These are involuntary movements characterized by the repetitive and oscillating action of any part of the body. This can typically be seen in hands at rest, as in Parkinson's, or when carrying out certain actions with one’s hands, as in essential tremor. We can also see tremors in the head or vocal cords translated clinically in a trembling voice.

This will depend on the type of tremor. In the case of essential tremor, this can be seen from the fifth or sixth decade of life onward and is not usually seen in children. The tremors that accompany degenerative diseases can occur at any age.

Not all tremors are part of Parkinson's disease. Patients with thyroid problems may also have tremors and patients with MS often have them.

The cause of essential tremor is unknown. There is evidence to believe that there is a genetic disorder, it is called hyper-function of the red nucleus of the brainstem, which leads to a high production of adrenalin. Brain trauma, when affecting the connections between cerebellum and pale nuclei, causes disabling tremors. Sclerotic plaques in the brain stem of patients with multiple sclerosis can cause tremors in the limbs.

Patients affected by essential tremor usually do not worsen over the years, that is, the condition is static in time and the degree of disability does not depend on aging. The same goes for traumatic causes. In multiple sclerosis severity will depend on where the sclerotic plaques are located. Tremors in Parkinson's usually fade over the years to give way to more serious complications and greater rigidity and slowness.