Essential tremor

The causes of essential tremor are unknown. Researchers are studying several areas (loci) on particular chromosomes that may be linked to essential tremor, but no specific genetic associations have been confirmed. Several genes, as well as environmental factors, are likely involved in an individual's risk of developing this complex condition.

Essential tremor is a disorder of the nervous system that causes involuntary, rhythmic shaking (tremor). The signs and symptoms of essential tremor often worsen over time, but symptoms can vary greatly from person to person. While it most often affects the hands and arms (one or both), it can also affect the head, voice, chin, legs, and trunk. A recent study reported the following rate of clinical exam findings of tremor in people with essential tremor:

Upper extremities (97%)
Voice (62%)
Head or neck (48%)
Lower extremities (9%)
Chin (9%)
Trunk (4%)

Head tremor typically occurs along with other tremor, such as of the hand or voice. Rarely (in severe cases) essential tremor may mildly affect walking and mental proccessing. Factors triggering tremor can vary between people with essential tremor.

About half of all cases of essential tremor appear to occur because of a genetic mutation. This is referred to as familial tremor. In these cases, essential tremor appears to be passed through generations in families, but the inheritance pattern varies. In many affected families, the condition appears to be inherited in an autosomal dominant manner, which means one copy of an altered gene in each cell is sufficient to cause the disorder. In other families, the inheritance pattern is unclear. Essential tremor may also appear in people with no history of the disorder in their family.

In some families, there are individuals who have essential tremor while others have other movement disorders, such as involuntary muscle tensing (dystonia). The potential genetic connection between essential tremor and other movement disorders is an active area of research.

While not rare, the most common differential diagnosis for essential tremor is parkinsonian tremor. Distinguishing Parkinson disease from essential tremor can be difficult due to overlap in signs and symptoms. In essential tremor, head tremor rarely occurs alone, but when it does cervical dystonia should be ruled out. Likewise, if voice tremor occurs alone (which is rare), spasmodic dysphonia should be ruled out.

Several studies have demonstrated that essential tremor may be associated with hearing impairment, although the basis for the association is not clear. The age of onset of essential tremor has been shown to be significantly higher in those who have reported hearing impairment. A thorough search of available resources does not yield any specific information about affected individuals reporting muffled sounds or increased pressure in the ears.

Although essential tremor is not life-threatening, it can make it harder to perform daily tasks and is embarrassing to some people. Hand tremor is most common but the head, arms, voice, tongue, legs, and trunk may also be involved. Although it may be mild and nonprogressive in some people, in others the tremor is slowly progressive, starting on one side of the body but eventually affecting both sides. Tremor frequency may decrease as a person ages, but the severity may increase, affecting the person's ability to perform certain tasks or activities of daily living. In many people the tremor may be mild throughout life.

If severe, essential tremor may interfere with fine motor skills used to do simple tasks like holding eating utensils, drinking a glass of water, tying shoelaces, writing, sewing, shaving, or applying makeup. Sometimes the tremors affect the voicebox, which occasionally leads to speech problems.

The symptoms of essential tremor may be aggravated by emotional stress, fever, fatigue, hunger (low blood sugar), caffeine, cigarette smoking, or extremes of temperature.

Essential tremor is the most common movement disorder. It is characterized by involuntary and rhythmic shaking (tremor), especially in the hands, without any other signs or symptoms. It is distinguished from tremor that results from other disorders or known causes, such as tremors seen with Parkinson disease or head trauma. Most cases of essential tremor are hereditary. There are five forms of essential tremor that are based on different genetic causes. Several genes as well as lifestyle and environmental factors likely play a role in a person's risk of developing this complex condition. In mild cases, treatment may not be necessary. In cases where symptoms interfere with daily living, medications may help to relieve symptoms.

Treatment for essential tremor may not be necessary unless the tremors interfere with daily activities or cause embarrassment. Although there is no definitive cure for essential tremor, medicines may help relieve symptoms. How well medicines work depend on the individual patient. Two medications used to treat tremors include:

• Propranolol, a drug that blocks the action of stimulating substances called neurotransmitters, particularly those related to adrenaline
• Primidone, an antiseizure drug that also control the function of some neurotransmitters

These drugs can have significant side effects.

Eliminating tremor "triggers" such as caffeine and other stimulants from the diet is often recommended. Physical therapy may help to reduce tremor and improve coordination and muscle control for some patients.

More details about the management of essential tremor can be accessed through the Mayo Clinic and Medscape.