These two tremor components were identified by measuring the tremor of ET patients once with no weights on their hands and then with 1-lb weights on their hands. The addition of the weights resulted in a tremor spectrum with two peaks, one that maintained the same frequency (the central tremor) and one that decreased in frequency (the peripheral tremor). Only with the addition of the weights was the peripheral tremor distinguishable from the central tremor.The frequency of essential tremor is 4 to 11 Hz, depending on which body segment is affected. Proximal segments are affected at lower frequencies, and distal segments are affected at higher frequencies

Cause
Genetic
The underlying cause of essential tremor is not clear, but many cases seem to be familial. About half of the cases are due to a genetic mutation and the pattern of inheritance is most consistent with autosomal dominant transmission. No genes have been identified yet, but genetic linkage has been established with several chromosomal regions. Toxins
Some environmental factors, including toxins, are also under active investigation, as they may play a role in the diseases cause. Pathophysiology
In terms of pathophysiology, clinical, physiological and imaging studies point to an involvement of the cerebellum and/or cerebellothalamocortical circuits. Changes in the cerebellum could also be mediated by alcoholic beverage consumption. Purkinje cells are especially susceptible to ethanol excitotoxicity. Impairment of Purkinje synapses is a component of cerebellar degradation that could underlie essential tremor. Some cases have Lewy bodies in the locus ceruleus.
Essential tremor (ET), also called benign tremor, familial tremor, and idiopathic tremor, is a medical condition characterized by involuntary rhythmic contractions and relaxations (oscillations or twitching movements) of certain muscle groups in one or more body parts of unknown cause. It is typically symmetrical, and affects the arms, hands, or fingers; but sometimes involves the head, vocal cords, or other body parts. Essential tremor is either an action (intention) tremor—it intensifies when one tries to use the affected muscles during voluntary movements such as eating and writing—or it is a postural tremor, present with sustained muscle tone. This means that it is distinct from a resting tremor, such as that caused by Parkinsons disease, which is not correlated with movement.Essential tremor is a progressive neurological disorder, and the most common movement disorder. Its onset is usually after age 40, but it can occur at any age. The cause is unknown. Diagnosis is by observing the typical pattern of the tremor coupled with the exclusion of known causes of such a tremor. While essential tremor is distinct from Parkinsons disease, which causes a resting tremor, essential tremor is nevertheless sometimes misdiagnosed as Parkinsons disease. Some patients have been found to have both essential tremors and resting tremors.Treatments for essential tremor include medications, typically given sequentially to determine which provides the best compromise between effectiveness and troublesome side effects. Clostridium botulinum toxin (Botox) injections and ultrasound are also sometimes used for cases refractory to medications.