Clinical outcome assessments (COA) are essential for evaluating symptom severity, treatment response, and disease progression in movement disorders. The Movement Disorder Society (MDS) has long supported the review, validation, and recommendation of COAs through its COA program, and regular reevaluation is crucial as clinical knowledge and treatments evolve. This review evaluates current COA recommendations across ataxia, Huntington's disease (HD), dystonia, tremor, tics, progressive supranuclear palsy (PSP), restless legs syndrome (RLS), and drug‐induced movement disorders (DIMD).
It (1) summarizes existing recommended COAs, (2) reviews new evidence per construct, and (3) highlights areas needing revision, to inform clinical practice, research, and future resource allocation.
Patients and Methods
The Scientific Evaluation Committee (SEC) of the MDS‐COA program commissioned a position paper on the current state of COA recommendations. The review followed a 2‐step process as follows:
Step 1: Review of the MDS Database of Publications of COA Appraisal in Movement Disorders Other Than Parkinson's Disease
A focused literature search of the database of publications on COA critiques and recommendations (https://www.movementdisorders.org/MDS/MDS‐Rating‐Scales/Rating‐Scales‐Criti.org‐and‐Recommendations.htm) was conducted in March 2024. Using a standardized template, 2 independent reviewers identified the constructs and extracted relevant data from COAs that were recommended, suggested, or listed based on the established MDS‐COA program criteria.1 Discrepancies were discussed at consensus meetings and resolved by agreement between the reviewers.
Step 2: Scoping Review
A scoping review was conducted for each construct to identify new COAs or updated clinimetric data. Searches were performed in PubMed and Web of Science databases. PubMed was selected for its coverage of the biomedical and clinical literature, and Web of Science for complementary multidisciplinary coverage, including journals outside clinical neurology, in which digital and wearable outcome measures are reported.
Relevant review articles identified through the searches were additionally examined for eligible primary studies. The search algorithm used combinations of the following terms: disease or disorder name, scale‐related terms (eg, rating scale, questionnaire, clinical outcome assessment), and psychometric terms (eg, validation, reliability, validity, responsiveness, sensitivity to change) (details in Table SS1). For each construct, the search covered publications from January 1 of the year of publication of the corresponding MDS review through May 3, 2026.
Studies involving adults or children, regardless of study design that used COAs to assess symptoms in a specific movement disorder, were included. No language restriction was applied at the search stage. Records published in languages other than English were screened using the English‐language title and abstract provided by the indexing database and were retained where these established eligibility and reported the relevant clinimetric data.
Formal translation of full texts was not undertaken. Relevant publications were imported into the Rayyan2 application for screening. Each construct was allocated to 1 reviewer.
Across all constructs, the same predefined eligibility criteria were applied; records for which eligibility was uncertain were referred to a second reviewer and, where uncertainty persisted, discussed within the writing group; and the final set of included studies for each construct was verified by the coordinating authors and reviewed by the SEC prior to synthesis. The literature search and study selection process results are illustrated in a Preferred Reporting Items for Systematic reviews and Meta‐Analyses (PRISMA) flow diagram.3
Consistent with the evidence‐mapping purpose of this scoping review, methodological quality assessment of individual studies was not performed.4, 5
Step 3: Summary of Updated COA Overview
The updated overview of existing MDS‐recommended COAs is described by movement disorder and construct in a predefined narrative structure (construct, current state, gaps identified, new evidence, conclusions and future directions). The decision to recommend an updated review for each construct was based not on the volume of new publications alone but on a judgment of whether accumulated evidence—new instruments, validation data, or replication studies—is likely to alter existing MDS recommendation levels, from listed to suggested or suggested to recommended.
COA abbreviations are listed in Table SS2.
Results
The 13 constructs identified in step 1 yielded 2220 studies in step 2. After duplicates were removed, 1777 studies were screened. A full‐text review excluded 616 studies that did not meet the eligibility criteria, resulting in the inclusion of 261 studies (Fig.
SS1). Constructs are presented by disease entity (ataxia, HD, dystonia, PSP, RLS, DIMDs) and, where applicable, by symptom domain (behavior, cognition, motor, quality of life [QoL]).
Construct: Ataxia
Current State
In 2021, an MDS Task Force reviewed 14 COAs for ataxia—9 clinician‐rated scales and 5 functional tests—concluding that no single tool is suitable across all ataxia populations and that instrument selection should be disease specific6 (Table 1).
Gaps Identified
Major limitations include poor applicability to severely affected and pediatric populations, as well as ceiling and floor effects. The Ataxia Global Initiative Working Group highlighted priorities: optimizing the Scale for the Assessment and Rating of Ataxia (SARA), expanding patient‐reported outcomes (PRO), improving sensitivity to change, and defining clinically meaningful change thresholds.7
New Evidence
SARA remains the most widely used COA, translated into multiple languages8, 9, 10, 11 and applied across lysosomal disorders,12 autosomal recessive spastic ataxia of Charlevoix‐Saguenay (ARSACS),13 stroke,14 multiple sclerosis,11 ultrarare autosomal recessive cerebellar ataxias,15 and pediatric populations, alone16 and in combination with the International Cooperative Ataxia Rating Scale (ICARS) domains.17 ICARS18 and BARS19 have similarly undergone linguistic validation.
Large natural history studies have shown variability in SARA responsiveness across disease stages, genotypes, and spinocerebellar ataxia (SCA) subtypes.20, 21, 22, 23 Rare disease‐specific scales support niche populations but remain disconnected from broader frameworks.24, 25 The modified (functional) Scale for the Assessment and Rating of Ataxia (f‐SARA) shows improved content validity and psychometric properties in SCAs,26, 27 though item‐level analyses indicate unequal contributions to sensitivity and no consensus on an optimized version.22
Several composite tools have emerged: Spastic Ataxia Composite (SPAXCOM), combining SARA, SPRS, and Friedreich's Ataxia Rating Scale (FARS)‐ADL (activities of daily living), showed improved 2‐year sensitivity but lacked external validation28; SCACOMS, integrating CGI‐I, FARS functional staging, and f‐SARA, demonstrated sensitivity in early SCAs and may outperform single scales,29 with patient‐perspective analyses broadly supportive despite item‐weighting limitations.30, 31 FXTAS‐RS and PRAIS are in early validation with no independent replication.32, 33
PRO development has accelerated: Patient‐Reported Outcome Measure (PROM)‐Ataxia has undergone longitudinal validation in SCAs, demonstrating sensitivity to progression,34 and has been translated into Chinese, Italian, and Brazilian Portuguese,35, 36, 37 though most lack longitudinal or treatment‐sensitivity evaluation. PRAIS and FACR‐HI introduce conceptual fragmentation without consensus on a preferred endpoint.38
Functional assessments remain under‐integrated: FARS‐ADL exhibits strong psychometric and content validity in SCA1 and SCA3,39, 40 whereas DGI and ARAT are applied inconsistently.41, 42 In Friedreich ataxia, mFARS endpoints have gained traction in clinical trials and regulatory contexts, supported by established test–retest reliability of FARS,43 demonstrating construct validity, sensitivity to change, and minimal important change for FARS‐ADL across multiple subtypes,44 and discriminative validity of digital gait measures against healthy controls.45 Efforts to harmonize SARA, mFARS, and ICARS scores in Friedreich ataxia have yielded interconversion formulas enabling cross‐study and meta‐analytic comparisons, though axial subscores show scale‐dependent sensitivity at different disease stages.46 Together, these data represent a strengthened psychometric foundation for FARS‐based instruments, with early harmonization work between FARS‐based and SARA/ICARS scoring offering a model for similar efforts across other ataxia subtypes.
Remote assessment has expanded: SARAhome exhibited strong correlation with in‐person scoring but also intraindividual variability,47 confirmed across multiple time points in a multicenter SCA3 study.48 Additional platforms enable real‐time video‐based evaluation,49, 50 including in Friedreich ataxia51; early comparability has been shown in other populations such as multiple sclerosis,52 and ARSACS,53, 54 though equivalence to in‐person assessment and generalizability remain uncertain. Emerging instruments address previously underrepresented nonmotor domains, including Scale for Ocular Motor Disorders in Ataxia (SODA),55 the Cerebellar Impulsivity‐Compulsivity Scale,56 and the modified INAS, applied longitudinally in Friedreich ataxia over 12 years to characterize non‐ataxia features beyond cerebellar symptoms57; these tools are not yet integrated into standard assessment batteries, and the Cerebellar Cognitive Affective Syndrome Scale remains excluded as it does not directly measure ataxia symptoms.58 Wearable sensors, smartphone‐based tools, and machine‐learning models show promise for gait analysis, kinematic measures, and digital biomarkers across Friedreich ataxia, ARSACS, and SCAs, including a prospective composite digital balance score,45, 59, 60, 61, 62, 63, 64, 65 and feasible real‐world monitoring via smartphone apps66 and wearable tools such as Q‐Motor67 though most studies remain exploratory with small samples and limited validation.
A minimal clinically important difference (MCID) for SARA of ~1.5 points has been established using combined anchor‐ and distribution‐based methods,68 representing an important advance for trial interpretation.
Conclusion and Future Directions
Despite substantial progress, most newly developed composite scales, PROs, and digital tools lack independent replication, longitudinal validation, and standardization, conditions that should be met before a formal updated review can meaningfully revise existing recommendations. The most productive next step is therefore consensus work to harmonize existing instruments and establish validation standards, including better tools for pediatric and severely affected populations. An updated review is not warranted.
Construct: Behavioral Symptoms in HD
Current State
The 2016 MDS review evaluated 27 behavioral COAs across 7 domains in HD, recommending only 3 scales, the Irritability Scale, the Beck Depression Inventory‐II (BDI‐II), and the Hospital Anxiety and Depression Scale (HADS), and exclusively for screening (Table 2). No instrument was recommended for diagnosis, severity grading, longitudinal tracking, or treatment response.69
Gaps Identified
The primary unmet need is for HD‐specific, multidomain, stage‐sensitive instruments capable of reliably capturing severity and longitudinal change, with adequate attention to disease‐related anosognosia limiting self‐report accuracy.
New Evidence
The Movement Disorders Interpretation Bias Scale (MDIB) measures negative interpretation bias linked to anxiety in HD, representing a conceptual advance, though validation remains preliminary.70 The short Lille Apathy Rating Scale (LARS‐s) has received partial psychometric support for profiling apathy subdomains but is not yet trial ready.71 Quality of Life in Neurological Disorders (Neuro‐QoL) and Patient‐Reported Outcomes Measurement Information System (PROMIS) mental health PROs represent the most significant advance since 2016, demonstrating good reliability, test–retest stability, and responsiveness over 12 to 24 months72, 73; anosognosia74 remains a key limitation requiring companion or clinician input alongside self‐report. The Huntington's Disease Behavioral Questionnaire (HD‐BQ) shows strong initial psychometric properties,75 with 2026 companion‐report data indicating utility for mitigating anosognosia‐related underreporting.76 The Problem Behaviours Assessment–short (PBA‐s) has been validated in Spanish with good inter‐ and intra‐rater reliability,77 though large‐scale clinimetric work suggests limited sensitivity to early or mild behavioral change.78 Factor‐analytic work on the SIS in HD remains insufficient for routine use.79
Conclusions and Future Needs
Behavioral assessment in HD has expanded, but substantial gaps persist: limited independent validation, insufficient early‐stage sensitivity, persistent anosognosia challenges, and incomplete evidence of treatment sensitivity. Future work should prioritize external validation, companion‐ or clinician‐reported input, and multidomain HD‐specific tools suitable for clinical trials. An updated review is not required currently.
Construct: Cognition in HD
Current State
The 2017 MDS review found no cognitive COA meeting criteria for “recommended” status in HD; Montreal Cognitive Assessment (MoCA) was “recommended with caveats” for severity assessment and “suggested” for screening (Table 2).80
Gaps Identified
Key unmet needs include insufficient HD‐specific clinimetric validation, scarce longitudinal and treatment‐sensitivity data, and limited cross‐cultural evidence. No objective scale demonstrated adequate sensitivity for disease stage or trial readiness.
New Evidence
Among established global screeners, MoCA has received Italian validation,81 the Chinese Unified Huntington's Disease Rating Scale (UHDRS) demonstrated adequate reliability,82 and factor analysis questioned the standard Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) domain structure in HD.83 Parkinson's Disease–Cognitive Rating Scale (PD‐CRS) has exhibited validity and reliability for global cognition with established HD‐related mild cognitive impairment and HD dementia cutoffs,84 and has demonstrated stage‐differentiated cognitive trajectories in a 2023 comparison study,85 positioning it as a leading candidate for future upgrading, though evidence remains largely from 1 group. Edinburgh Cognitive and Behavioural ALS Screen (ECAS) shows promise given its reduced motor demands but requires further HD‐specific replication.86
Among novel paradigms, the Maze task demonstrates high 12‐month sensitivity to change, outperforming established progression measures but remaining experimental87; LASSI‐L detects early deficits in premanifest HD with limited external replication.88 Among digital tools, SelfCog is the most mature, with multilingual validity against classical tests and imaging markers and 1‐year decline detection,89 whereas HD‐Mobile90 and DAT91 remain at early validation stages. HD‐CFRS provides a validated assessment of functional cognitive consequences in symptomatic HD,92 and Neuro‐QoL Cognition demonstrates longitudinal sensitivity suitable for PRO trial endpoints.93, 94 Huntington's Disease Everyday Functioning scale (Hi‐DEF) captures early functional cognitive impact across multiple psychometric studies.95, 96, 97 Huntington's Disease Cognitive Assessment Battery (HD‐CAB) has growing support as a fit‐for‐purpose trial battery.98
Conclusions and Future Needs
Key gaps include limited independent replication, sparse cross‐cultural and longitudinal validation, absent MCID estimates, and insufficient early‐stage sensitivity. The most defensible interim strategy combines a brief objective cognitive measure with a functional or PRO outcome to capture real‐world relevance and mitigate anosognosia. Although PD‐CRS and select digital tools show promise, evidence remains too preliminary or insufficiently replicated to support a formal updated review at this time.
Construct: Motor Symptoms in HD
Current State
A 2018 MDS review of functional ability measures in HD recommended the Tinetti Mobility Test, Berg Balance Scale, and Six‐Minute Walk Test (Table 2); no functional rating scale met recommendation criteria.99
Gaps Identified
Key limitations included insufficient longitudinal validation, absence of validated upper‐limb measures, and ceiling effects in early and premanifest HD.
New Evidence
Clinician‐rated and composite scales: cross‐cultural validation of the Unified Huntington's Disease Rating Scale–Total Motor Score (UHDRS‐TMS) has confirmed reliability in non‐Western populations,82 and inter‐rater reliability analyses show improved overall agreement,100 though challenges persist for dystonia subitems and construct validity remains incomplete. Composite and modified scales have been proposed to improve stage sensitivity, including the composite UHDRS101 and juvenile‐onset adaptations.102
Upper‐limb and functional task assessments: upper‐limb task assessments, including shirt buttoning,103 Clinch Token Transfer Test,104 Upper Limb Token Transfer Test,105 and isometric force assessment,106 lack robust longitudinal validation. WHODAS 2.0 (World Health Organization Disability Assessment Schedule 2.0) has been validated in a Polish HD cohort as a general disability measure.107 Dual‐task paradigms108 and the Step Test Evaluation of Performance on Stairs (STEPS)109 offer ecologically valid motor assessment but are not integrated into standard batteries. The Brief Fall Questionnaire for Huntington's Disease (FALL‐HD) has been developed and validated for fall screening in HD.110
Digital and technology‐based measures: the HD Digital Motor Score leverages smartphone‐based assessment of gait, balance, chorea, and tapping speed, offering improved sensitivity to change, though validation remains insufficient for regulatory use.111 Speech measures are emerging as both patient‐relevant outcomes112 and objective digital biomarkers of premanifest HD progression,113 though standardization and longitudinal validation remain incomplete.
Conclusion and Future Needs
Despite the expansion of tools, key challenges persist: absence of a validated early motor biomarker, insufficient validation of upper‐limb and digital assessments, and poor integration of motor, functional, and real‐world outcomes. Future research should prioritize harmonization, longitudinal validation, and multidomain integration to support clinical trials in early and prodromal HD. An updated review is not yet warranted, though digital motor scoring approaches should be prioritized for systematic appraisal as supporting evidence matures.
Construct: Quality of Life in HD
Current State
The 2018 MDS review found the 36‐Item Short Form Health Survey (SF‐36) as the only recommended patient‐reported QoL instrument; no tool was recommended for caregivers.114
Gaps Identified
Key concerns included self‐report validity given impaired insight, insufficient clinimetric evidence for several instruments, uneven representation across disease stages, predominantly cross‐sectional data, and underdeveloped caregiver outcomes.
New Evidence
HD‐specific QoL instruments have gained further clinimetric evidence: Huntington's Disease Quality of Life Questionnaire (HD‐QoL) has been validated across severity stages across physical‐functional, cognitive, mood, and worry domains115; Huntington's Disease Health‐Related Quality of Life (HDQLIFE) provides broader HD‐specific health‐related QoL coverage, including late‐stage and end‐of‐life planning116; and Huntington's Disease Patient‐Reported Outcome–Triad (HD‐PRO‐TRIAD) demonstrated strong reliability and construct validity.117 However, the field now includes multiple partially overlapping instruments with limited head‐to‐head comparisons, uncertain harmonization, and incomplete responsiveness data. The Huntington's Disease Health Index (HD‐HI) offers patient‐centered symptom burden assessment with preliminary validity data but limited stage‐specific performance evidence.118 The Social Relationships Self‐Report Questionnaire (SRSQ) associates perceived social relationships with motor, cognitive, and functional decline, though validation is limited to a single population.119 Neuro‐QoL has demonstrated acceptable reliability and responsiveness across physical, mental, and social domains,120, 121, 122, 123 though HD‐specific concerns, including genetic burden, stigma, and future uncertainty, remain insufficiently captured. The Huntington's Disease Quality of Life–Carers (HDQoL‐C) and its short form demonstrate strong cross‐cultural validity for caregiver QoL across multiple countries,124 though caregiver outcomes remain underrepresented in longitudinal and treatment‐focused research.
Conclusions and Future Needs
QoL measurement in HD has progressed substantially, but domains such as stigma, social participation, genetic burden, and future uncertainty remain underrepresented in commonly available instruments. Priorities include longitudinal validation, improved responsiveness data, caregiver outcome integration, and harmonization to support trial readiness. Because of the proliferation of partially overlapping instruments without head‐to‐head comparison, an updated review is not yet warranted until harmonization efforts clarify which HD‐specific measures should be prioritized.
Construct: Dystonia
Current State
In 2013, an MDS Task Force reviewed 36 COAs for dystonia, of which 28 met criteria for full evaluation and 7 achieved “recommended” status, all assessing motor severity (Table 3).125
Gaps Identified
Anatomical coverage is uneven, with trunk, lower‐limb, arm, and task‐specific dystonias lacking adequate tools. Nonmotor features, including sensory symptoms, pain, sleep, cognition, and psychiatric comorbidities, are insufficiently captured. No instrument supports diagnostic differentiation.
Pediatric tools are underdeveloped, and implementation barriers include limited training standards and scarcity of validated translations.
New Evidence
For blepharospasm, the blepharospasm severity scale has been developed126 and validated in a multicenter cohort127; the Craniocervical Dystonia Questionnaire‐24 (CDQ‐24) has been translated into Spanish,128 and video‐based rating has been explored.129 In a comparative study of hemifacial spasm, Tunc's scale was found to be superior for inter‐rater reliability.130 For laryngeal dystonia, strong patient–clinician concordance was demonstrated for the USDRS,131 the Communicative Participation Item Bank has been validated,132 a new Persian Adductor Laryngeal Dystonia–Vocal Symptoms Scale has been developed,133 and the Voice Disability Coping Questionnaire has been psychometrically evaluated.134 A screening tool for oromandibular dystonia has been introduced.135 For cervical dystonia, the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) has been further evaluated, including video‐based and avatar‐based versions136, 137, 138, 139, 140; CCDRS has been further validated141, 142; Cervical Dystonia Impact Profile‐58 (CDIP‐58) psychometric support has been expanded143; LIVECHART PRO has been published and exhibited good reliability144; and the Pain in Dystonia Scale (PIDS) has been developed,145 with subsequent Italian multicenter validation.146 For task‐specific dystonias, PROs for musicians'147 and embouchure148 dystonia have been developed. The Dystonia Non‐Motor Symptoms Questionnaire (DNMSQuest) has been developed,149 translated into German,150 and validated for nonmotor screening in generalized dystonia, including a multicenter craniocervical cohort,151, 152 supporting its utility across focal and generalized phenotypes, including cervical dystonia. DNMSQuest and CDIP‐58 are currently under separate evaluation as part of the MDS nonmotor COA program; findings from that initiative should inform any future dystonia‐specific review.
Balance confidence153 and video‐based severity ranking154 have also been explored. For pediatric dystonia, DIS and DIS‐II have been validated in inherited/idiopathic dystonia and dyskinetic cerebral palsy155, 156, 157; the Hypertonia Assessment Tool has been introduced and validated158, 159, 160; and the Movement Disorder‐Childhood Rating Scale (MD‐CRS), BAD, and age‐related considerations for the Burke‐Fahn‐Marsden have been evaluated.160, 161, 162 For X‐linked dystonia parkinsonism, dedicated COAs have been cross‐culturally validated,163, 164, 165 a differential diagnosis questionnaire has been developed,164 and a culturally adapted MoCA has been published.166
Conclusions and Future Directions
Given the breadth of new evidence spanning motor severity, nonmotor features, pediatric populations, task‐specific subtypes, and remote assessment methods, an updated review is warranted. Remaining priorities include harmonization, coverage of underrepresented phenotypes, pediatric tool development, and cross‐cultural validation.
Construct: Tremor
Current State
In 2013, an MDS Task Force reviewed 32 COAs for tremor screening and severity evaluation, of which 8 met criteria for “recommended” status (Table 4).167
Gaps Identified
No scale has been comprehensively evaluated for sensitivity to change, limiting confidence in detecting meaningful longitudinal or treatment‐related improvements. Test–retest reliability, minimal detectable change, and MCID remain insufficiently defined for most instruments. Inter‐rater reliability depends on rater training, yet training procedures lack standardization.
Additional gaps include floor and ceiling effects, limited assessment of non‐upper‐limb tremor, and scarce linguistic validation. The 2013 review focused predominantly on essential tremor; COA coverage for other tremor subtypes, including dystonic, cerebellar, orthostatic, and Holmes tremor, remains insufficient. Furthermore, the distinction between essential and dystonic tremor cannot be reliably resolved even by supervised machine learning, with classification accuracy as low as 29%,168 underscoring fundamental diagnostic challenges that outcome measures must contend with.
Finally, tremor severity cannot be adequately or interchangeably captured by any single assessment modality; clinician‐rated scales, PROs, performance‐based measures, and digital tools each reflect distinct aspects of tremor burden and are likely all required for comprehensive assessment.
New Evidence
TETRAS (The Essential Tremor Rating Assessment Scale)‐PRO has been developed as the first essential tremor‐specific PRO,169 followed by the Patient Attainment Scale‐Essential Tremor (PAS‐ET)170 and the Most Bothersome Symptom‐Essential Tremor Questionnaire (MBS‐ET),171 alongside new measures of tremor‐related stigma172 and enfeeblement.173 The Quality of Life in Essential Tremor Questionnaire (QUEST) has been validated in French, German, Hungarian, and Turkish174, 175, 176, 177; the Fahn–Tolosa–Marin scale in Spanish,178 including for patient self‐assessment179; and the Essential Tremor Embarrassment Assessment in French.174 Spiral‐drawing assessments have been validated as screening tools180, 181 and severity measures,182 and comparative harmonization studies of key tremor COAs have been undertaken.183, 184, 185 Wearable sensor‐based assessments show promise for objective tremor quantification,186, 187, 188, 189 remote smartphone‐ or tablet‐based tools demonstrate feasibility for screening and monitoring,190, 191, 192 and video‐based motion analysis has been evaluated as a quantitative tool during magnetic resonance–guided focused ultrasound surgery (MRgFUS) thalamotomy.193
Conclusions and Future Recommendations
New COAs and additional psychometric validation align with earlier MDS recommendations, but persistent gaps remain in sensitivity to change, standardized rater training, and clinical interpretability. Expanding therapeutic options, including growing use of MRgFUS, and insufficient COA coverage beyond essential tremor together make tremor the highest priority for an updated MDS review. Such a review should broaden scope to include dystonic, orthostatic, cerebellar, and other tremor disorders, and should address whether clinician‐rated scales, PROs, performance‐based measures, and digital tools are interchangeable or complementary in capturing tremor severity.
Construct: Tics
Current State
A 2017 MDS Task Force reviewed 16 severity scales and 13 screening instruments for tic disorders, recommending 5 severity scales (Yale Global Tic Severity Scale [YGTSS], TSCGI, TDS, STSSS, Premonitory Urge for Tics Scale [PUTS]) and 2 screening tools (Motor Tic, Obsessions and Compulsions, Vocal Tic Evaluation Survey [MOVES], A‐TAC).194 The YGTSS has since been adopted as the gold standard in European clinical guidelines.195
Gaps Identified
No single tool captures the full multidimensional nature of tic disorders, including frequency, intensity, complexity, premonitory urges, and functional impairment. Sensory phenomena, contextual variability, and psychosocial impact are inconsistently represented, and validation across age groups, cultures, and clinical settings remains limited.
New Evidence
A large‐scale psychometric evaluation confirmed the YGTSS's robustness, with separate reporting of severity and impairment scores preferred over a global composite.196 Revisions have been proposed,197 with validity supported in parent‐reported formats198 and multiple cultural settings.199 PUTS has been translated and validated in Korean, Chinese, and Spanish populations,200, 201, 202 with reliable use in individuals older than 10 years,203 though utility in younger children remains limited.204 The IPUTS was introduced to capture interindividual variability197 and has been validated in Chinese.205 MRVS provides a shorter practice‐oriented tool with good correlation to YGTSS.206 PTQ has demonstrated treatment‐response utility207 and has undergone cross‐cultural validation in Chinese populations.208, 209 MOVES has been validated in French210 and Chinese211 contexts. New instruments address previously underrepresented domains: stigma (TDSC),212 sensory phenomena (SPAS),213 and self‐injurious behaviors (Self‐Injurious Behavior Scale for Tic Disorders [SIBS‐T]).214 Machine learning and computer vision approaches show promise for automated tic detection from video,215, 216, 217 with best‐practice methodology for video‐based coding now established.218 The CGI‐S has been evaluated for tic severity but has not demonstrated superiority over the YGTSS.219
Conclusions and Future Directions
The field has progressed through refinement of established scales and expansion into new domains, but fragmentation remains a key limitation. Priorities include harmonized multidimensional frameworks, comprehensive validation across age groups and cultures, integration of clinician‐reported outcomes and PROs, and establishment of longitudinal responsiveness and clinically meaningful change thresholds, particularly for digital tools and newly developed instruments targeting stigma, sensory features, and self‐injurious behavior. Given the lack of harmonization and the early validation stage of most new instruments, an updated review is not yet warranted, though this should be revisited once digital and underrepresented‐domain tools mature.
Construct: PSP
Current State
In 2015, the MDS Task Force reviewed 27 COAs for PSP and recommended 3 instruments—one each for global severity (Progressive Supranuclear Palsy Rating Scale [PSPRS]), motor evaluation (Unified Parkinson's Disease Rating Scale [UPDRS]), and cognition (FAB) (Table 5).220
Gaps Identified
The PSPRS requires further evaluation of content validity, scaling properties, and responsiveness, whereas the UPDRS and FAB lack adequate PSP‐specific validation. Comprehensive tools that address nonmotor and behavioral features are absent, most instruments are English only, and evidence on clinically meaningful change is limited.
New Evidence
Additional PSPRS validation and proposed modifications have been reported.221, 222 The PSP Quality of Life Questionnaire has undergone further validation, including cross‐sectional and longitudinal evaluation of the short and long versions,223, 224 and PQoL Carers has been developed225 and validated in 2 independent cohorts.226, 227 Interest in nonmotor features has grown, with clinimetric studies of cognitive and mood instruments in PSP populations,228, 229, 230 and the Cambridge Questionnaire for Apathy and Impulsivity Traits (CamQUAIT) demonstrating good construct validity for apathy, impulsivity, and behavioral assessment across frontotemporal lobar degeneration (FTLD)–related syndromes, including PSP.231 The PSP Clinical Deficits Scale has been introduced for clinical deficit monitoring232 and shown to accurately reflect functional status and PROs/caregiver‐reported outcomes.233 A functional assessment tool for repeat tauopathies234 and a PSP‐specific screening questionnaire235 have also been published.
Conclusions and Future Recommendations
Recent progress is meaningful but substantial gaps persist, particularly in PSPRS content validity and responsiveness, PSP‐specific nonmotor and behavioral instruments, and caregiver‐reported outcomes. Although CamQUAIT shows promise for behavioral assessment across FTLD‐related syndromes, a PSP‐specific nonmotor instrument remains an unmet need. The current evidence does not meet the threshold for an updated review.
Construct: Diagnosis of RLS
Current State
In 2014, an MDS‐commissioned review evaluated diagnostic instruments for RLS.236 Three tools were recommended (Table 5).
Gaps Identified
Most tools were validated against expert clinical diagnoses, which limits generalizability. Progress since 2014 has focused on refining clinical diagnosis rather than establishing a novel gold standard. A validated pediatric RLS diagnostic instrument is still lacking.
New Evidence
A major conceptual advance was the 2014 update to the International Restless Legs Syndrome Study Group diagnostic criteria,237 introducing a fifth essential criterion requiring the exclusion of alternative medical or behavioral explanations, adding clinical significance and disease‐course specifiers, and unifying pediatric and adult criteria. Multiple translations and cultural adaptations of established instruments have since been published.238, 239, 240 The Single‐Question Screening Tool has been developed and validated in German241 and applied in Norwegian population studies.240 The Restless Legs Syndrome Screening Questionnaire (RLSSQ), published in 2009 but not included in the 2014 review, demonstrated high sensitivity (97.9%) and specificity (96.2%) across diverse validation cohorts with strong mimic discrimination.242 Several new diagnostic tools have been developed in Indian populations to address sociocultural variation and mimic differentiation, including the Indian RLS Diagnostic Questionnaire,243 the Modified‐Restless Legs Syndrome Diagnostic Questionnaire (m‐RLS‐DQ),244 the Hindi Restless Legs Syndrome (RLS‐H),245 and the ARQIP Questionnaire.246 Across these studies, however, sample sizes are small, internal consistency is variable, specificity is limited, and independent replication is lacking.
Conclusions and Future Needs
RLS diagnostic assessment has expanded mainly through translations and population‐specific tools. Future priorities include robust independent validation, systematic inclusion of mimics, cross‐cultural harmonization, and the development of pediatric‐specific diagnostic instruments. Given the small samples and lack of independent replication of new diagnostic tools, an updated review is not warranted.
Construct: Severity of RLS
Current State
The 2014 MDS‐commissioned review evaluating severity rating scales for RLS identified 2 instruments that were recommended (Table 5).247
Gaps Identified
Key gaps include the absence of a validated self‐administered International Restless Legs Syndrome Study Group Rating Scale (IRLS) version, limiting feasibility in clinical and research contexts, and insufficient validation of pediatric severity measures.
New Evidence
The IRLS has undergone multiple translations and cross‐cultural validations, reinforcing its robustness and international applicability.248
The self‐administered IRLS (sIRLS) has now been formally validated as a PRO, demonstrating excellent internal consistency (Cronbach's α = 0.93), good item homogeneity (0.59), and very high agreement with interviewer‐administered scores (intraclass correlation coefficient = 0.94).249 Independent adoption by other research groups addresses a major limitation cited in the 2014 review. RLS symptom diaries have emerged as a complementary approach for capturing daily symptom fluctuations and augmentation, reflecting a broader shift toward longitudinal, ecologically valid tools, though adherence challenges remain.250
Conclusions and Future Needs
The sIRLS validation represents an important methodological advance, addressing the major limitation of the 2014 review. Remaining priorities include pediatric severity validation, optimized PRO formats, and standardized approaches to symptom fluctuation and augmentation monitoring, including diary‐based and digital tools. As pediatric and digital measurement gaps remain unresolved, an updated review is not warranted.
Construct: QoL of RLS
Current State
The 2014 MDS‐commissioned review recommended only the RLS‐QoL (Abetz) for both cross‐sectional assessment and sensitivity to treatment‐related change.251
Gaps Identified
Uncertainty in diagnostic ascertainment, with many participants recruited from support groups without expert‐confirmed diagnoses, compromised the evidentiary strength of otherwise psychometrically acceptable tools. No QoL instrument exists for pediatric RLS.
New Evidence
The Kohnen RLS‐QoL demonstrated high internal consistency, adequate item homogeneity, good test–retest reliability, and responsiveness to clinical change,252 yet validation was conducted by the original developers in clinical trial samples without independent replication. The RLS‐QoL (Abetz) has undergone further cross‐cultural validation, including Turkish adaptation.253 Broader instruments addressing psychosocial and self‐management dimensions, including the Pearlin Mastery Scale,254 Ethos Brief Index,255 and RLS Self‐Care Behaviour Questionnaire,256 highlight conceptually relevant domains beyond symptom burden, though none have been integrated into standard RLS outcome frameworks.
Conclusions and Future Needs
Advances since 2014 have been limited. Future priorities include independent validation of existing instruments; pediatric QoL tool development; consensus on comprehensive QoL domains, including psychosocial and self‐management aspects; and cross‐cultural harmonization. Given the limited and largely nonindependent new evidence, an updated review is not warranted.
Construct: DIMDs
Current State
In 2023, the MDS‐COA Evaluation Committee systematically reviewed 23 outcome measures for DIMDs; none met criteria for “recommended” status, and 7 symptom‐severity scales—3 of which also served as screening tools—were classified as “recommended with caveats.”257
Gaps Identified
Most instruments lack adequate evidence for internal consistency, inter‐rater reliability, and responsiveness, limiting confidence in their use for longitudinal tracking and treatment evaluation. No single scale captures the full spectrum of DIMD across both hyperkinetic and hypokinetic phenotypes. Continued reliance on the umbrella term “extrapyramidal symptoms” reflects an outdated conceptual framework that obscures clinically distinct syndromes and complicates cross‐study comparisons.
New Evidence
Since 2023, a Slovenian translation and further validation of the Drug‐Induced Extrapyramidal Symptoms Scale have been published.258 In parallel, video‐based artificial intelligence approaches have demonstrated high diagnostic accuracy for automated detection of tardive dyskinesia, outperforming trained raters on the Abnormal Involuntary Movement Scale.259
Conclusions and Future Directions
An updated review is not yet warranted, primarily because the 2023 MDS review is too recent for substantial new evidence to have accumulated. The considerable psychometric limitations of existing scales should be addressed through targeted validation studies. Digital and AI‐based tools represent promising complementary approaches for future assessment and monitoring.
Limitations
This review has several limitations. It was designed as a broad evidence‐mapping and prioritization exercise rather than an exhaustive systematic review of each individual construct. First, screening in step 2 was performed by 1 reviewer per construct, with referral of uncertain records to a second reviewer.
This approach may increase the risk of selection error relative to independent dual screening, and relevant studies may therefore have been missed. Second, the searches were limited to PubMed and Web of Science, and studies indexed exclusively in specialized databases such as Embase or APA PsycINFO may have been missed. This risk was partly mitigated by using the previous MDS systematic reviews as the established evidence base, searching from the date of each corresponding review, and examining relevant review articles for eligible primary studies.
Third, records published in languages other than English were assessed based on their English title and abstract only, so extraction of measurement properties for those studies may be incomplete. Fourth, consistent with the evidence‐mapping purpose of a scoping review, methodological quality assessment of individual studies was not performed, and included studies are therefore not weighted by quality in the synthesis.
Conclusion
This review provides an updated overview of COA development across 13 non‐PD movement disorder constructs, with significant advances in digital and remote assessment, PRO expansion, and disease‐specific instrument development. Although the field has shifted from scale development toward validation and implementation, evidence supporting responsiveness and longitudinal performance remains limited across most constructs, underscoring that the primary need is now harmonization rather than new tool creation. Updated systematic reviews are most urgently warranted for tremor, where expanding therapeutic options such as MRgFUS increase the need for COAs with demonstrated sensitivity to treatment‐related change, a property not yet established for most existing instruments, and for dystonia, where new evidence now spans motor severity, nonmotor features, pediatric populations, and task‐specific subtypes.
Future progress will depend on harmonizing existing instruments, establishing clinically meaningful change thresholds, and integrating digital and patient‐centered outcomes into fit‐for‐purpose frameworks for clinical trials and practice.
Author Roles
(1) Research project: A. Conception, B. Organization, C.
Execution; (2) Statistical analysis: A. Design, B. Execution, C.
Review and critique; (3) Manuscript preparation: A. Writing of the first draft, B. Review and critique.
P.T.: 1A, 1B, 1C, 3A
E.P.: 1A, 1B, 1C, 3B
N.K.: 1C, 3B
A.W.S.: 1C, 3B
S.R.D.: 1C, 3B
R.B.: 1C, 3B
C.A.: 1C, 3B
N.V.: 1C, 3B
K.L.O.: 1C, 3B
I.M.: 1A, 1B, 1C, 3A
A.J.E.: 1C, 3B
A.S.F.: 1C, 3B
M.H.S.T.: 1A, 1B, 1C, 3B
M.S.: 1A, 1B, 1C, 3B
T.A.M.: 1A, 1B, 1C, 3B
Disclosures
Ethical Compliance Statement: Institutional review board approval was not required for this work, as it is a scoping review of previously published literature and involved no human participants or individual patient data. Informed patient consent was not necessary for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.
Financial Disclosures and Conflicts of Interest: The Scientific Evaluation Committee of the MDS COA program commissioned this position paper. T.A.M. and A.S.F. report, as support for the present manuscript, a stipend as Director of the MDS COA Program. Conflicts of Interest: The authors declare that there are no conflicts of interest relevant to this work.
Financial Disclosures (past 36 months): P.T.: self‐employed neurologist, private practice in Merelbeke, Belgium; support for attending meetings and/or travel: EAN Congress Finland 2025, supported by Merz Pharma GmbH. E.P.: support for attending meetings and/or travel: The Swedish Parkinson Foundation, Parkinsonfonden, travel support to attend MDS Congress 2025 (payment made to her institution). N.V.: None.
C.A.: grants or contracts: Parkinson Canada (research funding), Biogen (clinical trial contract); consulting fees: Synucure; payment or honoraria: Movement Disorder Society. S.R.D.: payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events, and support for attending meetings and/or travel: AbbVie, Ipsen. N.K.: None.
K.L.O.: None. A.W.S.: grants or contracts: National Institute of Health; consulting fees: VIMA Therapeutics; leadership or fiduciary role: Tremor Research Group. R.B. has received grants from the following agencies: the Thailand Science Research and Innovation (TSRI, Programme Management Unit for Competitiveness, C01F670185); the National Economic and Social Development Council of Thailand, Thailand Centre of Excellence for Life Sciences (TC [ERP] 31/2568); the National Research Council of Thailand (N42A680591, N35E680087); Chulalongkorn University (CE68_028_3000_004); and the Thailand Research Fund.
He is also supported by the Royal Society of Thailand, has provided consultancy services, and has received honoraria and lecture fees from industries such as Britannia, Eisai Pharmaceuticals, Ipsen, Teva‐Lundbeck, and Mitsubishi‐Tanabe. Royalties or licenses: Elsevier Academic Press. Leadership or fiduciary role: Asian Oceanian Association of Neurologists (Secretary and Treasurer); The Neurological Society of Thailand (Chair, International Affairs and Research).
R.B. holds patents for various innovations, including a laser‐guided walking stick, a portable tremor device, technology for monitoring during the night (NIGHT‐Recorder), an electronic diary for Parkinson’s disease symptoms, as well as the Parkinson insole and shoe, and antichoking mugs. Furthermore, his copyrighted works comprise the application for screening Parkinson’s disease (Check PD), a Parkinson’s mascot, a daily activity diary for Parkinson’s disease, creative dopamine‐themed lyrics, and educational video content focusing on common nighttime and gastrointestinal symptoms associated with Parkinson’s disease. A.J.E. has received grant support from the NIH and the Michael J.
Fox Foundation (payments made to institution), and personal compensation as a consultant/scientific advisory board member for Mitsubishi Tanabe Pharma America (formerly Neuroderm), Amneal, Acorda, Acadia, AbbVie, Bial, Supernus (formerly USWorldMeds), NeuroDiagnostics, Inc. (SYNAPS Dx), Intrance Medical Systems, Inc., Merz, Praxis Precision Medicines, Citrus Health, and Herantis Pharma; A.J.E. is Data Safety Monitoring Board (chair) of AskBio and has received publishing royalties from Lippincott Williams & Wilkins, Cambridge University Press, and Springer. He is co‐inventor of the patent “Compositions and methods for treatment and/or prophylaxis of proteinopathies” with which he cofounded REGAIN Therapeutics to fund preclinical studies.
He has no financial relationship with the company and has relinquished the right to any personal income from future treatments. A.J.E. owns no stock in any pharmaceutical company with which he has an advisory relationship. T.A.M. reports stipend: Director MDS COA Program; consulting and Advisory Board Membership with honoraria: AbbVie, International Parkinson and Movement Disorder Society, CHDI Foundation/Management, Roche, WAVE, and PTC Therapeutics; grants and research: EU Joint Program‐Neurodegenerative Disease Research, uOBMRI, Roche, Ontario Research Fund, CIHR, the Michael J.
Fox Foundation for Parkinson’s Research, Parkinson Canada, Parkinson Research Consortium, and Brain Canada; salary: UOMA. A.S.F. reports receiving a salary from Hospital 12 de Octubre and a stipend as Director MDS COA Program. He holds patents, receives salary, and holds shares in Leuko Labs, Inc./Leuko Imaging Systems.
Patents issued: US Patents 12,383,155; 12,216,112; 12,131,217; 11,963,750; 11,860,154; 11,445,980; 10,959,676; 10,506,979. He receives royalties from patent US20150272504A1, Elsevier, and Digital Technologies in Movement Disorders (Book). He has received speaker honoraria from AbbVie, Abbott, Alter, Bayer, Bial, Boston Scientific, Esteve, the European Academy of Neurology (EAN), Italfarmaco, Medtronic, the Movement Disorder Society (MDS), Novartis, Organon, PD Monitor, Roche, the Spanish Society of Neurology (SEN), Stada, Teva, and Zambon.
He has served as a consultant or advisor for AbbVie, Boston Scientific, Esteve, Lundbeck, Orion Pharma, Roche, Prim, and Zambon. Participation on an Advisory Board: Hoffman La Roche. He has received research funding from ERA‐NET Horizon 2020 JPCOFUND2 (HESOCARE‐329‐073), the Spanish Research Agency/Instituto de Salud Carlos III (PI22/01177), EIT Health (PDNetGo), NIH (SBIR grant), and the MDS (eDiary); clinical trial agreements: Hoffman La Roche, Zambon, Ferrer, TEVA Pharmaceuticals.
Support for attending meetings and/or travel: MDS, IAPDR, SEN LIMPE, Parkinson Study Group. Leadership or fiduciary role: Chair, Movement Disorders Group, Spanish Neurological Society; Director, COA Program at MDS. M.H.S.T. receives a salary from Rush University and is part of a working group supported by the International Parkinson and Movement Disorder Society.
Grants or contracts (payments made to Rush University): International Parkinson & Movement Disorder Society; NINDS (1U01NS143225, 1R01NS135614‐01A1, 5R01NS125294); HHS/NIH (PAF08839); CHDI Foundation; NIA (1R01AG059417‐01A1); NeuraLight Inc. Consulting fees: International Parkinson & Movement Disorder Society (payments made to her). Leadership or fiduciary role: International Parkinson & Movement Disorder Society (unpaid).
M.S. receives funding from the EU Renewal and Resilience Plan “Large projects for excellent researchers” under grant number 09I03‐03‐V03‐00007, from the Slovak Research and Development Agency under contract number APVV‐22‐0279, and from Vedecka grantova agentura. Over the past 12 months, M.S. has received speakers’ honoraria from AbbVie, Biogen, Desitin, Medtronic, Krka, Medis, IPMDS, Stada, and Sandoz. He is an advisor to AbbVie and Biogen.
Consulting fees: AbbVie, Medis, Biogen, Medison, Medtronic, UCB, Stada. Participation on a Data Safety Monitoring Board or Advisory Board: AbbVie, Medis, Biogen, UCB, Stada, Medtronic. Leadership or fiduciary role: Medical Faculty UPJS Kosice; Slovak Neurological Society.
I.M. receives research funding from Region Stockholm, Karolinska Institutet and Parkinsonfonden. Payment or honoraria: AbbVie educational seminar. Support for attending meetings and/or travel: AbbVie advisory board (travel and hotel stay).
Participation on an Advisory Board: AbbVie (institutional fees). Author disclosures are available in the Supporting Information.
Supporting information