Validation of the tremor biomechanics analysis laboratory (TREMBAL) software in MS tremor

Abstract

Type: Poster

Abstract Category: Clinical aspects of MS - Clinical assessment tools

Background: Tremor in MS (MST) is difficult to treat and the development of new interventions is limited by the absence of universal measuring systems. At present, therapeutic outcomes are measured by a variety of clinical rating scales that are subjective and lack sufficient sensitivity. With increasing use of interventional treatments such as Botulinum toxin injections or Deep Brain Stimulation for MST, it has become critical to develop precise measurement instruments.

Objective: To clinically validate the TREMBAL software in MST.

Methods: TREMBAL (Bionics Institute, Melbourne, Australia) utilises an electromagnetic motion tracker (Ascension, Vermont, US) to acquire absolute displacements and rotations of a tremulous body part. Tremor was recorded bilaterally from four locations (second phalanx of the middle finger, wrist dorsum, forearm and upper arm) in five positions (hands resting on lap, arms outstretched in front, finger-nose, batwing static and batwing action). Tremor exercises were video recorded (GoPro Hero3, GoPro Inc., San Mateo, California) and rated by two experts using the 5-point Unified Tremor Rating Assessment (UTRA) scale where 0=no tremor and 4=severe. TREMBAL tremor displacements (measured in units of millimetres) were averaged and log transformed to match the distribution of clinical ratings. Data were pooled across exercises. Congruence between TREMBAL measures and mean clinical ratings was explored using regression analysis and Pearson´s correlation.

Results: We assessed ten MST patients over 6 months and rated 200 videos. The median pooled UTRA score was 0.5 (interquartile range 0, 1.5). The average TREMBAL recorded tremor displacement was 1.65 mm (standard deviation 2.1). A strong correlation between UTRA scores and log transformed TREMBAL displacement was found, r = 0.749, p< 0.001.

Conclusions: TREMBAL measurements are highly accurate when compared to clinical measurements. While other objective tremor measures exist, only a few have been benchmarked specifically against MST clinical ratings. The validation of an objective, 3 dimensional tremor measurement system provides real-time tremor severity measurements for clinicians and can be applied in clinical trials of putative therapies for MST.