Long-Term Transcutaneous Stimulation and Essential Tremor: A PET Study
Long-Term Transcutaneous Stimulation and Essential Tremor: A PET Study
Essential tremor (ET) is the most common movement disorder in the United States and affects
 up to 5% of the population. ET patients experience involuntary shaking of the hands, head
 and/or voice that can range from mildly limiting to severely disabling.

 Treatment options are limited and there are currently no medications specifically designed to
 treat it, and medications that are prescribed to relieve tremors are often limited by either
 inadequate efficacy or intolerable side effects. A subset of essential tremor patients whose
 tremors are inadequately treated by medication choose to undergo deep brain stimulation (DBS)
 of the ventral intermediate thalamic nucleus. DBS has been shown to be highly effective for
 tremor suppression. However, DBS carries significant risks. As a result, a very small (less
 than 3%) percentage of essential tremor patients undergo DBS therapy.

 The medical technology company Cala Health has developed a wristband device (the Cala TWO)
 that offers individuals with essential tremor a novel non-pharmacological, non-invasive
 alternative, in the form of stimulation of peripheral nerves, to aid in hand tremor relief.
 This innovative form of therapy has the potential to have important health, quality of life,
 and economic benefits for essential tremor patients.

 The present pilot study (Aim 1) will assess the effectiveness of 3-month twice daily
 treatment with the Cala TWO device to aid in the relief of hand tremors in adult essential
 tremor subjects that have been approved to undergo deep brain stimulation surgery at Mayo
 Clinic - Rochester. This study is a prospective, within subject, non-significant risk study
 at Mayo Clinic - Rochester, enrolling approximately 20 subjects.

 A completely optional component of this study (Aim 2) is seeking to perform three standard
 PET/CT sessions on a subset of these subjects (n=10) at Mayo Clinic - Rochester to evaluate
 changes in brain metabolic activity as a result of 3 months treatment with the device. The
 first session would take place upon a subjects entry into the study (start of month 1) and
 prior to any treatment with the Cala device, a second the following day after a 40 minute
 treatment period with the Cala device, and a third session at the end of the third month.
 This study is a prospective, within subject, greater than minimum risk study.
Hypothesis:

 The primary research question is whether customized patterned transcutaneous afferent
 electrical stimulation to the median and radial nerves via the Cala TWO wrist-band device
 significantly reduces hand tremors in individuals diagnosed with essential tremor that have
 been approved as candidates for deep brain stimulation (DBS) surgery. A second research
 question is whether three months of treatment with the Cala TWO device leads to significant
 changes in regional brain metabolism that is associated with therapeutic efficacy.

 Aims, purpose, or objectives:

 Aim 1: Determine the clinical efficacy of the Cala TWO device to transiently reduce hand
 tremors in the treated hand of subjects with essential tremor (n=20) over a three month
 treatment period prior to their undergoing DBS surgery for treatment of essential tremor at
 Mayo Clinic.

 Aim 2: Compare regional brain metabolism between baseline, after acute stimulation with the
 Cala TWO device, and at exit 3 months after therapeutic treatment with the Cala TWO device.
 18Ffluorodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computerized Tomography (CT)
 scans will be applied in a subset (n=10) of essential tremor subjects to evaluate changes in
 brain tissue metabolic activity corresponding to regional glucose uptake.

 Aim 1 Methods:

 Design of the Cala TWO device Study: Subjects will be recruited exclusively from adult
 essential tremor (ET) patients that have been approved by Mayo Clinic Deep Brain Stimulation
 Group (comprised of neurosurgeons, neurologists, psychiatrists, and radiologists) to undergo
 deep brain stimulation surgery at Mayo Clinic - Rochester for the treatment of ET. As such,
 subjects that consent to this study are expected to readily meet the pre-specified inclusion
 criteria noted below for participation in the study.

 Regardless, all subjects will be pre-screened against the inclusion/exclusion criteria
 through face-to-face interviews. Additionally, baseline function and tremor severity will be
 collected in the first visit phase of the study. Subjects already taking medications for ET
 will be permitted these medications during the study with no changes in medication type or
 dosage.

 All subjects will be fitted with a Cala TWO device based on the subject's wrist circumference
 (small, medium, or large) and stimulation hand (right or left) at the beginning of the study
 visit. The stimulation hand will be the hand with more severe tremor (or the dominant hand if
 both hands had equal tremor severity) as determined by the TETRAS task completed during the
 baseline evaluation and pre-surgery clinical evaluation by the Mayo Clinic DBS group. Once
 the Cala TWO device has been fitted to the subject's hand a frequency calibration procedure
 will be conducted in which the subject's tremor frequency will be determined while the
 subject performs a forward postural hold task. This frequency will then be incorporated into
 the therapeutic stimulation waveform.

 Stimulation will consist of a series of charge balanced biphasic pulses delivered at a
 frequency of 150 Hz, 300 µs pulse width, and 50 µs inter-pulse period. The stimulation will
 be alternated between the median and radial nerve at a frequency equal to tremor frequency
 (i.e. for a measured 5 Hz tremor frequency, stimulation will be applied over the median nerve
 for 200 msec, then alternated to be applied over the radial nerve for 200 msec). To determine
 the stimulation amplitude, the site study neurologist will increase the stimulation level by
 0.25 mA steps until the subject reports sensation of the stimulus in areas in the hand or
 finger area. Final stimulation amplitude will be chosen to be the highest level of
 stimulation below muscle contraction that the subject finds comfortable (mean: 5.4 mA +/-
 2.9). Once the maximum tolerable stimulation level has been identified, subjects will receive
 stimulation at that level during the 40-minute stimulation session. Adverse events will be
 collected before, during, and after each stimulation session. Subjects will then receive
 device training and instructions by on-site study personnel for conducting daily home
 stimulation sessions.

 Power Statement: This is a pilot study with a unique subject cohort.

 Data Analysis Plan:

 An analysis of covariance (ANCOVA) model will be used to assess the statistical significance
 of the difference in the mean change in tremor before and after treatment.

 Efficacy will be measured as the change in the TETRAS scale measure of upper limb tremor
 following stimulation compared with pre-stimulation. Additional analyses will include the
 Bain & Findley 4-point scale assessment of typical Activities of Daily Living (ADL) and the
 Patient Global Impression - Severity (PGI-S) 7-point scale of the subjects' personal
 assessment of how much their tremor level improved or worsened relative to their baseline
 state prior to the stimulation session.

 The primary safety endpoint will be an analysis of adverse events types and rates for all
 enrolled subjects, where the adverse event rate will be calculated as the percentage of total
 subjects with an adverse event.

 Aim 2 Methods:

 The investigators propose to recruit subjects (n=10; age 21-70) from the population of
 subjects that have enrolled in the Cala TWO device which is a 3-month treatment duration
 study with the Cala TWO device prior to subject's scheduled deep brain stimulation surgery.
 This optional component of this study will perform three standard PET/CT sessions on these
 subjects at the Mayo Clinic Molecular Research Imaging Facility to evaluate changes in brain
 tissue metabolic activity as a result of 3 months treatment with the device. The advanced
 clinical PET scanner PET/CT will be used in this study, equipped with digital silicon
 photomultiplier detectors.

 First session: Takes place upon a subject's entry into the Cala TWO study (start of month 1)
 and prior to any treatment with the Cala device.

 Second session: Takes place the following day after a 40 minute treatment period with the
 Cala device.

 Third session: Takes place at the end of the third month of use of the device.

 Minimizing the Radiation Risk: By using an advanced clinical PET scanner, equipped with
 digital silicon photomultiplier detectors, the investigators will be using a reduced
 intravenous delivered dose of FDG (8 mCi).

 Attenuation Correction Scans: For PET/CT, a low-dose CT fusion skull scan (~1min) will be
 acquired for attenuation correction and anatomical co-registration.

 Step-by-Step Schedule:

 The FDG scan slots are available at 7:30am, 8:00am, 8:30am, and 10:30am. Participants with
 head tremor would present problems in obtaining quality scans. If this is the case, a head
 secure procedure will be included.

 1. A 4 hour fast is required prior to FDG injection. Patients are given instructions to
 remain well-hydrated and have a low carbohydrate diet 18 hours before their appointment.

 2. No significant alcohol or caffeine consumption and no usage of the Cala TWO device
 within 8 hours of a PET session.

 3. Blood sugar level will be checked by a finger-poke blood test. Fasting blood glucose
 should be under 200 mg/dL.

 4. Women of child-bearing potential will go through a urine-pregnancy test, unless there is
 proof of negative results within 48 hours before the exam.

 5. 8 mCi FDG injection through IV and rest at the uptake room (eyes open in a dimly lit
 room).

 6. At 30 minute uptake time, conduct a PET/CT scan for a 15 min. A 1 min CT fusion skull
 image will be acquired for attenuation correction and anatomical co-registration.

 Power Statement: This is a pilot study with a unique subject cohort.

 Data Analysis Plan:

 CortexID (GE Medical Systems, LLC) and MIMneuro (MIM Software Inc.) will be used to confirm
 quality control of the PET image. Additional quantitative analysis of PET images will be
 conducted using SPM, FSL, and Analyze. CortexID. This quantification procedure uses a
 patient-specific FDG z-score map derived by comparing the surface projection map (z-SPM) with
 an age- and sex-matched normal control FDG database.
Subject population (children, adults, groups): Adults approved for DBS surgery at Mayo
 Clinic for treatment of essential tremor

 Inclusion Criteria:

 -  Prospective subjects must meet all of the following criteria 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.

 Exclusion Criteria:

 -  Prospective subjects that meet any of the following criteria are not eligible for
 enrollment in this study:

 -  Moderate to severe ethanol dependence as defined by the criteria 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 include: 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).

 -  Subjects unable to communicate with the investigator and staff. Any health condition
 that in the investigator's opinion should preclude participation in this study.

 -  Pregnancy or anticipated pregnancy during the course of the study.