Quantitative Assessment of Cerebellar Ataxia With Kinematic Sensing During Rhythmic Tapping

The aim of this study is to investigate the validity of an entropy-based objective assessment of cerebellar ataxia patients performing rhythmic tapping. Previous research conducted, particularly in time and frequency domains, tested the adherence of patients to more stringent experimental requirements. These requirements may inadvertently cause higher level brain functions to influence the performance and possibly obscure the cerebella related disabilities in the data stream. In this study, a multiscale entropy-based learning process that overcomes this practical limitation was considered. In particular, assessment techniques with less restrictions on the tapping duration were considered. Thirty-three patients were engaged in the test, with three levels of severity 0 (normal), 1 (moderate) and 2 (severe) ranked by specialist clinicians. The performance of each model was evaluated using leave-oneout cross validation. Results from both time-frequency features and entropy features extracted and characterized the cerebellar condition captured during the finger and foot tapping tests (with over 80% accuracy). Strong correlations with clinical assessment-based scoring were observed with the entropy based approach for both tests, although the correlation with time-frequency features were less convincing.

I. Introduction

Cerebellar disorders are usually assessed by the performance of standard motor tasks that involve rapid, repetitive or alternating movements of the limbs. Repetitions such as tapping or producing repetitive labial or plosive sounds are mostly referred to in neurological assessments. In the Croonian Lectures of Gordon Holmes [1] , a number of fundamental motor deficits in cerebellar dysfunction were described. Disturbances in the range (dysmetria) and rate of movement are most likely the cause of this variability. Cerebellar dysfunction appears to disrupt movements that require intermittent timing (e.g. tapping) rather than those with single timing process (e.g. repeated drawing of a circle in the air) [2, 3, 4]. Cueing and multiple joint requirement should also be mentioned in characterizing cerebellar abnormalities, where the involvement of multiple joints increases the errors in timing and accuracy. Whether or not auditory cueing improves timing in cerebellar dysfunction remains unclear [2 , 4] .