Ataxia Rating Scales May Not Measure Up Across Cultures, Researchers Warn

When a neurologist asks a patient to walk heel-to-toe across a hospital corridor, trace an Archimedes spiral with a pen, or repeat a phrase so its slurring can be judged, the resulting score is supposed to measure one thing only: the severity of cerebellar dysfunction. But a new perspective article argues that this assumption may be quietly failing in much of the world. Writing in Frontiers in Neurology, a team of Indian movement-disorder specialists contends that the two most widely used clinician-rated ataxia scales, the Scale for the Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS), may not yield equivalent measurements across linguistically, educationally and culturally diverse populations, even after careful translation. The authors, from the All India Institute of Medical Sciences in New Delhi, the National Institute of Mental Health and Neurosciences and St. John’s Medical College in Bangalore, writing on behalf of the Movement Disorders Society of India National Ataxia Network, introduce the concept of “contextual validity” to describe what translation alone cannot deliver.

The stakes are no longer academic. Hereditary cerebellar ataxias are individually rare but collectively affect an estimated one in 10,000 people worldwide, and the arrival of disease-modifying therapies and gene-targeted clinical trials has turned standardized outcome measures into the currency of drug development. SARA, developed in 2006 at the University Hospital Bonn in Germany, and ICARS, created in 1997 by the Ataxia Neuropharmacology Committee of the World Federation of Neurology with its principal development center in Lyon, France, are the most extensively validated and widely adopted instruments in ataxia studies. Both quantify deficits in gait, stance, limb coordination, eye movements and speech through direct observation of task performance. Because they rely on what an examiner sees rather than on what a patient reports, they are widely assumed to be more objective, and less culture-bound, than patient-reported outcome measures. The new analysis challenges that assumption at its foundation.

The authors systematically examined published translations and adaptations of SARA and ICARS across Europe, South America, North America and Asia, from a Russian version in 2026 to a Japanese SARA from 2009. What they found was strikingly uniform: virtually every adaptation relied on forward and backward translation, expert review and assessment of linguistic, conceptual or cultural equivalence. Some teams refined wording for task clarity, adopted gender-neutral phrasing, or suggested age-adjusted cutoff values; the Korean ICARS group noted but did not correct an unspecified spiral size. Crucially, the review found limited evidence that any adaptation substantively modified the assessment tasks or procedures themselves to address contextual factors beyond language. In other words, the instruments have been carried around the world largely intact, with their task demands, testing conventions and implicit cultural assumptions embedded in the scoring sheets.

Why does this matter? Because performance on these scales, the authors argue, is the product of a three-way interaction between examiner, participant and testing environment, not a pure readout of neurological function. Tasks such as gait, stance, finger chase, heel-shin sliding, rapid alternating hand movements and speech all depend on comprehension of standardized verbal instructions, familiarity with the requested activity, examiner demonstration, participant motivation and culturally patterned styles of communication. When instructions are translated, paraphrased or supplemented with demonstrations in the clinic, as they frequently must be, the task itself may shift in interpretation or execution, introducing variability that has nothing to do with the cerebellum. A scale can be linguistically flawless and still be contextually non-equivalent if task familiarity or examiner interaction systematically moves the numbers.

India, the authors’ exemplary case, illustrates the scale of the problem. The country’s census data record 19,569 reported mother tongues, rationalized into 1,369 linguistic varieties, 121 major languages and 22 constitutionally recognized scheduled languages. Patients and examiners at tertiary referral centers often do not share a primary language, so assessment may depend on examiner-mediated, real-time translation of the original English instructions, with phrasing and terminology varying from assessor to assessor and site to site. Speech assessment compounds the difficulty: SARA and ICARS score fluency, articulation and phonation, yet accent, pronunciation, prosody and articulation differ markedly across regions, sometimes across small geographic areas. An examiner unfamiliar with a patient’s regional speech pattern could misread habitual dialectal features as dysarthria, conflating lifelong linguistic exposure with neurological impairment.

Educational heterogeneity adds another layer. According to India’s Periodic Labor Force Survey 2023-24, roughly one-fifth of the population aged seven and above, 19.1 percent, is not literate, with the proportion nearly twice as high among women, 25.2 percent, as among men, 12.8 percent. The PLFS 2025 reports that 32.2 percent of people aged 15 and above have not attained secondary education, with sharp rural-urban and sex-based gradients, and the National Family Health Survey 2023-24 finds that 53.6 percent of women and 45.4 percent of men nationally have not completed ten or more years of schooling. These figures matter for ataxia rating because some scale items presuppose skills acquired through formal education. The ICARS spiral-drawing task, for example, assumes familiarity with pen-and-paper graphomotor activity that people with little schooling, manual occupations or rural backgrounds may rarely have practiced, a familiarity that rising smartphone use may further erode in some groups. Poor spiral performance could partly reflect unfamiliarity with the medium rather than limb ataxia.

Cultural practice reaches into the examination room as well. India’s documented diversity spans 4,635 distinct communities, and garments such as sarees, mekhela chadors, dhotis, lungis, mundus, ghagras and burqas remain widely worn. During gait, stance and heel-to-knee testing, such attire may alter stride length, lower-limb excursion or balance independently of cerebellar disease, and some patients may prefer not to modify traditional dress for personal, cultural or religious reasons. Neither SARA nor ICARS offers explicit guidance on attire or footwear, yet whether a patient walks barefoot, in slippers or in shoes can itself change gait characteristics and postural stability. Local logistics matter too: tandem gait on an unfamiliar polished hospital floor, examinations squeezed into crowded outpatient areas lacking a ten-meter walking space, and oculomotor scoring that depends on target positioning, velocity, distance and illumination none of the scales explicitly specify, all threaten between-site consistency in multi-center studies.

The consequences for clinical trials could be substantial. SARA is increasingly used as a primary or secondary endpoint in natural history studies and interventional trials of emerging therapies for hereditary ataxias, and such studies assume that a given score represents the same degree of impairment regardless of a participant’s background. If contextual factors systematically influence task performance, observed differences between centers or countries may reflect measurement artifacts rather than biological variation, distorting estimates of disease progression, treatment effects, sample-size calculations and the interpretation of clinically meaningful change. The authors are careful to note that this does not require retrospective modification of established outcome measures; rather, item-level performance analysis, examination of between-center variability, standardized multilingual scripts, examiner training and certification, and harmonized testing procedures can address many sources of contextual variability within ongoing studies without changing the scale itself.

Looking forward, the perspective outlines an ambitious adaptation agenda. Robust cross-cultural adaptation, the authors argue, should extend beyond translation to include cognitive debriefing, pilot testing and comprehensive psychometric evaluation, benchmarked against established frameworks such as COSMIN, with the adapted instrument demonstrating inter- and intra-rater reliability, construct and criterion validity, responsiveness to clinical change and measurement invariance against the original. They propose multi-centric collaborations among neurologists, rehabilitation specialists, psychologists, linguists and patient representatives, and suggest that AI-enabled multilingual platforms could deliver standardized, language-specific instructions while retaining clinician-led scoring. AI-assisted speech analysis might eventually quantify acoustic and temporal features to help separate neurological dysarthria from dialectal variation, though the authors stress such tools would require rigorous validation across languages, dialects, educational backgrounds and recording environments. Wearable sensors and digital biomarkers in home and work environments could complement clinic-based scales and dampen context-specific effects, while validation studies should probe measurement equivalence at both the total-scale and individual-item level, since verbally mediated tasks are likely more vulnerable than simple motor ones.

The authors’ bottom line is a reframing of what a neurological outcome measure owes its users: it should quantify cerebellar dysfunction, not linguistic, educational, cultural or experiential difference. Although the argument is anchored in India, whose combination of a large affected population, expanding molecular diagnostic capacity and growing participation in international research makes it a compelling test case, the principles apply wherever clinician-administered neurological scales cross linguistic and cultural boundaries, and to performance-based measures in other neurological disorders as well. The goal of cross-cultural adaptation, they conclude, should not be to make a scale linguistically familiar, but to ensure that the same neurological impairment produces an equivalent measurement regardless of the context in which it is assessed, a prerequisite for equitable patient care, high-quality multi-center research and fair evaluation of the therapies now entering the ataxia pipeline.

Subject of Research: Cross-cultural validity of clinician-administered ataxia rating scales

Article Title: Are clinician-administered ataxia scales truly culture-free? Rethinking contextual validity in diverse populations

Article References: Narzari, H., Yadav, R., Srivastava, A. K., Pal, P. K., & Garg, D. (2026). Are clinician-administered ataxia scales truly culture-free? Rethinking contextual validity in diverse populations. Frontiers in Neurology, 17, Article 1991845. https://doi.org/10.3389/fneur.2026.1991845

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1991845

Keywords: ataxia, SARA, ICARS, cerebellar ataxia, contextual validity, cross-cultural adaptation, clinical outcome measures, psychometric validation, measurement invariance, India, clinical trials, movement disorders