MDS Staff Liaison: Maggie Calenberg
The Tremor Study Group (TSG) evolved from the Task Force on Tremor, which completed its work in June 2017. The Task Force reviewed published rating scales1 and transducers2 for measuring tremor and developed a revised classification scheme for tremor.3 An evidence-based review of published treatments for essential tremor was conducted.4 Based on this work, the following objectives for the TSG were identified.
1. Deep tremor phenotyping
A systematic, deep phenotyping of patients with monosymptomatic tremor disorders (e.g., essential tremor) is needed. The TSG is therefore developing an ordinal assessment tool that will guide clinicians in deep tremor phenotyping, so as to distinguish essential tremor from essential tremor plus and other forms of tremor that are commonly mistaken as essential tremor. The assessment tool will capture subtle or questionable features of dystonia, myoclonus, parkinsonism and ataxia. A video protocol is being developed in conjunction with this tool. To validate this assessment and video protocol, each member of the TSG will produce a video assessment of three patients: essential tremor, essential tremor plus and a combined tremor syndrome that presented with the sole complaint of tremor (monosymptomatic tremor disorder). The ultimate goal is to incorporate this assessment tool and video protocol into a web-based REDCap database that can be used in conjunction with clinical research studies.
2. Tremor scales development
Othostatic tremor severity scale
In our previous review of available tremor assessment scales, it was found that there is no validated scale for orthostatic tremor.1 Treatment of this relatively rare condition is being approached pharmacologically and surgically, and a validated scale for orthostatic tremor has been developed.5
Unified Tremor Rating Scale
A scale is needed that captures typical (action tremor) and atypical (e.g., rest tremor, prominent lower limb tremor) tremor in patients with essential tremor and essential tremor plus. We are developing a new scale that builds upon the strengths of the Fahn-Tolosa-Marín scale and the Essential Tremor Rating Assessment Scale (TETRAS). This scale will become one of a battery of scales for the clinical assessment of tremor.
3. Instrumented measures of tremor
Certain aspects of tremor are believed to be useful in distinguishing essential tremor from other tremors (e.g., dystonic tremor and rhythmic cortical myoclonus). However, these tremor characteristics (e.g., irregularity in amplitude and rhythm, fluctuating axis of rotation, posturing of the head or limb) are very difficult to assess by clinical inspection. We believe there is a role for motion transducers, computerized video analysis, and other electrophysiologic methods in the characterization of tremor. We envision such methods being used in a deep phenotyping of tremor patients.
4. Web-based tremor database
The TSG has the overall goal of promoting greater depth and standardization in the phenotyping of patients with tremor disorders, particularly monosymptomatic tremor disorders such as essential tremor. The scales developed by the TSG will be incorporated into a web-based tremor database that will have data elements in common with the Dystonia Coalition database. This database will be linked to an archive of patient videos and to repositories of DNA samples for research.
5. DBS tolerance study
Alfonso Fasano and Rick Helmich are leading a study of tolerance in patients treated with deep brain stimulation for tremor. Clinical phenotype, electrode location, and electrophysiologic markers are being examined as possible predictors of treatment outcome.
The TSG is comprised of those members of the original Task Force who agreed to participate in one or more of the above projects. Additional members have been added through their participation in an ongoing project. Persons interested in membership should contact one of the TSG chairs by email with attached CV and brief statement of purpose. Applicants for membership must be members of IPDMS. New members must participate in an ongoing project or propose to spearhead a new project. Bylaws for the TSG have been developed.
1. Elble R, Bain P, Forjaz MJ, et al. Task force report: scales for screening and evaluating tremor: critique and recommendations. Mov Disord 2013;28(13):1793-1800.
2. Haubenberger D, Abbruzzese G, Bain PG, et al. Transducer-based evaluation of tremor. Mov Disord 2016;31(9):1327-1336.
3. Bhatia KP, Bain P, Bajaj N, et al. Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord 2018;33(1):75-87.
4. Ferreira JJ, Mestre TA, Lyons KE, Benito-Leon J, Tan EK, Abbruzzese G, et al. MDS evidence-based review of treatments for essential tremor. Mov Disord 2019;34:950-8.
5. Merola A, Torres-Russotto DR, Stebbins GT, Vizcarra JA, Shukla AW, Hassan A, et al. Development and Validation of the Orthostatic Tremor Severity and Disability Scale (OT-10). Mov Disord 2020;35:1796-801.