Objective: To detect subtle postural sway deficits in FMR1 premutation carriers who are asymptomatic for signs of FXTAS and determine the impact of dual tasking and sensory manipulation on balance in FXTAS.

Background: FXTAS is a neurodegenerative disorder occurring in some Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene premutation carriers (PMC) and is characterized by cerebellar ataxia, tremor and cognitive deficits which negatively impact balance and increase fall risk. Dual-task (DT) cognitive-motor paradigms may have the capacity to reveal impairments not present under single-task (ST) conditions. Markers of FXTAS onset are needed to provide preventative treatment interventions.

Method: Participants with FXTAS (n=33; 68.6 + 9.5 years), PMC without FXTAS (n=34; 54.9 + 9.5 years) and controls (n=48; 64.0 + 10.5 years) underwent balance testing using an inertial sensor system (APDM^TM). Stance (feet apart (FA)/together (FT)), vision (eyes open (EO)/closed (EC)), surface stability (firm/foam), and cognitive demand (ST/DT) were manipulated in 30 second trials. A concurrent verbal fluency task, the Controlled Oral Word Association Test, was used in DT conditions. Kruskal Wallis analyses with FDR corrections were first performed, followed by a regression analysis controlling for age and MoCA scores.

Results: FXTAS subjects had significantly greater total sway area, jerk, and RMS sway under almost all test conditions, but less dual-task costs (DTC) for jerk than controls during the FTEC condition (p=0.036). PMC without FXTAS had significantly greater RMS sway (measure of sway variability) compared to controls in the ST/FAEC (p=0.035), DT/FAEO (p=0.037), and DT/FTEC (p= 0.049) conditions. In several conditions, PMC without FXTAS were approaching the FXTAS level of balance dysfunction.

Conclusion: Postural sway deficits in the RMS variability domain under EC and DT conditions in asymptomatic PMC might represent prodromal signs of FXTAS. Participants with FXTAS had reduced DTC for jerk suggesting balance was prioritized over cognition while dual tasking. This information may be useful to provide sensitive biomarkers of FXTAS onset, and in designing treatment strategies to improve balance and prevent falls in FXTAS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-dual-tasking-and-sensory-manipulation-on-balance-in-fragile-x-associated-tremor-ataxia-syndrome-fxtas-and-potential-prodromal-postural-sway-deficits-in-asymptomatic-fmr1-premutation-carrie/