Essential tremor is characterized by slow progressive tremors during movement.
Most patients will report tremor that starts from one upper extremity and then affects the other. It is almost always limited to the upper extremities. Tremor is initially intermittent but overtime becomes persistent. The amplitude is worsened by hunger, emotion, fatigue and extremes of temperature. Tremors may also involve the head and face. The tremor is noticed to resolve during sleep and ethanol intake may temporarily reduce its amplitude in up to 70% of cases. There is a family history of tremor in up to 60% of cases. When a tremor is visible, it should be considered pathologic . During physical examination, features of Parkinson disease like rigidity and bradykinesia should be ruled out.
The mortality rate in essential tremor is basically the same as that for the general population. There is however disability from essential tremor with up to 15% of affected individuals being seriously disabled. There is a generally a decreased quality of life primarily due to loss of function.
The cause of essential tremor is still unknown. In absence of any consistently associated pathologic findings, some hypothesis have been promulgated. One of such is the possible involvement of the cerebellar-brainstem-thalamic-cortical circuits. Another is that it is as a result of an abnormally functioning central oscillator that is involves the inferior olivary nucleus. A third hypothesis is that the pathophysiology of essential tremors is diverse.
Some of the factors that have been linked to its etiology include a potent tremor-producing neurotoxin called Harmane and increased glucose consumption in the medulla. There are also multiple etiologies that have been linked with genetics .
The prevalence of essential tremor is about 5.6% of the general United States population, and only about 11% of those affected seek medical attention. The prevalence in the internal community is about 3.9%. It has a bimodal peak age of occurrence, in late adolescence/early adulthood and in the older age group and the mean age of occurrence is between 35 to 45 years. It usually manifests by age 65 years and the amplitude of the tremor increases over time. The race demographic has not been well studied but there appears to be a higher prevalence in Caucasians than in African-Americans. It occurs with equal frequency in both sexes .
Essential tremors are also known as kinetic tremor as they intensify when the muscle groups are put in play . It is the most common movement disorder and it usually affects both upper extremities. The etiology is unknown but there is a debate as to whether or not it is a neurodegenerative disease.