There are a large number of neurological disorders, all with different causes and which can produce a great many symptoms, depending on the area or areas they affect. Some of them are linked to the control of movement. Among these, Parkinson’s disease is particularly well known, but there are many problems with similar symptoms.

One of them, which is often confused with the previous disease and which is very common, is the essential tremor .

Essential tremor: characteristics and symptoms

Essential tremor is a very frequent neurological disorder in the population, especially in those over 65 years of age, characterized by the presence of involuntary and persistent tremors or rhythmic shaking. These tremors occur especially in the hands and arms, generally in both extremities at the same time and in a symmetrical manner. It is also common for tremors to appear in the face, and may also affect the voice. Although not as frequent, sometimes the same occurs in the legs.

These tremors occur when the subject is making voluntary movements or maintaining certain postures, such as when extending arms, eating, writing or driving. Such tremors can vary in intensity according to the moment, and without treatment can worsen with age .

As a general rule and unless it overlaps with other disorders (it may appear in conjunction with diseases such as Parkinson’s), essential tremor is confined to the motor domain only. In other words, essential tremor per se does not cause cognitive impairment or other disorders . It is not a dementia or a neurodegenerative disease.

Although the main symptoms are the aforementioned tremors (although sometimes fatigue and weight loss may occur) when performing actions or maintaining postures, and it does not cause mental deterioration, this disease can become very disabling in different aspects of life.

For example, actions that require precision such as sewing or even drinking from a glass can be very complicated. Not surprisingly, sufferers may also have some depressive symptoms. Some people may have to quit their job (for example, a surgeon) or seek alternative methods of travel (driving is extremely dangerous).

This disease usually appears between the ages of 40 and 65. Despite this, cases have been detected at all ages, and may even appear in childhood .

Causes of the disorder

In this disorder there are alterations in the nerve connections of the different nuclei that regulate movement , such as the cerebellum, thalamus or the nigrostriatal pathway. However, the causes of these alterations are currently not fully known.

The data and evidence reflect that there is a genetic origin in a high percentage of cases. In several families mutations have been located in the D3 receptor gene , but this does not occur in all cases. The genes involved vary from study to study. But there is also an environmental influence, as there are also sporadic cases in which there is no genetic inheritance.

Similarities and Differences with Parkinson’s

It has been noted above that this disease is often confused with Parkinson’s for a variety of reasons . The causes of this confusion are based on the similarity of its symptomatology and some neurological characteristics. In addition, in some cases people with essential tremor have a predisposition to Parkinson’s, which they may or may not develop.

In both cases we found the presence of involuntary tremors. However, while in Parkinson’s disease, the tremors at rest stand out, in essential tremor the tremors occur when the subject is performing a movement or maintaining a posture.

Another common aspect is that in Parkinson’s disease the nigrostriatal pathway is greatly affected, with problems in the transmission of the neurotransmitter dopamine. In essential tremor there may also be an affectation, degeneration or hypofunction of this pathway, although it is not essential.

In Parkinson’s, however, the presence of so-called Lewy bodies can be seen in the pathway. In many of the studies carried out so far they are not present in essential tremor, although in recent literature cases have been found in which they were also present, usually in cases with a predisposition to Parkinson’s. In other cases they have been found in the cerebellum.

It also highlights the fact that with respect to pharmacological treatment , substances that are useful in one disorder often have no effect on the other. For example, L-dopa used in Parkinson’s disease is not usually helpful in essential tremor. There are exceptions such as some surgeries and drugs such as zonisamide, which in many cases is beneficial for both conditions.

Common treatments for essential tremor

Essential tremor is a disease that does not currently have a curative treatment , but treatments are aimed at reducing the tremors present in it and improving the quality of life of the patient.

Essential tremor is often made worse by the consumption of some exciting substances such as coffee, which is why this substance is often contraindicated. Alcohol in small doses may produce some decrease in tremor, but caution should be exercised with doses and may worsen the tremor over time. It has been observed that tremors may be less when movements are performed using elements that have a certain weight.

At the level of drug treatment, different substances such as primidone (an anticonvulsant) or beta-blockers such as propranolol are often used. Sometimes antidepressants and anxiolytics are also used. The choice of the drug in question will depend on the patient’s characteristics or possible side and/or adverse effects (e.g. propanolol lowers blood pressure).

Another treatment used is the injections of botulinum toxin or botox , especially in areas such as the hands or head, which decrease the intensity of the tremors.

When tremors are severe or very disabling, surgery may also be used. In this sense, deep brain stimulation is usually used, in which a device is installed that stimulates different points of the brain with electrical impulses in a similar way to a pacemaker, or repetitive transcranial magnetic stimulation. In the most serious cases, part of the thalamus can also be excised.

Bibliographic references:

  • Bermejo, P.E.; Ruiz-Huete, C. and Terrón, C. (2007). Relationship between essential tremor, Parkinson’s disease and dementia with Lewy bodies. Rev. Neurol. 45; 689-694.
  • Labiano-Fontcuberta, A and Benito-León J. (2012) Temblor esencial: una actualización. Medicina Clinica, 140 (3). 128-133.
  • Lucotte, G.; Lagarde, J.P.; Funalot, B. & Sokoloff, P (2006). Linkage with the Ser9Gly DRD3 polymorphism in essential tremor families. Clin Genet; 69: 437-40.
  • Schuurman, P.R.; Bosch, D.A.; Bossuyt, P.M.M. et al (2000).. Una comparación de la estimulación talámica continua y la talamotomía para la supresión de un temblor severo. N Engl J Med.;342:461-468.