Other Tremor Disorders
EPT has the same frequency characteristics as physiologic tremor but is easily visible and is mainly postural. The diagnosis not made if there is an underlying neurological pathology. Screening for potential metabolic derangements associated with tremor should be performed. The distinction between EPT and mild forms of ET is ambiguous and somewhat arbitrary, and is usually based on the presence and extent of functional disability with the latter.
Primary Orthostatic Tremor is a unique syndrome, characterized by the presence of high frequency (13-18Hz) tremor of the trunk and legs that occurs only with stance (Britton, 1995). In other words, patients are asymptomatic when lying or sitting. Symptoms rarely persist with walking. Yet, subjectively, patients report feeling unsteady when standing up. Constant change of position of the feet relieves the symptoms. Patients quickly learn to march in one spot. The clinical exam is benign but for minimally visible and sometimes only palpable fine amplitude rippling of the leg muscles. The diagnosis can be confirmed by the electromyography of the quadriceps muscles, which records a typical 13-18 Hz tremor pattern. Symptoms respond to low dose clonazepam.
This is a group of tremor syndromes that shares the common feature of tremor activation when engaged in a specific task. The most common type is primary writing tremor, in which symptoms appear only or predominantly with that particular activity. Use of the limb with other activities (eating, weight-lifting, etc.) does not produce tremor. Other examples include task-specific tremors of musicians and athletes, as well as isolated voice tremor. In some of these cases, patients have dystonic posturing of the limb in conjunction with tremor, or focal dystonia with dystonic tremor.
Relevant Links: Essential Tremor and Other Tremor Disorders