Essential Tremor and Other Forms of Kinetic Tremor

Kinetic tremor is a tremor (i.e., a rhythmic and oscillatory movement) that occurs during guided voluntary movements like writing or touching finger to nose. As such, it is a type of action tremor, that is, tremor that occurs during the voluntary contraction of skeletal muscle. It may be distinguished from rest tremor, which occurs when a limb is fully relaxed, and intention tremor, which is present with visually guided movement and increases in amplitude with the approach of the target. A broad range of kinetic tremors occurs and these may be divided into those that are normal vs. pathological. Physiological or enhanced physiological tremor is the most common form of normal tremor (Elble, Mov Disord 13 Suppl 3:35–39, 1998a; Elble, Mov Disord 13(3):457–464, 1998b; Elble, Clin Neurophysiol 114(4):624–635, 2003; Louis et al., Arch Neurol 55(2):222–227, 1998a; Louis et al., Mov Disord 13(5):803–808, 1998b; Louis et al. Mov Disord 13(1):5–10, 1998c) and essential tremor (ET) is the most common pathological form of tremor (Louis and Ferreira, Mov Disord 25(5):534–541, 2010; Louis and McCreary, Tremor Other Hyperkinet Mov (N Y) 11:28, 2021). Other pathological tremors include dystonic tremor, orthostatic tremor, drug-induced tremor, and several other conditions. The focus of this chapter is the pathological forms of kinetic tremor, and we will begin with ET, which is the most common of these.