Essential Tremor and Other Tremor Disorders
Tremor is the most common type of all movement disorders, the incidence of which increases with age, independent of etiology. Considering that tremor can be a manifestation of a variety of neurological conditions, prevalence data is available only in respect to the most common diagnostic entities, specifically, essential tremor (ET), which is a monosymptomatic disorder with no neurological signs other than postural/action tremor, and parkinsonian (PD) tremor. Reported ET prevalence varies from 0.0005 to 5.5%, depending on the study methodology and the population age. Despite such a wide range, there is unanimous agreement among investigators of increasing prevalence of ET with age.
Despite the high prevalence of tremor, knowledge of its pathophysiology and anatomic generators is limited. Central versus peripheral nervous system origin of tremor is debated. It remains unclear if tremor generators are disease- specific or if there is a common final pathway independent of tremor etiology.
There are multiple potential causes of tremor. From the clinical standpoint, physicians define the tremor syndrome, which will guide in the choice of therapeutic intervention.
Tremor is present in the joint or muscle that is free to oscillate. It has a low amplitude and high frequency. Usually it is not visible, except for intermittent finger tremor.