A tremor was defined in 1914 by Jules Dejerine as ‘a rhythmic and involuntary oscillation affecting all or part of the body around its equilibrium position’. This genetic neurological disease can appear from a young age, but is more common in adulthood, and equally common in men and women. Essential tremor is a condition caused by a malfunction in the brain circuits involving the cerebellum, the deep structures of the brain and the cortex, which together control muscles.
Tremors generally occur in the muscles of the upper limbs, in the posture (holding a glass) or an action (drinking a cup of coffee). In a 2nd stage, these tremors can affect the neck (head tremors) and the voice (quivering voice).
The simplest actions, like writing, typing on a keyboard or pouring a cup of coffee, become significant challenges and make daily life difficult.
Essential tremor is the most common form of tremor. It is three times more common than Parkinson’s disease in people aged over 65. It is defined as:
- An action or kinetic tremor, unlike the tremors seen in Parkinson’s disease, which are resting tremors.
- It affects both sides of the body (bilateral)
- It is not associated with other neurological symptoms.
- It is often familial
Causes of essential tremor
In 50 to 70% of cases, essential tremor has a genetic origin. It has autosomal dominant transmission for familial cases. For sporadic, non-familial cases of essential tremor, it is a multifactorial disease that combines a genetic predisposition with environmental factors. However, the high number of genetic research projects under way has not succeeded in formally identifying the genes responsible.
Essential tremor diagnosis and evolution
A clinician will diagnose essential tremor based on the characteristics of the tremor, its impact on daily life, its evolution and the patient’s personal and family history. Clinical examination will rule out other causes of tremor, such as side effects from certain medicines, thyroid disease, Parkinson’s disease and the effects of alcohol withdrawal and its associated social stigma.
There is international consensus around the diagnosis of essential tremor: the tremor is observed as first affecting the upper limbs, it is bilateral, it occurs during an action (writing, drinking) and then in postures. The latter is tested by the patient extending their hands in front of them, with index fingers facing each other, and holding this pose. The neck and voice can be affected by tremors over time, and there is no resting tremor.
Treatments for essential tremor
There is no specific treatment able to completely eliminate tremor. Beta blockers, anti-epileptics or anxiolytics may be prescribed, but only partially reduce symptoms. Deep brain stimulation has been used for several years in patients suffering from severe forms of essential tremor, reducing the intensity of tremors by up to 80%. At Paris Brain Institute, we are conducting a clinical research trial into neuromodulation therapy (focused ultrasound).