocol requirements including: remaining on a stable dosage of tremor and antidepressant medications, if applicable, during the duration of the study; no significant alcohol or caffeine consumption within 8 hours of study visits; no usage of the Cala TWO device within 8 hours of study visits  Prospective subjects that meet any of the following are not eligible for enrollment in this study Moderate to severe ethanol dependence as defined by the outlined in the DSM-5 (score of 4 or higher) Implanted electrical medical device, such as a pacemaker, defibrillator, or deep brain stimulator Previous thalamotomy procedure, including stereotactic thalamotomy, gamma knife radiosurgical thalamotomy, and focused ultrasound for the treatment of tremor Suspected or diagnosed epilepsy or other seizure disorder. Swollen, infected, inflamed areas, or skin eruptions, open wounds, or cancerous lesions of skin at stimulation site (wrist) Peripheral neuropathy affecting the tested upper extremity. Presence of any other neurodegenerative disease like Parkinson plus syndromes suspected on neurological examination. These multisystem atrophy, progressive supranuclear palsy, dementia with Lewy bodies, and Alzheimer's disease Anyone suspected to have the diagnosis of idiopathic Parkinson's disease (PD). This includes excluding anyone with the presence of parkinsonian features including bradykinesia rigidity, or postural instability. Subjects that exhibit only mild resting tremor but no other symptoms or signs of PD may be included Botulinum toxin injection for hand tremor within 6 months prior to study enrollment Are participating or have participated in another interventional clinical trial in the last 30 days which may confound the results of this study, unless approved by the Principal Investigator Significant alcohol or caffeine consumption within 8 hours of study enrollment, which may confound the results of the study, where significant caffeine is considered more than 95 mg (equivalent to a cup of coffee), and significant alcohol is considered more than 14 g (equivalent to 5 oz of wine, 12 oz of beer, or 1.5 oz of distilled spirits)