Dystonic tremor

Tremor is the most common movement disorder, known since the time of Galen, and defined as a rhythmic involuntary movement of one or several regions of the body (Albanese and Jankovic 2012). Many attempts have been made in the last century to define and classify normal and pathological tremors, but a comprehensive summary did not exist until the Movement Disorder Society developed a first consensus statement (Deuschl et al. 1998). Among several types of tremor, essential tremor (ET) is the most common, although its epidemiology is still unclear (see also Chap. 10 ). The clinical signs and symptoms of ET are much broader than previously thought, ranging from a relatively benign postural tremor to a disabling kinetic or intention tremor that affects the hands and also the head (Leegwater-Kim et al. 2006). Even rest tremor has been observed in advanced ET. A tremor similar to ET may occur in dystonia and can be mistaken for non-dystonic tremor, particularly when it is isolated (Lalli and Albanese 2010). Various types of focal task-specific tremors (e.g., vocal tremor, primary writing tremor) have been described in the past 35 years and it is still a matter of debate whether these tremors are focal tremulous dystonias, focal essential tremors, or an independent condition.