Criteria

Movement Disorder Society on tremors[4]

Essential tremor (ET):

  1. Isolated tremor syndrome of bilateral upper limb action tremor

  2. At least 3 years’ duration

  3. With or without tremor in other locations (e.g., head, voice, or lower limbs)

  4. Absence of other neurological signs, such as dystonia, ataxia, or parkinsonism.

Essential tremor plus:

  • Tremor with the characteristics of ET and additional neurological signs of uncertain significance such as impaired tandem gait, questionable dystonic posturing, memory impairment, or other mild neurological signs of unknown significance that do not suffice to make an additional syndrome classification or diagnosis.

  • ET with tremor at rest should be classified here.

Exclusion criteria for ET and ET plus:

  • Isolated focal tremors (voice, head)

  • Orthostatic tremor with a frequency >12 Hz

  • Task- and position-specific tremors

  • Sudden onset and stepwise deterioration.

Washington Heights-Inwood Genetic Study of ET criteria[81]

Tremor severity scale:

  • 0 = no visible tremor

  • +1 = low-amplitude tremor, barely perceivable or intermittent

  • +2 = moderate-amplitude tremor, usually present and clearly oscillatory

  • +3 = large-amplitude, violent, jerky tremor.

ET inclusion criteria

  • On examination, a +2 postural tremor of at least one arm (a head tremor may also be present, but is not sufficient for the diagnosis).

  • On examination, there must be a +2 kinetic tremor during at least four tasks, or a +2 kinetic tremor on one task and a +3 kinetic tremor on a second task. Tasks include pouring water, using a spoon to drink water, drinking water, finger-to-nose manoeuvre, and drawing spirals.

  • If on examination the tremor is present in the dominant hand, then by report it must interfere with at least one activity of daily living (e.g., eating, drinking and writing, using the hands). If on examination the tremor is not present in the dominant hand, then this criterion is irrelevant.

  • Medicines, hyperthyroidism, ethanol, or dystonia are not potential aetiological factors.

  • No psychogenic features (e.g., bizarre features, inconsistent in character, patient is distractable, other psychiatric features on examination).

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