Objective: To determine correlation between the Fragile X-associated tremor ataxia syndrome (FXTAS) staging system and the FXTAS rating scale

Background: FXTAS is an X-linked, neurodegenerative disorder that causes intention tremor, gait ataxia, and cognitive decline. Salient features of the disease are captured by the FXTAS rating scale. The FXTAS staging system was proposed to describe the extent of disability of a FXTAS patient, based on neurological signs, activities of daily living, and mobility status. This staging has never been studied to determine if tracks with disease progression compared to validated measures.

Method: Consecutive FXTAS patients seen at the Rush FXTAS clinic for clinical care (7/2024 to 3/2025) were evaluated using the FXTAS staging system, after interview and neurological examination. Administration of the FXTAS Rating Scale (version 2) was also performed. Descriptive statistics were used to determine demographic information. Regression was used to determine correlation of the FXTAS stage to the FXTAS rating scale total score, adjusted by age, sex, duration of disease and CGG repeat size.

Results: Twenty-two patients were included: 7 with definite FXTAS, 12 with probable FXTAS, and 3 with possible FXTAS. Average age was 68.6± years, 59% were men, average premutation CGG repeat size was 83±20.1, average duration of disease was 8± 5.8years, and average FXTAS rating scale total score was 27±11.4. FXTAS stage scores 2, 3, and 4 were significantly associated with total FXTAS Rating Scale score in univariate analysis (p=0.03). However, when adjusting for age, sex, and CGG; significance was lost (p=0.06). Disease duration was also highly correlated with FXTAS stage (p=0.01) and when included in the model, FXTAS Stage was not associated with the FXTAS Rating Scale score.

Conclusion: FXTAS Rating Scale score is not correlated with the FXTAS Staging system, but instead correlates with disease duration. This is different than staging for other movement disorders, like the MDS-UPDRS for Parkinson’s disease, in which increasing score correlates with an increase in Hoehn & Yahr stage score. This suggests that revision of the FXTAS Staging system is warranted. A larger sample size with a wider spread of disease duration and signs is also needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/correlation-of-the-fxtas-staging-system-and-the-fxtas-rating-scale/