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Tremor is an involuntary, rhythmic, and oscillatory movement of a body part.

It is caused by either alternating or synchronous contractions of antagonistic muscles: ones that pull against each other. Tremor is the most common of all movement disorders, occurring from time to time in many normal individuals in the form of exaggerated physiological tremor.

What is a Tremor?

Tremor is the medical term for trembling or shaking. A person with a tremor has a body part that shakes, and the person cannot control the shaking. Most often this shaking affects the hands or the head, but other body parts can be affected, too. The tremor can be a problem on its own, or it can be a caused by another health problem.

There are several different types of tremors:
  • Rest tremors – Rest tremors happen while sitting or lying down and relaxed. People who have a rest tremor can usually stop the tremor by making a point of moving the part of their body that shakes.
  • Action tremors – Action tremors occur when moving muscles on purpose. There are a few different kinds of action tremors, including the following:
    • Kinetic tremors – These happen when moving on purpose, such as writing or drinking from a cup. Sometimes, the tremor gets worse gradually when moving closer to an object or when reaching. This is called “intention” tremor.
    • Postural tremors – These appear when holding a body part still in a position other than its resting position. For example, legs might shake when standing up, or arms might shake if held out in front.
    • Isometric tremors – These occur when moving a muscle against something that is still. For instance, they might happen when pushing against a wall or making a fist.
  • Functional tremor – Functional tremor can combine features of rest and action tremors. Unlike other kinds of tremor, functional tremor has no known medical cause and is a manifestation of a psychological condition.

What are the Most Common Causes of Rest Tremor?

The most common cause of a rest tremor is Parkinson’s Disease or its variants. Other potential etiologies for rest tremor include:

  • Rubral tremor, caused by conditions that damage part of the brainstem.
  • Dystonia, a neurological disease, causing twisting movements and abnormal postures.
  • Wilson disease, a rare inherited disease that causes copper build up in the body.

What Are the Most Common Causes of Action Tremor?

The most common cause of action tremor is something called a “physiologic” tremor. Everyone, even people who are healthy, has a little bit of shaking of the hands. This is “physiologic tremor.” It is normal and not usually noticed it because it is so mild. In some cases, this “physiologic” or normal tremor can be more prominent. Examples of when this can occur include the following:

  • With certain medications, such as those used to treat depression, asthma, or other breathing problems.
  • Drinking coffee or other caffeinated beverages.
  • Smoking cigarettes.
  • Being anxious, excited, or afraid.
  • If muscles are very tired, for example because of just working out.
  • Effects of alcohol or other drugs when wearing off.
  • Fever.

If tremor is caused by one of the problems listed above, the tremor goes away as soon as the problem resolves. Of course, if tremor is caused by a medication, stopping it may not be reasonable, but switching to a similar medication or to a lower dosage may be. Other possible causes of action tremors may include:

  • Cerebellar tremor, caused by damage to a part of the brain called the cerebellum or the pathways that connect to it. Patient with multiple sclerosis, brainstem trauma, and stroke may experience this type of tremor.
  • Primary writing tremor, which occurs exclusively while writing and never during other voluntary movements.
  • Orthostatic tremor, which is limited to the legs and appears only while standing.

Diagnostic Testing/Work-up for Tremor

There is not one specific test to diagnose tremor; however, the physician and healthcare team can learn a lot about tremor through physical examination, observation, and asking questions. Imaging studies and blood tests may also be ordered to ensure tremor is not caused by something else. To best determine the type of tremor and what might be causing it, questions that may be asked include:

  • Does the tremor happen when resting, when sitting still, when holding the arms out, or when moving?
  • Are there activities or circumstances that make the tremor better or worse?
  • Which body parts are affected?
  • Are the left and right side equally affected by the tremor?
  • When did the tremor start? Did the start time coincide with any other symptoms, starting new medications, or any injuries or illnesses?
  • Does drinking alcohol affect the severity of the tremor?

The Mayo Clinic, The National Institutes of Health, UptoDate.com