Table 1.

Tremor syndromes based on the predominant manifestation of the tremor (Axis-1).

Tremor category based on activation/position	Tremor subcategories	Key features
Action/rest tremor	Essential tremor	Body parts involved: Bilateral upper extremities involvement for 3-years is mandatory for diagnosis. Voice, head, lower extremities may be involved. Key features: 4–12 Hz action tremor
	Essential tremor plus	Tremor fulfilling the criteria of ET along with additional neurological signs (dystonia, rest tremor, impaired tandem gait)
	Enhanced physiologic tremor	Body parts involved: Bilateral hands and fingers Key features: Low amplitude, high frequency tremor (8–12H z). Can be precipitated or exacerbated by anxiety, caffeine, and hypermetabolic states.
	Isolated action or rest tremor syndromes	Additional clinical features in axis-1 should be explored to reach at the diagnosis. Isolated rest tremor usually affects the upper extremities and may evolve into Parkinson's disease.
Focal tremor	Voice tremor	Body parts involved: Vocal cord, larynx, oropharynx, palate, tongue, lip) Key features: Frequency range 3.8–5.5 Hz
	Head tremor	Body parts involved: Head/neck Key features: Yes-yes or no-no or diagonal direction of tremor, often associated with cervical dystonia or essential tremor
	Palatal tremor	Body part involved: Soft palate (may be associated with myorhythmia in other body parts) Key features: Rhythmic, 0.5–5Hz tremor, may be present during sleep, may be associated with audible clicks
Task specific tremor	Primary writing tremor	Body part involved: Hand used for writing Key features: Tremor only while writing (type-A) or while adopting the hand in writing position (type-B)
	Other tremors in musicians and sports persons	Body part involved: Hand used for the specific task Key features: may be associated with focal dystonia and a compensatory posture
Orthostatic tremor	Primary orthostatic tremor	Body part involved: legs and trunk Key features: 13–18Hz, low amplitude tremor only while standing, associated with subjective unsteadiness
	Pseudo orthostatic tremor	Body part involved: legs Key features: <13 Hz low amplitude tremor, only while standing, associated with subjective unsteadiness
Tremor with additional prominent neurological signs	Re-emergent tremor	Body parts involved: Upper extremities, rarely tongue Key features: Form of postural tremor (3–5 Hz) which emerges after a latency of a few seconds when hands are kept in an anti-gravity posture. Typically present in Parkinson's disease
	Dystonic tremor	Body parts involved: Any of the body parts with dystonia Key features: Irregular, jerky tremor; worsens while resisting dystonic pull and subsides or resolves in maximal dystonic posture (“null point”).
	Holmes' tremor	Body parts involved: Bilateral upper extremity Key features: Present at rest, worsens when holding a posture, intensifies during action
	Myorhythmia	Body parts involved: Cranio-facial and limb muscles Key features: Slow, rhythmic, repetitive movements (1–4 Hz); associated with lesions of the brainstem and/or diencephalic structures
	Wing-beating tremor	Body parts involved: Upper extremities Key features: High amplitude proximal tremor when arms are in abducted position; may be present in Wilson's disease or cerebellar-outflow pathways
Others	Functional tremor	Body parts involved: Any the body part Key features: Abrupt onset, variable in frequency and amplitude, distractible, entrainable; incongruous with organic tremors.