Objective assessment of tremor in Parkinson's disease using the RehaBEElitation serious game

Parkinson's disease (PD) is a neurological disorder that affects body movements, and tremor is often the first and the most troublesome motor symptom of the disease. Currently, the most widely used clinical scale for the assessment of tremor is the Movement Disorder Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRS). However, this type of assessment carries limitations, such as its subjectivity and dependence on experienced evaluators. These problems can be overcome by using inertial sensors for objective measurements of movement. Therefore, a serious game called RehaBEElitation for upper limbs was developed, with which users interact using a glove composed of inertial and resistive sensors. This study aimed to evaluate tremor objectively using the RehaBEElitation. Fifteen individuals with PD and fifteen healthy individuals interacted with the game, constituting the experimental group (EG) and control group (CG), respectively, matched in age and sex. Data collection was performed in the ON and OFF states of medication for the EG. Tremor was detected by removing the trend from the original signal and was assessed by estimating the Mean Absolute Value (MAV), Root Mean Square (RMS) and Power Spectral Density (PSD) of the gyroscope signals. The probability that the peak frequencies of the PD-OFF signals fall within the frequency range of Parkinson's tremor (4–7 Hz) was higher than for the PD-ON group, which in turn was higher than for CG. For both MAV and RMS, the chance that the distribution having a bimodal aspect, which represents the presence of PD tremor, was higher for the EG in the ON and OFF states than for the CG. The PD-OFF group had the highest probability of having the highest peak power in the signal than the other groups. In summary, MAV and RMS showed strong correlation with MDS-UPDRS. The RehaBEElitation serious game is an alternative tool to assess hand tremor objectively and playfully. The EG participants in the OFF state presented more tremor compared to the ON state.