Benign essential tremor syndrome
Essential tremor is a neurological disorder characterized by shaking of hands (and sometimes other parts of the body including the head), evoked by intentional movements. The incidence is unknown, but is estimated to be as common as one person in 20, and it is the most common type of tremor and also the most commonly observed movement disorder. more...
The cause of the disease is unknown (idiopathic). While no identifiable and consistent structural abnormality has been demonstrated yet to exist in the nervous system of every person with ET, prominent researchers including Elan D. Louis are searching actively for neurochemical and brain structure abnormalities that might be commonplace among people with ET. Usually the diagnosis is established on clinical grounds, but when suspicion exists, other potential sources of tremor (excessive caffeine consumption, recreational drug use, hyperthyroidism) should be excluded. Tremor intensity can worsen in response to fatigue, strong emotions, hunger, cold, or other factors and can be reduced with alcohol in approximately 50 percent of patients. However, an over-reliance on alcohol to control tremor symptoms can sometimes lead to alcohol addiction.
There is ongoing controversy as to whether ET is related to Parkinson's disease and whether essential tremor should properly be considered a kind of parkinsonism. While some research findings appear to suggest that ET patients face a greater than average chance of developing Parkinson's, those findings might be a misleading effect of the widespread difficulty that doctors experience when they try to distinguish Parkinson's symptoms from ET symptoms and arrive at a definitive diagnosis.
Members of a family known as the "Iowa Kindred" develop either parkinsonism or symptoms that are indistinguishable from ET; their pattern of inheritance is associated with PARK4.
Essential tremor is often found in more than one member of a family (familial tremor), in which case it is usually dominant in inheritance, or it may occur with no family history. Tremors can start as any age, from birth through advanced ages (senile tremor). Any voluntary muscle in the body may be affected, though it's most commonly seen in the hands and arms and slightly less commonly in the neck (causing the patient's head to shake), eyelids, larynx, tongue, trunk, and legs. A resting tremor of the hands is sometimes present, despite the common misunderstanding that a resting tremor is proof of Parkinson's Disease. ET is usually painless, although in some cases tremor of the head or neck causes pain, and writing can become painful quickly for a person with hand tremors who grips a pen tightly in a struggle to maintain control over penmanship.
ET does sometimes occur in combination with other neurological disorders such as dystonia and benign fasciculation syndrome. However, there is no clear evidence that having ET predisposes a person to one of these diseases. Conflicting research results have so far made it difficult for medical researchers to say with certainty that people with ET are more likely than the general population to experience hearing loss and a reduction or complete loss of olfaction, among a wide assortment of other non-tremor symptoms, but credible researchers have published findings to support such claims of progressive hearing loss and progressive loss of olfaction. Other published research suggests that an impaired sense of balance prevents ET patients from walking normally. It is commonly assumed among researchers that tremors are not the only symptom of ET.
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