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Human beings have been leaving written records about their tremors for thousands of years, with written references to tremor in ancient India, Egypt, Israel, and Greece.1 The hallmark clinical feature of ET is an action tremor (i.e., tremor that occurs during voluntary movement) of the arms, in contrast to a tremor at rest. That physicians were taking care of patients with action and rest tremors is evident in the writings of Galen of Pergamon (130 - 200 A.D.) and much later in those of Sylvius de la Boe(1680), Van Swieten (1745), and Sauvages (1768),1 who each distinguished action from rest tremor. The most complete early account of ET was that of Dr. Charles Dana, the New York neurologist, who in 1887 documented the presence of this tremor in several large families.1,2 Although cases may arise in childhood, most cases of ET are in their 60s or older. The most frequent clinical symptom reported and observed is action tremor. The tremor occurs when the hands are being used actively to perform voluntary activities such as writing, pouring, eating, and other daily activities. Patients with severe ET also have postural tremor, which appears when the arms are held outstretched in front of the body.3 Tremor in ET most commonly affects the arms, but it may also affect the head, voice, and occasionally the trunk and lower extremities.4 Some recent studies have shown postural instability and ataxia (irregular body movements due to defective muscular control), and cognitive abnormalities, specifically, problems with verbal fluency and memory. Even though in the past ET was labeled "benign", we now know that the tremor usually is progressive, producing disabilities with basic daily life activities such as eating, writing, reading, personal care and driving. Severely affected end-stage patients are physically unable to feed or dress themselves. In these, the tremor prevents any normal activity, resulting in a substantial loss of independence and even incapacitation.4 Essential Tremor: Drawing test (left to right: no hand tremor in a healthy control subject without ET, moderate hand tremor in an ET patient, and severe hand tremor in an ETpatient.)
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