Article Preview
Top1. Introduction
Electromyography (EMG) is the quantification of the electrical activity of the muscles and this provides a measure of the muscular contraction. After a series of works conducted to discern and distinctly analyze Essential Tremors (ET), Louis ED (2001a) concluded that these are transferred to successive generations through autosomal dominant transmissions and is mutagenic .These tremors originate from the central nervous system and are more evidently observed by the involuntary contractions of muscles even during activity. Various other EMG tremors like, postural tremor of the outstretched arms, intentional tremor of the arms and rest tremor in the arms are also not very uncommon in ET (Louis ED, 2001b). Unlike resting tremors observed in Parkinson’s disease, Essential tremor has a unique frequency range of 4-12 Hz and is observed predominantly when the affected muscle is under work (Busenbark et al., 1999;Louis et al., 2000;Ctrichley 1949). Physical and mental stress may further exacerbate the ET.
ET and the resting tremors of Parkinson’s disease (PD) can be Interpreted based on the degenerated part of the brain. Essential tremors originate due to the degeneration of the cerebellum in the brain whereas resting tremors of PD originates due to the degeneration of the Hypothalamus. On extensive experimentation carried out across the globe it is concluded that patients affected with ET may gradually develop Parkinson’s as the risk of Parkinsonism is greater with patients of ET. Resting tremors last longer than the ET, for up to 8-9 seconds and the ET are generally postural and action tremors and they originate bilaterally and the tremor duration is only 1-2 sec (Pahwa et al., 1993).
Despite the fact that, research conducted so far in various parts of the world had been able to successfully differentiate ET and Resting tremors of PD, the scope for intense research is still open. The various stages of ET namely, definite Essential tremor, Probable essential tremor and Possible ET with the progress of tremors from head and neck in the first stage to arms in the second and the third stage is the tremors present during action and rest or continuous tremors in the arms (Kollet et al., 1989) which later progresses to other parts of the body which are yet to be recognized quantitatively through computer aided procedure.
Several works on EMG based tremor detection have been reported in the literature (Lingmei et al., 2011;Arvind et al.,2010; O'Suilleabhain et al., 1998; Hossen et al., 2010). Lingmei et al.,(2011) have applied single value decomposition to extract intrinsic mode function feature to distinguish Parkinsonian tremor from ET . Arvind et al., (2010) investigated the effect of PSD feature estimation by Welch and Burg’s method on resting tremor. O'Suilleabhain & Matsumoto (1998) have discussed the effect of time-frequency analysis on essential, psychogenic and Parkinsonian tremors . Robichaud et al., (2009) investigated the effect of EMG signal as a biomarker for detection of Parkinson detection . Hossen et al., (2010) have proposed wavelet based decomposition for discriminating Parkinson and essential tremors. Woods et al (2014) showed significant differences in postural tremors with different attention and distraction tasks. The effect of influence of noise on EMG based essential tremor was reported (Seki et al., 2011). A specific quantification study has been proposed by Matsumoto et al., 2017 for EMG based essential tremor. A support vector machine based PD and ET classification was reported Haji et al., 2016.