The activation condition should be described as resting, kinetic (or intention), postural, or isometric. The first step is to categorize the tremor based on its activation condition, topographic distribution, and frequency. 17 Although there is overlap and variability among tremor syndromes, the intrinsic features of the tremor usually provide key diagnostic clues ( Figure 1 18 Table 4 18).
The diagnosis of tremor is generally based on clinical information obtained from the history and physical examination. If there is diagnostic uncertainty, single-photon emission computed tomography can be used to visualize the integrity of the dopaminergic pathways in the brain, and transcranial ultrasonography may be useful to diagnose Parkinson disease.
This tremor is typically unilateral, occurs at rest, and becomes less prominent with voluntary movement. More than 70% of patients with Parkinson disease have tremor as the presenting feature. In one-half of cases, it is transmitted in an autosomal-dominant fashion. The most common pathologic tremor is essential tremor, which affects 0.4% to 6% of the population. Action tremors occur with voluntary contraction of a muscle and can be further subdivided into postural, isometric, and kinetic tremors. Resting tremors occur in a body part that is relaxed and completely supported against gravity. The first step in evaluating a patient with tremor is to categorize the tremor based on its activation condition, topographic distribution, and frequency. Other types of tremor include cerebellar, dystonic, and drug- or metabolic-induced. Features consistent with psychogenic tremor are abrupt onset, spontaneous remission, changing tremor characteristics, and extinction with distraction.
All persons have low-amplitude, high-frequency physiologic tremors at rest and during action that are not reported as symptomatic, but can be enhanced by anxiety, medication use, caffeine intake, or fatigue. The most common tremors in patients presenting to primary care physicians are enhanced physiologic tremor, essential tremor, and parkinsonian tremor. The diagnosis of tremor is based on clinical information obtained from the history and physical examination. It is the most common movement disorder encountered in primary care. Tremor is an involuntary, rhythmic, oscillatory movement of a body part.
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