Linear and nonlinear tremor acceleration characteristics in patients with Parkinson's disease

Abstract

The purpose of the study was to evaluate linear and nonlinear tremor characteristics of the hand in patients with Parkinson's disease (PD) and to compare the results with those of healthy old and young control subjects. Furthermore, the aim was to study correlation between tremor characteristics and clinical signs. A variety of nonlinear (sample entropy, cross-sample entropy, recurrence rate, determinism and correlation dimension) and linear (amplitude, spectral peak frequency and total power, and coherence) hand tremor parameters were computed from acceleration measurements for PD patients (n = 30, 68.3 ± 7.8 years), and old (n = 20, 64.2 ± 7.0 years) and young (n = 20, 18.4 ± 1.1 years) control subjects. Nonlinear tremor parameters such as determinism, sample entropy and cross-sample entropy were significantly different between the PD patients and healthy controls. These parameters correlated with the Unified Parkinson's disease rating scale (UPDRS), tremor and finger tapping scores, but not with the rigidity scores. Linear tremor parameters such as the amplitude and the maximum power (power corresponding to peak frequency) also correlated with the clinical findings. No major difference was detected in the tremor characteristics between old and young control subjects. The study revealed that tremor in PD patients is more deterministic and regular when compared to old or young healthy controls. The nonlinear tremor parameters can differentiate patients with PD from healthy control subjects and these parameters may have potential in the assessment of the severity of PD (UPDRS).

Intraoperative acceleration measurements to quantify improvement in tremor during deep brain stimulation surgery

“…like the ones proposed in this study have been shown to correlate with the UPDRS tremor scores during routine non-surgical clinical evaluation [20].…”

“…Gravity also has an effect on the data measured by the accelerometer [30] and therefore has to be corrected for before any outcome measures are extracted. In contrast to previously proposed methods, in which the effect of gravity was not suppressed, our method uses a cutoff frequency of 2 Hz for the smoothness-priors detrending method which has been shown to suppress the effect of gravitational acceleration on the raw data [20]. With regard to the outcome measures, as Papapetropoulos et al [27] used a commercial system; they were restricted to the outcome measures available from it, i.e., tremor intensity, center frequency, its standard deviation, and harmonic index.…”

“…(1) A time-varying high-pass filter called "smoothness priors" [48], with a cutoff frequency of 2 Hz [20], was used to remove low-frequency trends and the effect of gravity. (2) format.…”

“…Accelerometers have been applied outside the operating room (OR) for a wide variety of purposes, e.g., to characterize pathological tremor [8,13], to compare it with physiological tremor [20,35,36], and to evaluate the severity and evolution of tremor [28,29,40] and the tremor-alleviating effect of drugs or DBS [22,36,47]. Pulliam et al [34] used motion sensors during postoperative DBS pulse generator programming to develop automated programming algorithms and concluded that objective assessment can improve patients' outcomes.…”

Development of an Infant’s Peripheral Motor System Within the First 3 Years of Life as Studied Using Surface Electromyography

“…Для реализации поставленной цели применена накожная неинвазивная электромио-графия (ЭМГ) с новыми нелинейными и традиционными линейными параметрами сигнала [4,16,17].…”