Neuromotor tests

Walking and balance tests were performed during remote visits at participants' homes using wearable sensor technology (OPAL™ System; APDM, Portland, OR). For remote visits, a laptop, web camera, and an OPAL system kit were mailed to participants prior to the prescheduled visit date. A written manual was provided to the participant prior to testing that included step‐by‐step instructions on the setup and operation of all equipment and an accompanying picture‐based guide. The walking and balance tests and the ataxia rating scale were also depicted in the manual. Visits took place via secure connection through Zoom™. Zoom allows the study staff to remotely control the operation of the OPAL system software during testing. Trials were supervised by two trained study staff members remotely via web camera, so although study staff were not present on site, it was possible to repeat a test as needed if a sensor alert occurred, or if the test instructions were not executed according to protocol.

During the 1‐h scheduled visit, quantitative measures of gait and balance were obtained using the OPAL sensors. The system consists of three watch‐sized battery‐based accelerometers that submit synchronized signals to a central sensor through ultra‐low power radio frequency waves not known to cause any harm. The accelerometers were placed on the participants' waist and feet during the assessments. Two trials were collected for each walking and balance test during the visit following the established OPAL System protocols. 8

To setup the Walk Test, participants were instructed to designate a level, unobstructed walking path of 20 ft in their home and mark the start/stop points with a marker and measuring tape provided in the kit. To assess gait, a 2‐min Walk Test was performed, during which the participant walks in a straight line at a comfortable, natural pace, turns around at the stop point, and walks back to the original start point over a duration of 2 min. MobilityLab software was used to analyze the walk trials according to proprietary algorithms (APDM).

Four variations of the Balance Test were conducted to measure the participants' postural sway while standing still for 30 sec. The participants stood with their eyes open with their feet apart, eyes open with their feet together, eyes closed with their feet apart, and eyes closed with their feet together. The OPAL kit included a foot plate that was used to standardize stance width with the feet apart. MobilityLab software was also used for the analysis of the balance trials (APDM).