Medical Policy

This document addresses external upper limb tremor electrical stimulators of the peripheral nerves, also known as transcutaneous peripheral nerve stimulation (TPNS) and transcutaneous afferent patterned stimulation (TAPS), for the treatment of upper-limb tremors. This non-pharmacological/non-surgical treatment option is proposed to aid in the temporary relief of essential tremor (also known as, familial essential tremor or hereditary tremor) of the hand, as well as other movement disorders including Parkinson disease.

Note: Please see the following related document for additional information:

• SURG.00026 Deep Brain Stimulation and Responsive Neurostimulation

Note: For a high-level overview of this document, please see “Summary for Members and Families” below. 

Investigational and Not Medically Necessary:

External upper limb tremor stimulator devices are considered investigational and not medically necessary for all indications, including but not limited to the treatment of essential tremor of the hands and Parkinson disease.

This document describes clinical studies and expert recommendations, and explains whether external upper limb electrical stimulators of the peripheral nerves for the treatment of tremors are clinically appropriate. The following summary does not replace the medical necessity criteria or other information in this document. The summary may not contain all of the relevant criteria or information. This summary is not medical advice. Please check with your healthcare provider for any advice about your health.

Key Information

This document is about electrical stimulator devices that send mild electrical signals through the skin to nerves in the arm for the treatment of arm tremors. These devices are meant to give short-term relief of hand tremors in people with essential tremor and other movement disorders such as Parkinson disease. The treatment does not involve surgery or medicine, and at this time involves the use of bracelet or watch-like devices worn on the wrist. Studies suggest that some people may have less tremors for a short time after treatment, and some people say daily tasks feel easier. But the available research has important limits. Many studies were small, lasted only a short time, or did not compare the device with a fake treatment. Some newer studies showed possible benefit, but results have been mixed, and skin irritation or discomfort can happen. Better studies are needed to know if this treatment improves health over time.

What the Studies Show

These devices try to lower the degree of tremors by stimulating nerves in the wrist and arm. The goal is to change nerve signals linked to tremor. The main possible benefit is short-term tremor relief without surgery. This may help with tasks such as writing, eating, or pouring. Reported harms from the use of such devices were usually mild, such as itching, discomfort, or skin irritation. A few studies also reported burns, and one study reported a fall that may have been related to the device. This means the balance of benefits and harms is still not clear.

The currently known research results are mixed. Some studies found short-term improvement in tremor scores or daily activities. However, many of these studies were done with people who knew what treatment they were getting, had no fake-treatment comparison, had too few people, or followed people for only a short time, all of which make the results of the trials less likely to reflect the real risks and benefits of the device. An earlier device did not do better than placebo. A study in Parkinson disease had no comparison group, and some people improved on some tasks but not others. A newer 90-day study found better daily activity scores than fake treatment, which is encouraging. Even so, the authors said the overall evidence is still not enough to show clear, lasting health benefit. Better studies are needed to know if this treatment improves health.

Is this clinically appropriate?

External upper limb tremor stimulators are not clinically appropriate. This is because they have not been proven to improve health. Unnecessary or unproven tests can lead to needless worry, or to treatment that does not help.

(Return to Description/Scope)

Summary

Essential tremor (ET) is a common neurological disorder with unclear mechanisms, and devices using transcutaneous electrical stimulation have been developed and proposed to reduce tremor symptoms. While several devices have received FDA clearance for temporary tremor relief, the supporting evidence is limited and mixed. Some studies suggest short-term improvements in tremor severity and daily functioning, with generally mild adverse effects, but trials are limited by small sample sizes, short follow-up times, significant loss to follow-up and other methodological issues. Randomized controlled trials (RCTs) have shown inconsistent or modest benefits, and earlier versions of the technology failed to outperform placebo. Clinical guidelines provide little or no strong endorsement, often relying on expert opinion rather than robust evidence. Overall, despite promising preliminary findings, current research is insufficient to confirm long-term effectiveness or meaningful health outcomes, and more rigorous, well-designed studies are needed.

Discussion

Essential tremor (ET) is the most common neurological disorder among adults and is the most prevalent tremor disorder. The exact mechanisms of ET are not fully understood, however recent studies suggest that ET may be a neurodegenerative disorder. The use of electrical stimulation applied to the nerves of the upper limbs, also known as transcutaneous afferent patterned stimulation (TAPS) or transcutaneous peripheral nerve stimulation (TPNS), has been proposed to treat ET and other neurological conditions associated with tremor.

External upper limb tremor stimulation devices (Cala Trio/Cala kIQ^™ [Cala Health, Inc. Burlingame, CA]), are on-demand, non-invasive, wrist-worn devices that deliver individualized electrical stimulation to the median and radial nerves of the arm in people. One such device is the Cala Trio Therapy. The proposed action of this device is the delivery of TAPS to the ventral intermediate nucleus thalamus, a key relay point in the central tremor network, and one target of deep brain stimulation (DBS), an invasive treatment of ET. Noninvasive TAPS stimulation to the upper limb using the Cala Trio device is calibrated to an individual’s tremor pattern and the user can adjust its strength to account for daily variations in tremor activity. Cala kIQ is the next generation device subsequently developed by the manufacturer to treat action hand tremor for individuals with ET and Parkinson disease. Cala kIQ is also wrist-worn and utilizes TAPS technology. Cala kIQ is purported to sense an individual’s unique tremor and deliver individualized therapy; one therapy session lasts for 40 minutes and sessions may be completed as often as five times daily.

In October 2021, the U.S. Food and Drug Administration (FDA) granted 510k clearance for Cala Trio Therapy with the indication to aid in the temporary relief of hand tremors in the treated hand following stimulation in adults with ET. The device stimulates the nerves in the arm to disrupt the neural signals that cause essential tremor. In November 2022, the FDA granted 510k clearance for the Cala kIQ as a substantially equivalent device. The indications for use are to aid in the temporary relief of hand tremors in the treated hand following stimulation in adults with ET, and to aid in the temporary relief of postural and kinetic hand tremor symptoms that impact activities of daily living in the treated hand following stimulation in adults with Parkinson disease. Clearance of the Cala kIQ device for Parkinson disease was based on a single-arm, non-significant risk study that evaluated calibrated therapy in patients with Parkinson Disease who also had postural hand tremor. A total of 40 individuals were enrolled in the study. Across visits, individuals were assessed using an unvalidated subset of the Movement Disorder Society-Unified Parkinson Disease Rating Scale (MDS-UPDRS) dominant hand tasks, and activities of daily living (ADLs) based on an unvalidated subset of Bain and Finley-ADL (BF-ADL) tasks. There were no reports of device-related serious adverse events, and all were resolved with minimal intervention. As noted in the FDA 510(k) Premarket Notification summary:

These results were descriptive in nature, different patients showed improvement in different tasks tested. None of the patients showed improvement in all of the tasks tested and some of the patients showed no improvement in any of the tasks tested.

There is no data comparing the Cala kIQ device vs. a sham-control device in individuals with Parkinson disease, and insufficient evidence to assess how the device affects health outcomes.

The predicate device to the Cala Trio and the Cala kIQ was the CalaONE, which obtained De Novo designation from the FDA in May 2017 (DEN170028). According to the De Novo summary document, the CalaONE failed to show a benefit versus placebo (FDA, 2017).The FDA clearance for the Cala Trio therapy was supported by data from the Prospective Study for Symptomatic Relief of ET with Cala Therapy (PROSPECT; NCT03597100), a prospective, post-clearance, multicenter, single-arm, open-label clinical trial evaluating the safety and efficacy of wrist worn TAPS therapy over a 3-month period. Isaacson (2020) reported findings for 205 of 263 participants who enrolled in and completed the study. Participants were instructed to use Cala Trio therapy twice daily (in 40-minute sessions) for 3 months, including three in-clinic visits. The co-primary endpoints were clinician-related Tremor Research Essential Tremor Rating Assessment Scale (TETRAS) and patient-rated Bain & Findley Activities of Daily Living (BF-ADL) dominant hand score. Other study measures included “improvement in the tremor power detected by an accelerometer on the therapeutic device, Clinical and Patient Global Impression scores (CGI-I, PGI-I), and Quality of Life in Essential Tremor (QUEST) survey.” Eligibility criteria included participants ≥ 22 years of age, a confirmed diagnosis of ET by a movement specialist, a tremor severity score of 2 or above in the dominant hand or arm by any of the TETRAS upper limb items, and a minimum score of 6 across all upper limb items. A BF-ADL score of 3 or more in any one of the upper limb items, a mi­nimum subset score of 8 across all upper limb items, and stable dose of tremor and antidepressant medications were inclusion criteria. Participants were excluded if they had significant alcohol or caffeine consumption within 8 hours prior to the study enrollment, any implanted medical devices or implanted metal in the wrist to be stimulated, presence of other neurodegenerative disease like Parkinson-plus syndrome on neurological exam, suspected idiopathic Parkinson disease, including presence of parkinsonian features, suspected or diagnosed epilepsy or other seizure disorder, or previous thalamotomy procedure, including stereotactic thalamotomy, gamma knife radiosurgical thalamotomy, and focused ultrasound for the treatment of tremor. The authors reported that the study co-primary endpoints were met (p<0.00001), with 62% (TETRAS) and 68% (BF-ADL) of ‘severe’ or ‘­­­moderate’ individuals reported improving to ‘mild’ or slight’. These results excluded 58 participants that withdrew from the study. There were no serious adverse events reported. Device-related adverse events were reported to have occurred in 18% of participants, with 64% rated mild (itchiness, discomfort), 34% as moderate (electrical burn, significant discomfort), and 2% as severe (1 event, a fall, which was possibly device-related). The study did not find a relationship between concurrent ET medication usage and response to TAPS therapy (66% of participants were on a medication to treat tremor). While initial results look promising for use of TAPs therapy in individuals with ET of the upper extremities the mechanism of therapy remains unclear, and limitations of the study include lack of blinding, absence of a control group (or randomization), and a short duration of follow-up. The authors concluded “future work examining how these clinical trial results translate into the real-world setting would be valuable” and to “establish robust methods to longitudinally maintain a patient blind for peripheral neuromodulation therapies.” Two additional manufacturer sponsored clinical trials (NCT05540626, NCT05480215) regarding the Cala Trio device were completed in 2022, however, no results have been published as of the time of this review.

Castrillo-Fraile (2019) conducted a systematic literature review on devices aimed at suppressing simulated tremor, excluding robot studies. The review included 12 articles focusing on interventions like orthoses using biomechanical loading, neuromodulation with electrical stimulation, and external tremor cancellation devices, all targeting upper limb tremor control. The devices reported an average tremor attenuation of 50-98% (level of evidence III). However, interference with voluntary movements and portability were noted as main drawbacks. The authors concluded that the evidence on the efficacy of these devices is low.

Barath (2020) reported an interventional, open-label, single-group study investigating the changes in brain metabolism over 3 months of TAPS use in 5 ET (n=5) participants. Each participant received 40 minutes of TAPS treatment twice daily for 90 days. Brain metabolic activity and tremor severity were measured at baseline, and after 90 days using F-fluorodeoxyglucose (FDG) PET/CT and TETRAS. The participant’s tremor power and frequency were measured before and after therapy sessions. Inclusion criteria were ≥ 21 years of age and approved for DBS surgery by the Mayo Clinic DBS Committee for treatment of ET. Participants were excluded if they had alcohol dependence or had an implanted pacemaker, defibrillator, or deep brain stimulator. The mean age of the study participants was 70.2 ± 5.2 years, and the duration of ET ranged from 10 to 57 years (mean 32 ± 16.8 years). Participants enrolled for approximately 89.2 days ± 4.8 days and completed 136.2 ± 41.3 TAPS sessions; participant compliance was 77.3 ± 25.6 %. The FDG PET/CT results demonstrated areas of increased metabolism in the ipsilateral cerebellar hemisphere and decreased metabolism in the contralateral hemisphere following 90 days of therapy, compared to day 1 (p<0.05). Comparison of pre- and post-therapy measurements over 90 days showed decreased tremor power (p<0.0001), but no change in frequency. The day 1 TETRAS scores decreased from 6.5 to 4.1 following TAPS (p=0.05). The 90-day pre- and post-TETRAS scores also decreased from 4.9 to 4.1 (p=0.14 and p=0.05, respectively). No adverse events were reported. The authors concluded that longitudinal TAPS of the median and radial nerves affect brain metabolism in areas necessary for motor coordination which may cause ET. Study limitations included its small study population and weak power. Additional studies with robust methodology and power are needed to further elucidate the clinical mechanism of TAPS.

Yu (2020) reported a single-arm, open-label study, of 15 individuals with ET who received TAPS therapy. The aim was to evaluate the duration of tremor reduction. Inclusion criteria were individuals 22 years of age and older diagnosed with ET by an internist or neurologist. Participants performed four hand tremor-specific tasks (postural hold, spiral drawing, finger-to-nose reach, and pouring) from the Fahn-Tolosa-Marin Clinical Rating Scale (FTM-CRS) prior to, during, and 0, 30, and 60 minutes following TAPS therapy. Tremor severity was rated using the FTM-CRS, and simultaneously with wrist-worn accelerometers. The duration of tremor reduction was measured by improvement in the mean FTM-CRS score across all four tasks compared to baseline, and reduction in accelerometer-measured tremor power compared to baseline for each task. The results demonstrated that mean FTM-CRS scores improved for at least 60 minutes beyond the end of TAPS for 80% of participants. For the assessed tasks, tremor power improved for at least 60 minutes beyond the end of TAPS for over 70% of participants. The postural hold task had the most significant reduction in tremor power (median 5.9-fold peak reduction in tremor power) and had at least 60 minutes of improvement relative to baseline beyond the end of TAPS therapy for 73% of participants. No adverse events were reported. The authors concluded that tremor power is a valid, objective assessment metric, and that TAPS therapy may improve upper limb tremor symptoms for at least 1 hour post therapy which may improve ability to perform ADL’s in individuals with ET. The authors also noted that 5 of the 15 participants in this study who were on pharmacologic treatment for ET, may have ingested medication that could have influenced the duration of effect. The NIH considers TETRAS the superior ET assessment measure compared to FTM, stating “TETRAS has two main advantages over FTM in the assessment of tremor severity: (1) the absence of a ceiling effect in patients with severe ET, and (2) the inclusion of wing‐beating tremor” (2017). While the results of this study are promising, larger cohorts with similar ET tremor scales are needed to further evaluate the clinical utility of TAPS.

The American Academy of Neurology (AAN) published an evidence-based guideline update for the treatment of essential tremor that was last reaffirmed July 2025 (Zesiewicz, 2017). This document includes recommendations for pharmacologic agents and surgical interventions for individuals with ET. No recommendations for use of external upper limb tremor stimulator device as a treatment of ET are provided.

The International Essential Tremor Foundation’s (IETF) Essential Tremor in Adult Patients Guideline Advisory document (2021) recognizes Cala Trio therapy as a “optional add-on non-pharmacological/non-surgical treatment” in combination with first-line pharmacological approaches (propranolol, primidone), or prior to or in conjunction with second- or third-line pharmacotherapies (topiramate, gabapentin, other beta blockers, or benzodiazepines). However, the recommendations which were updated in 2026, remain based on expert consensus for Cala Trio therapy and are not supported by any evidence-based explanation.

Lu (2023) published a 3.4 year retrospective analysis of the TAPS device. A registry was utilized to identify 1,233 individuals that were prescribed TAPS for ET and had used the device beyond 90-days. The study evaluated the usage, effectiveness, safety, and durability of TAPS. The inclusion criteria were the prescriber indicated a diagnosis of ET and the individual had used TAPS beyond the 90-day trial period. Exclusion criteria for all analyses, except the survey, were; 1) individuals that completed an insufficient number of sessions, defined as having completed fewer than 10 sessions that were at least 20 minutes in duration, 2) individuals that had not completed 10 sessions of TAPS with accelerometry measurements free of motion artifact that could be used to measure effectiveness before and after therapy, and 3) accelerometry that was measured no longer than 15 minutes before or 15 minutes after therapy, and was started at least 120 minutes after a prior session (to minimize carry-over effects). Eight hundred eight individuals passed the exclusion criteria. However, another 81 were excluded for having no postural hold data and another 334 were excluded for having fewer than 10 sessions of postural hold data. Final effectiveness analysis was derived from data for the remaining 386 individuals. The results showed the average tremor power improvement ratio was 2.8, (64.3% reduction) based upon accelerometry data. Additionally, 49.8% of individuals showed at least 50% tremor reduction, and 88.1% had at least 50% of sessions with a tremor improvement ratio. Average device usage was 5.6 sessions per week and no habituation was reported. Sixty two percent of the survey respondents reported reduced medication utilization (no p-values provided). One safety-related complaint was reported in 10.2% of individuals (discomfort 5.3%, skin irritation 6.9%, and physical symptoms 1.9%) but no serious safety events were reported. The authors concluded that the results reinforced and extended prior efficacy findings regarding the safety, usage, and durability of TAPS for tremor management in patients with ET. However, the study is limited by several factors, including the wrist-worn accelerometry provided a proxy assessment of hand tremor amplitude, only adverse events that were reported by participants to the manufacturer were recorded, and the low response rate to the voluntary survey.

Isaacson (2023) performed a review of seven studies that assessed the response to TAPS in the high unmet need subgroup (defined as a severe tremor, non-responsive to medication, age ≥65 years) and early responders (defined as substantial TAPS tremor improvement in the first month). Two of the studies were randomized controlled trials (RCT [Lin, 2018 and Pahwa, 2019]) that delivered a single session of TAPS treatment or sham in 23 and 93 enrolled ET participants, respectively. Additionally, there were three open label single-arm studies (Yu, 2020, Isaacson, 2020, and Barath, 2021) which evaluated a single TAPS session in 15 participants, as well as two home-use studies that evaluated twice-daily TAPS sessions over 3 months in 263 and 5 participants, respectively. Two real-world evidence analyses were also performed using a device registry database in 321 participants (Brillman, 2022) and 1,223 participants (Lu, 2023), with participants using TAPS therapy as-needed in the home setting. The analyses were performed using previously collected TETRAS scores, BF-ADL scores, and tremor power. Differences in BF-ADL and TETRAS improvement were observed with TAPS over sham for the high unmet need subgroup in a RCT (p<0.001). Analysis of previous evidence demonstrated that early responders maintained effectiveness and usage at 3 and 12 months (p<0.001). The authors concluded that compared to the original study population, similar or superior effectiveness was shown in the high unmet need subgroup. Additionally, individuals who exhibited an early response to therapy achieved tremor reduction without developing therapy habituation over long-term usage. The studies addressed in this review were discussed above and found to have methodological weaknesses.

Dai (2023) reported a non-blinded, randomized, prospective study that evaluated the clinical benefit of adding TAPS treatment to Standard of Care (SOC) versus SOC alone. It is notable that this may have included anti-tremor medication therapies in some participants. Individuals received a TAPS device and were randomized 1:1 to either 1 month adding TAPS therapy to usual care (treatment arm, n=119), or usual care with tremor assessment only (SOC arm, n=123). Inclusion criteria were individuals diagnosed with ET, defined as having at least two medical claims with an ET diagnosis code at least 7 days apart in the last 3 years, or one claim with an ET diagnosis code followed by at least one dispensed pharmaceutical treatment that can be used for ET; aged 22 years or older; and individuals with health insurance. Exclusion criteria were a diagnosis of Parkinson, Alzheimer’s, dementia, epilepsy, thyroid disorders, implanted pacemaker, defibrillator, or deep brain stimulator, individuals who had undergone ET-related neurosurgery or magnetic resonance-guided focused ultrasound, used botulinum toxin in the upper extremity in the last 6 months, were pregnant, or had hand lesions at the stimulation site. The outcomes assessed were changes in tremor power measured by motion sensors on the device, and improvement in BF-ADL upper limb scores between treatment and SOC groups. The results demonstrated tremor power, expressed as a geometric mean, in the treatment arm (0.017 (m/s²)²) was lower than tremor power in the SOC arm (0.08 (m/s²)²) in the modified intention to treat group (p< 0.0001), as well as in the per protocol analysis, (p< 0.0001). One hundred thirty four of the 276 individuals completed the BF-ADL ratings at baseline and 1 month. The changes in BF-ADL scores from baseline to 1 month in the treatment arm (1.6, n=51) were greater than the changes observed in the SOC arm (0.22, n=83), (p=0.0187). One hundred fourteen of the 242 individuals in the per-protocol analysis completed the BF-ADL ratings at baseline and 1 month. The changes in BF-ADL scores in the treatment arm (1.5, n=47) were greater than changes observed in the SOC arm (-0.1, n=67) (p=0.0077). The BF-ADL scores improved from baseline to 1 month by 2.4 points in the treatment arm (p=0.0006), whereas no significant improvements were observed in the SOC arm (p=0.55). While this study is promising, distal endpoints are needed to establish durability of the intervention. The contributory effects of medication therapies used during the study on the tremor power measurements is unknown.

Saimee (2025) reported the results of a randomized, double-blind, sham-controlled RCT from Iran investigating the safety and efficacy of a single, 40-minute transcutaneous peripheral nerve stimulation (TPNS) session on ET using a wristband device not available in the U.S, Pishgaman Rah Salamat Pars. The device applied stimulation to the median nerve and the superficial radial nerve, with a single counter-electrode on the posterior surface. A total of 88 participants were assigned to active TAPS stimulation (n=45) or sham procedure (n=43). Objective evaluations were taken with accelerometer-base tremor amplitude, Tremor Research Group’s Essential Tremor Rating Assessment Scale (TETRAS), the Bain and Findley Activities of Daily Living (BF-ADL), and CGI-I at baseline and 30, 60, and 90 minutes after cessation of treatment. Objective self-measures with CGI-I and BF-ADL were taken at 3, 4, 5, 6, and 24 hours after treatment. Both groups experienced significant improvement in tremor amplitude, but the control group only at 30 minutes, while the TAPS group reported improvements for all time points (p<0.001 for all). Similarly, both groups experienced significant improvement in TETRAS and BF-ADL measures, but no significant differences between groups were detected. On the CGI-I, only the control group demonstrated significant improvements, ad only during the first 90 minutes post-treatment (p=0.02). The results of this study indicate that TAPS resulted in a short-duration decrease in tremor amplitude following treatment, with no other benefits noted. Interpretation of these results is limited due to the use of a device not available in the US, as well as the single-treatment protocol and short follow-up period.

Ondo (2025) described the results of a double-blind, sham controlled RCT involving 125 participants with ET treated with either TPNS via the Felix^™ NeuroAI^™ Wristband (Fasikl, Inc. Bloomington, Minnesota) or sham treatment. A total of 83 participants were randomized to active TAPS while 42 received sham treatment. Participants wore their assigned device continuously for 90 days, with measures taken at baseline, 14, 30, 60, and 90 days. A total of 92 (78.4%) participants, 62 (75%) in the TPNS group and 36 (86%) in the control group were included in the 90 day analysis. All 125 study participants were included in the intent to treat analysis. At 90 days, the modified Activities of Daily Living (mADL) subscale of TETRAS results decreased by 6.9 points in the TPNS group (29.9 at baseline to 22.7) and by 2.7 points in the sham group (29.5 to 27.0), with significant difference between groups (p<0.001). Similar findings were reported when the data was analyzed for specific subgroups, including older vs younger age, sex, tremor severity, family history of tremor, current use of ET medications, and prior use of ET medications (p<0.05 for all). Additionally, at 90 days, the secondary outcome, reduction in mADL score 20% or greater, was reported in 61.3% participants in the TPNS group compared to 25.0% participants in the sham group (p<0.001). The authors reported that the change in mADL score over time in the 2 groups began to diverge at 14 days post-initiation of treatment. No significant between-group differences were reported with regard to improvements in the TETRAS performance subscale. Improvement on the CGI-I was seen in 69.4% participants  treated with TPNS compared to 44.4% participants in the sham group (p=0.02). On the PGI-I, 68% of the TPNS group and 50% on the sham group (50%) indicated improvement (p=0 .04). The authors noted that both the CGI-S and PGI-S numerically, but not significantly, favored the TPNS group (CGI-S, p=0.17 and PGI-S, p=0.17). When the QUEST activity (work and finances, hobbies and leisure, physical) and psychosocial scores were combined, the TPNS group showed significantly more improvement than the sham group (mean [SD] change of 6.6  vs. 2.6; p=0.04), more than the minimal clinically important improvement of 4.5. However, when the communication (voice) section was added, the total QUEST lost significance. No serious adverse device-related events were reported. However, mild skin irritation occurred in 28.9% of TPNS group participants and none in the sham group. The authors concluded that the use of the Felix NeuroAI TPNS device resulted in significant ET symptom improvement for up to 90 days. The results of this trial are promising, but limited by the significant loss to follow-up in the TPNS group, short follow-up and insufficient power to determine the validity of the secondary outcome metrics.

In 2026, Isaacson reported on a retrospective, ad hoc study of dada from the PROSPECT trial (FDA, 2017). This study evaluated underlying tremor improvement, measured using baseline tremor assessments compared to pre-stimulation assessments at prespecified trial visits, conducted after a washout period following the last stimulation session. The primary outcome measure was the responder rate for underlying tremor improvement was defined as the percentage of participants improving at least one point on any individual task on either the TETRAS or the BF-ADL tools. Data was available for 192 participants. The authors reported significant improvements in BL-ADL by 2.0 points at one month and 2.7 points at three months compared to baseline (p<0.001 for both). Similarly, TETRAS also showed significant improvements of 0.8 and 0.7 points at one and three months, respectively (p<0.001 for both). The responder analysis showed that over 80% of participants had underlying tremor improvement compared to baseline at both the 1-month and 3-month visits based on BF-ADL (p<0.001) and TETRAS (p<0.001). Additionally, based on BF-ADL data, at one month, 76.6% of participants “had at least one task shift from a functionally-impaired state (i.e., Severe/Moderate, score of 3 to 4)” at baseline to a “functionally-able state (i.e., Mild/No tremor, score of 1 to 2)”. That number increased to 81.2% at three months. The also reported that over 90% of participants had acute or lasting improvement in tremor severity, as measured by poststimulation BF-ADL and TETRAS, as previously reported (p<0.001 for both). It should be noted that the study limitations noted above still apply, including lack of blinding, absence of a control group (or randomization), and a short duration of follow-up.

In conclusion, the available evidence in peer-reviewed medical literature is insufficient to evaluate the effect of wrist-worn external TPNS or TAPS therapy on health-related outcomes in individuals with ET or any other condition. Additional evidence in the form of well-designed and conducted studies measuring longer follow-up times are needed to evaluate the clinical utility of this treatment approach.

According to the National Organization for Rare Disorders (NORD) rare disease database for essential tremor, nearly 7 million Americans are currently diagnosed with ET. The incidence of ET increases with age and more than 4% of individuals over age 40 have ET (NORD, 2022). The National Institute of Neurological Disorders and Stroke (NINDS) considers ET a chronic, progressive, and disabling neurological disease that causes uncontrolled rhythmic shaking. It is characterized by the presence of an action tremor (shaking during voluntary muscle movements), most often the hands or arms. In individuals with ET, other motor symptoms may be present including an unsteady manner of walking due to an inability to coordinate voluntary movements (ataxia), and in some cases, a variety of non-motor symptoms including cognitive impairment, depression or anxiety may develop. Population-based studies in the U.S. estimate that 2.2% of the U.S. population suffers from ET, and although most common among the elderly, the prevalence is increasing across age groups. Individuals with ET have higher rates of anxiety and depression than the general population, and difficulties with normal daily activities can potentially dramatically impact quality of life (NINDS, 2022).

There is no cure for ET and only a handful of pharmacologic or surgical treatments exist to help individuals manage their symptoms. First-line treatment consists of pharmacotherapies, such as propranolol and primidone. Second and third-line pharmacological approaches include topiramate, gabapentin, other beta-blockers, or benzodiazepines. However, response to pharmacotherapies varies, and high doses are often required for effective tremor reduction, increasing the burden of side effects for individuals and reducing tolerability and compliance. Deep brain stimulation surgery and magnetic resonance imaging (MRI)-guided focused ultrasound ablation are additional treatment options for tremor. However, not all individuals are appropriate candidates for such surgical procedures.

Electrical stimulation of peripheral nerves of upper limbs affected by tremors has been proposed as a treatment to decrease symptoms and improve function and quality of life. Currently two forms of stimulation have been proposed, transcutaneous peripheral nerve stimulation (TPNS) and transcutaneous afferent patterned stimulation (TAPS). TPNS involves the continuous delivery of electrical stimulation to targeted nerves and TAPS delivers periodic, patterned cyclic stimulation to the target nerves. Both approaches involve devices that work on the wrist like a watch or bracelet that deliver the electrical signal.

The FDA has cleared several wrist-worn devices for the treatment of ET, including the Cala Trio, the Cala kIQ, which deliver TAPS, and the Felix NeuroAI, which is a TPNS device. These devices are electronic wristband like devices with electrodes placed at specific points to activate targeted nerves.

Essential tremor (ET): A chronic, incurable condition with unknown cause characterized by involuntary, rhythmic movement of a body part, most typically the hands and arms.

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Peer Reviewed Publications:

1. Barath AS, Rusheen AE, Min HK, et al. Brain metabolic changes with longitudinal transcutaneous afferent patterned stimulation in essential tremor subjects. Tremor Other Hyperkin Mov. 2020; 10(1):52.
2. Brillman S, Colletta K, Borucki S, et al. Real-world evidence of transcutaneous afferent patterned stimulation for essential tremor. Tremor and Other Hyperkin Mov. 2022; 12:1-11.
3. Castrillo-Fraile V, Peña EC, Gabriel Y Galán JMT, et al. Tremor control devices for essential tremor: a systematic literature review. Tremor Other Hyperkinet Mov (N Y). 2019 Dec 5;9.
4. Dai D, Fernandes J, Kim H, et al. Comparative effectiveness of transcutaneous afferent patterned stimulation therapy for essential tremor: a randomized pragmatic clinical trial. Tremor and Other Hyperkin Mov. 2023;16 (13):38.
5. Isaacson SH, Peckham E, Tse W, et al. Prospective home-use study on non-invasive neuromodulation therapy for essential tremor. Tremor Other Hyperkin Mov. 2020; 10:1-16.
6. Isaacson SH, Peckham E, Tse W, et al. Underlying tremor improvement with consistent use of transcutaneous afferent patterned stimulation in patients with essential tremor. Tremor Other Hyperkinet Mov (N Y). 2026; 16:1.
7. Isaacson S, Pahwa R, Brillman S, et al. Clinical benefit of transcutaneous afferent patterned stimulation (TAPS) in essential tremor patients with high unmet need: a secondary analysis of TAPS studies, Expert Rev Med Devices. 2023; 20(12):1211-1218.
8. Lin PT, Ross EK, Chidester, et al. Non-invasive neuromodulation in essential tremor demonstrates relief in a sham-controlled pilot trial. Mov Disord. 2018; 33:1182-1183.
9. Lu C, Khosla D, Kent A, et al. Transcutaneous afferent patterned stimulation for essential tremor: real-world evidence with long term follow-up. Tremor and Other Hyperkin Mov. 2023;13:1-13.
10. Ondo WG, Lv W, Zhu X, et al. Transcutaneous peripheral nerve stimulation for essential tremor: a randomized clinical trial. JAMA Neurol. 2025; 82(12):1235-1242.
11. Pahwa R, Dhall R, Ostrem J, et al. An acute randomized controlled trial of noninvasive peripheral nerve stimulation in essential tremor. Neuromodulation. 2019; 22:537-545.
12. Yu JY, Rajagopal A, Syrkin-Nikolau J, et al. Transcutaneous afferent patterned stimulation (TAPS) therapy reduces hand tremor for one hour in essential tremor patients. Front. Neurosci. 2020; 14:530300.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Cala Health, Inc. A Pilot Study of the Cala ONE device for essential tremor. NLM Identifier: NCT03152136. Last updated April 30, 2019. Available at: https://clinicaltrials.gov/study/NCT03152136. Accessed on May 5, 2026.
2. Cala Health, Inc. Cala ONE Device for Essential Tremor. NLM Identifier: NCT02629614. Updated July 18, 2023. Available at: https://clinicaltrials.gov/study/NCT02629614. Accessed on May 5, 2026.
3. Cala Health, Inc. Long-Term Transcutaneous Stimulation and Essential Tremor: A PET Study. NLM Identifier: NCT03778060. Updated January 30, 2026. Available at: https://clinicaltrials.gov/study/NCT03778060. Accessed on May 5, 2026.
4. Cala Health, Inc. Prospective Study for Symptomatic Relief of ET with Cala Therapy (PROSPECT). NLM Identifier: NCT03597100. Updated October 12, 2023. Available at: https://clinicaltrials.gov/ct2/show/NCT03597100. Accessed on May 5, 2026.
5. Cala Health, Inc. RWE Study Utilizing the Cala Trio Device in Patients With Essential Tremor. NLM Identifier: NCT05540626. Last updated May 7, 2025. Available at: https://clinicaltrials.gov/study/NCT05540626. Accessed on May 5, 2026.
6. Cala Health, Inc. Symptomatic Relief of Action Tremor With Cala Trio Using Trio+ Bands. NLM Identifier: NCT05480215. Updated July 29, 2022. Available at: https://clinicaltrials.gov/study/NCT05480215. Accessed on May 5, 2026.
7. Cala Health, Inc. Transcutaneous Afferent Patterned Stimulation (TAPS) for Reduction of Parkinson's Disease (PD) Related Action Tremor. NLM Identifier: NCT05012579. Updated February 13, 2024. Available at: https://clinicaltrials.gov/study/NCT05012579. Accessed on May 5, 2026.
8. Centers for Medicare and Medicaid Services (CMS). National Coverage Determination: Treatment of motor function disorders with electric nerve stimulation. NCD#160.2. Effective April 1, 2003. Available at: https://www.cms.gov/medicare-coverage-database/view/ncd.aspx?ncdid=22&ncdver=2&keyword=essential%20tremor&keywordType=starts&areaId=all&docType=NCD,F&contractOption=all&sortBy=relevance&bc=1. Accessed on May 5, 2026.
9. International Essential Tremor Foundation Consensus and Physician Experts. Essential tremor in adult patients. 2021. Updated April 7, 2026. Available at: https://www.guidelinecentral.com/guideline/502775/. Accessed on May 5, 2026.
10. U.S Food and Drug Administration (FDA). 510k Summary. K2032088. Cala Health, Inc. Cala Trio. Available at: https://www.accessdata.fda.gov/cdrh_docs/pdf20/K203288.pdf. Accessed on May 5, 2026.
11. U.S Food and Drug Administration (FDA). 510k Summary. K222237. Cala Health, Inc. Cala kIQ. Available at: https://www.accessdata.fda.gov/cdrh_docs/pdf22/K222237.pdf. Accessed on May 5, 2026.
12. U.S Food and Drug Administration (FDA). 510k Summary. K250096. Fasikl Inc. Felix NeuroAI System. Available at: https://www.accessdata.fda.gov/cdrh_docs/pdf25/K250096.pdf. Accessed on May 5, 2026.
13. Zesiewicz TA, Elble RJ, Louis ED, et al. Evidence-based guideline update: Treatment of essential tremor. Report of the Quality Standards Subcommittee of the American Academy of Neurology. Reaffirmed on July, 19, 2025. Available at: https://www.aan.com/Guidelines/home/GuidelineDetail/492. Accessed on May 5, 2026.

1. National Institute of Neurological Disorders and Stroke. Tremor fact sheet. Last reviewed March 13, 2026. Available at: https://www.ninds.nih.gov/health-information/disorders/essential-tremor?search-term=essential%20tremor%20fact%20sheet. Accessed on May 5, 2026.
2. National Library of Medicine. Medical Encyclopedia. Essential tremor. Review date June 13, 2024. Available at: https://medlineplus.gov/ency/article/000762.htm#:~:text=Essential%20tremor%20(ET)%20is%20a,stop%20the%20shaking%20at%20will. Accessed on May 5, 2026.
3. National Library of Medicine. Journal list. Ondo W, Hashem V, LeWitt PA, et al. Comparison of the Fahn-Tolosa-Marin Clinical Rating Scale and the Essential Tremor Rating Assessment Scale. Mov Disord Clin Pract. 2017: 23;5(1):60-65. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174461/. Accessed on May 5, 2026.
4. National Organization for Rare Disorders. Rare disease database. Essential tremor. Available at: https://rarediseases.org/?s=essential+tremor&rdb-search=true&post_type%5B%5D=rare-diseases&post_type%5B%5D=gard-rare-disease. Accessed on May 5, 2026.

Cala kIQ
Cala Trio
Felix NeuroAI Wristband
External upper limb tremor stimulator
Transcutaneous afferent patterned stimulation (TAPS)

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.

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