Chapter 29 - Essential Tremor and Other Tremors

Abstract

Tremor is the most common movement disorder encountered in clinical neurology. Although most tremors are pathological, a low-amplitude physiological action tremor can be detected in healthy subjects and may be of functional relevance for normal motor control. The disabilities caused by these tremors are as diverse as their clinical appearance, pathophysiology, and etiologies. The clinical and instrumental features of the tremor syndromes are presented. Essential tremor (ET) is a slowly progressive tremor disorder that sometimes causes severe disability but is not life-limiting. The traditional view of ET as a monosymptomatic disorder has been revised because this disorder is more complex and heterogeneous. The heterogeneity may partly be due to diagnostic uncertainty, with different sets of diagnostic criteria all using only medical history and clinical findings. ET starts with a postural tremor, which can still be suppressed during goal-directed movements. In advanced stages, an intention tremor can develop and is accompanied by signs of cerebellar dysfunction of hand movements, such as movement overshoot and slowness of movements. The features of ET are described in chapter. Hypotheses on the pathophysiology of ET are discussed, which is based on the studies on environmental and genetic factors and on other evidence. An evidence-based review of treatments for ET has confirmed that the first-line pharmacological agents are propranolol, primidone, gabapentin, and topiramate. The chapter discusses the physiological and enhanced physiological tremor, parkinsonian tremors, orthostatic tremor, dystonic tremor, drug-induced and toxic tremors, psychogenic tremors, primary writing tremor, cerebellar tremor syndromes, Holmes' tremor, tremor syndromes in peripheral neuropathy, and palatal tremor syndromes. The rare (or undetermined) tremor syndromes are also discussed, such as hereditary chin tremor, fragile X–associated tremor/ataxia syndrome, bilateral high-frequency synchronous discharges, microsaccadic oscillations and limb tremor, isolated tongue tremor, tremor induced by peripheral nerve injury, and rhythmic myoclonus.