Quantitative measures of postural tremor at the upper limb joints in patients with essential tremor

Abstract

BACKGROUND: It is important to quantitatively assess tremor for accurate diagnosis and evaluation of the response to interventions in patients with essential tremor (ET). OBJECTIVE: The purpose of this study was to investigate the relationship between quantitative measures of postural tremor and clinical rating scale in patients with ET. METHODS: 18 ET patients performed a postural tremor task that required them to hold their arms outstretched parallel to the floor while wearing a gyro sensor based measurement system. The time domain variables were derived from the sensor signals. Additionally, the frequency domain variables were derived from the power spectrum of the angular velocity signal. Spearman correlation analysis was employed in the relationship between the variables and clinical score. RESULTS: The RMS angular velocity of roll and yaw directions at the hand joint were strongly correlated with the clinical rating scale (r = 0.7, p < 0.01). Similarly, the peak power of roll and yaw directions at the hand joint were moderately correlated with the clinical rating scale (r = 0.61 and r = 0.67, p < 0.01). In contrast, no significant correlation coefficients were observed in the peak frequency (p > 0.05). CONCLUSION: These results indicate that hand tremor of roll and yaw directions are more associated with assessment of severity of ET compared to other joints. This study suggests that quantitative measurements of postural tremor should be considered as tremor directionality as well as attachment location.

Assessment of upper limb movement disorders using wearable sensors during functional tasks: a systematic review

“…Additionally, Heldman et al found a correlation of -0.78 between RMS angular velocity values and the modified bradykinesia rating scale[101] and Salarian et al found good correlation between RMS angular velocity values and the UPDRS bradykinesia subscore, as well as good correlation between RMS angular velocity of the roll axis and the tremor subscore of the UPDRS[52]. In patients with tremor, spearman correlation between RMS angular velocity and tremor severity scores ranged from 0.19 (finger-tonose) to 0.73 (keeping arms extended in front of the body) for Lopez-Bianco et al[108] and between 0.41 and 0.70 for Kwon et al[110], whereas Heo et al found lower RMS angular velocity values after electrical stimulation[105].Seventeen studies reported mean acceleration as a feature, but only two PD studies and one ataxia study discussed its sensitivity. Romano et al found lower mean acceleration for PD patients in comparison with the control group, while Zwartjes et al did not find significant differences between ON and OFF stimulation states of deep brain stimulation[57,90].…”

“…Twelve studies included patients with essential tremor [102][103][104][105][106][107][108][109][110][111][112][113] and 11 included adults post-stroke [15,28,[114][115][116][117][118][119][120][121][122], whereas six included adults with MS [123][124][125][126][127][128]. One study included adults with HD and eight studies included children or adults with ataxia [29,[129][130][131][132][133][134][135][136].…”

“…For the studies where both acceleration and angular velocity signals were collected, both mean and standard deviation (STD) were often calculated [62,78,86,87,90,118,129,139], as well as rootmean-square (RMS) values [11,86,89,129,139]. Additionally, mean and RMS or STD of acceleration and angular velocity separately were used in studies were one of the signals was available [29,50,52,54,57,63,64,66,71,74,82,83,85,89,96,104,105,108,110,111,115,119,120,[132][133][134]137], as well as median angular velocity in one study [82]. Maximal linear velocity was additionally often used as key feature, mostly by integration of the acceleration signal [51,54,115].…”

“…; [62] Stroke [15], PD [62], ataxia [129] Amplitude and dominant frequency of modulation associated with acceleration PD [49] Average magnitude of 1 st five STFT components HD [29] Fractal dimension acceleration PD [49] Spectral power Frequency band 1.5-3Hz & 5-8Hz [118]; Frequency band dyskinesia: 0.3-3Hz [77]; Frequency band 0.5-15Hz & 1-4Hz [87]; Frequency band 0.6-16Hz [140]; Welch PSD of displacement; Power Spectral Density plots [68,84]; PSD ratio 0.5-4Hz & 4-12Hz [102]; logarithm of the peak in the power spectrum in the tremor frequency band [113] Stroke [118], PD [68,77,84,87], dystonia [140], tremor [102,113] Peak power Gyroscope; 0-4Hz frequency band [73]; Power of dominant frequency [87]; Position and amplitude of dominant peaks in power spectra of acceleration signals [104] PD [59,60,73,87,99], tremor [102,104,105,110], ataxia [134], MS [125] Second peak power Power of second dominant frequency [87] PD [87] Total power Power spectrum of angular velocity [59]; Gyroscope; 0-4Hz frequency band [73]; power ratio AC...…”

“…Similarly, Summa et al reported increases in peak power in ON vs OFF medication state[73]. In essential tremor, Heo et al reported higher peak power after electrical stimulation[105] and Kwon et al reported high correlation between peak power and tremor severity scores[110].Sample entropy was included in 11 studies, but only two PD studies reported its sensitivity. Chelaru et al found significantly higher entropy for dyskinetic PD patients in comparison with non-dyskinetic PD patients, as well as Liu et al who found a significant difference between PD patients and healthy controls and good correlation with UPDRS scores[55,70].…”