View/Open - Scholarly Commons Home

Chapter 1 - Introduction
ET is typically characterised by a kinetic tremor that has a frequency of
4-12Hz, however postural and intention tremor may also be present (R.
Elble, 2009; Louis, 2005, 2010b). This disorder commonly affects the
upper limb but may also occur in lower limbs, head and voice (Lorenz &
Deuschl, 2007; Louis, 2005). Though the pathology of ET is not fully
understood, it may reflect dysfunction in the olivocerebellar and
thalamocortical pathways (R. J. Elble, 2009). Sensorimotor
characteristics of ET can include abnormal entrainment of motor unit
activity at the frequency of the tremor, and inappropriate patterns of
agonist-antagonist muscle activation and reduced force steadiness of
the digits (M. E. Héroux, Pari, & Norman, 2010; Lundervold & Poppen,
2004b). These sensorimotor changes may contribute to the kinetic
tremor in combination with postural tremor commonly seen in ET. This
can have a considerable negative impact on function such as
manipulating and reaching. Such movements are part of a number of
daily living activities including eating, drinking, and writing (W. C. Koller,
Busenbark, & Miner, 1994; Louis, et al., 2001; A. Rajput, Robinson, &
Rajput, 2004). ET patients often experience a loss of hand and finger
dexterity, and as a result disability due to a loss of independence and
even incapacitation (Louis, 2005). This disability and loss of
independence with ET can dramatically effect psychosocial status, with
significant declines in QoL evident (Deuschl & Elble, 2009). Furthermore,
alterations to eye-hand coordination (Trillenberg, et al., 2006), eye-blink
reflex (Deuschl & Elble, 2009) and disturbances in cognitive function
have also been observed in ET (Louis, 2010a).
2