The study is a pilot feasibility study aimed at verifying that (1) tremor can be recognized using an accelerometer placed on the hand area and a data mining algorithm properly trained and (2) TENS applied in the hand area is able to acutely suppress hand tremor respect to the baseline.

The study includes 2 different groups: 9 patients with Parkinson's disease with resting tremor alone at the start of their disease (group1), and 5 patients with Essential Tremor (group2). For both groups, the study protocol includes an initial screening visit, in which, after enrollment, the patient's baseline is defined. The experimental session combines both tremor recording and a TENS stimulation treatment.

During the experimental session, the patient wears two devices able to record the upper limb's motion. These devices are commercially available wearable IMU sensors equipped with a triaxial accelerometer, a triaxial gyroscope and triaxial magnetometer. One device is located on the hand, the other on the wrist of the same upper limb, the dominant one. Patients are asked to perform the tasks of the WHIGET scale at baseline and during two different types of electrical stimulation (in a randomly assigned order).

For the recording part, the primary endpoint is the accuracy of the detection system measured as the number of correct detections of tremor episodes on the total tremor episodes recorded by the system (5 seconds windows). For the stimulation part, the primary endpoint is the reduction of upper limb tremor during the stimulation session compared to baseline.

Inclusion Criteria:

• Subject signed the approved Informed Consent;

• Subject is willing and able to complete the study procedures;

• Subject is ≥ 18 years of age;

• Subject has a certain diagnosis of:

  • definite PD, at the start of the disease (respecting the new International Parkinson Disease and Movement Disorder Society diagnostic criteria) and experiences tremor as measured on the UPDRS Part III; or
  • ET;

• Subject has a normal cognitive function (MMSE ≥ 24 or MoCA >26).

Exclusion Criteria:

• Atypical parkinsonian syndromes - progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration, dementia with Lewy bodies, vascular Parkinsonism, and other rare causes;
• Other pre-existing and active major neurological disease;
• Pre-existing and active (e.g., on chronic medication) major psychiatric disease, such as major depression, schizophrenia, bipolar disease;
• Advanced liver, kidney, cardiac, or pulmonary disease, cancer;
• A terminal medical diagnosis consistent with survival < 1 year;
• Medical implanted devices (e.g. DBS, DUOPATM infusion pump); metal implants; the presence or even a suspicion of metal fragments or moving metal implants in its head or neck, as well as it had prior surgical operations on the head or neck;
• Dermatological lesions in the area to be treated with the electrical stimulation;
• Major drug dependency, including alcohol (in the investigator's judgment);
• Females who are pregnant or lactating;
• Subject had an important head injury in the past