Tremor was defined in 1914 by Jules DEJERINE as an "involuntary rhythmic oscillation affecting all or part of the body around its position of equilibrium". This neurological and genetic disease can appear from an early age; it is more common in adults, and affects both men and women. Essential tremor is a pathology caused by dysfunction of the brain circuits involving the cerebellum, the deep structures and the cortex that control the muscles.
The tremors are generally located in the muscles of the upper limbs, in posture (holding a glass) or in action (drinking a cup of coffee). In a 2nd stage, these tremors can affect the neck (head tremor) and the voice (croaky voice).
The simplest gestures, such as writing, typing on a keyboard or pouring a cup of coffee, become real challenges, making daily life difficult.
Essential tremor is the most common form of tremor, three times more common than Parkinson's disease in people over 65. It is defined as:
- It is a tremor of attitude and action, unlike the tremor observed in Parkinson's disease, which is a tremor of rest.
- It affects both sides of the body (bilateral)
- It is not associated with other neurological symptoms
- It often runs in families
What causes essential tremor?
Essential tremor is genetic in 50-70% of cases. Familial cases are autosomal dominant. For sporadic, non-familial cases, the hypothesis of a multifactorial disease with a genetic predisposition and environmental factors has been put forward. However, the many genetic studies currently underway have not identified the genes responsible.
How is essential tremor diagnosed and what is its course?
Essential tremor is diagnosed clinically on the basis of the characteristics of the type of tremor, its impact on daily life, its course and its personal and family history. The clinical examination helps to rule out other causes of tremor, such as the side effects of certain drugs, thyroid disease or Parkinson's disease, and to remove the social stigma of alcoholism.
An international consensus has been reached on the diagnosis of essential tremor: the tremor affects the upper limbs first, is bilateral, and occurs during action (writing, drinking) and posture (holding hands out in front of the body, placing index fingers face to face (sign of the swordsman). The neck and voice may be affected by tremor over time; there is no tremor at rest.
How is essential tremor treated?
There is no specific treatment capable of completely eliminating tremor. Beta-blockers, anti-epileptics or anxiolytics may be prescribed, but these only partially reduce the symptoms. For some years now, deep brain stimulation has been used in patients suffering from severe forms of essential tremor, reducing the intensity of the tremors by up to 80%. At the Institut du Cerveau, neuromodulation therapy (focused ultrasound) is the subject of a clinical research trial.