Tremor is the most common movement disorder in adults. Causes can be roughly divided into neurological (for example: Parkinson’s disease, essential tremor ), metabolic (e.g. hyperthyroidism (increased thyroid activity) or hypoglycemia (decreased glucose level), functional and tremor due to drugs.  Medicines are probably the most common cause of tremor.  Many medications have a tremor as a side effect. These are drugs that are used in both psychiatry and somatic diseases (e.g., lithium, valproic acid, salbutamol, theophylline).

Definition

Tremor has been defined in a  consensus discussion  as an involuntary, rhythmic, oscillating movement of any part of the body1. Its rhythmic aspect is very characteristic and distinguishes it from many other movement disorders such as dyskinesia, dystonia, or myoclonus.

Introduction

A basic classification is tremor at rest and tremor with activity.

At rest does not mean during sleep because then the tremor usually has disappeared, but when the body part is fully supported against gravity. For example, if you sit with your arms on the chair back. This is called the resting tremor.

An action tremor is present when you adopt a certain position or move a body part. An action tremor is further divided into kinetic tremor, postural tremor, and intention tremor.

A kinetic tremor occurs when performing a movement, for example grabbing a cup.

A postural tremor occurs when the affected body part is held against gravity in a certain position (for example outstretched arms).

An intention tremor is characterized by a shocking movement when approaching the target. This can be tested with the finger-to-nose (with closed eyes, let the finger go to the nose in a wide arc, alternating left and right finger).

Tremor due to drugs

In the article by Morgan et al. there are several tables that help with diagnostics 2.  If you suspect a tremor due to a drug, you can ask the following questions.

  1. Has the tremor been described as a side effect of the drug?
  2. Did the tremor exist before the drug was given?
    A physiological tremor is often missed and sometimes the drug intensifies a pre-existing tremor.
  3. Could there be another cause?
    a. Hyperthyroidism, hypoglycemia, a neurological disease, or a functional tremor?
  4. Is there a time relationship: did the tremor start after starting the drug or increasing the dose?Is there a dose relationship?
    a. Typical for a tremor increase is when drug dose is increased.
  5. Has it increased over time??
    a. Usually a tremor caused by a drug remains constant in severity. A tremor in Parkinson’s disease or essential tremor is often progressive.

Examination of a tremor

  1. Observation and questioning daily activities.
    a. Common questions are, eating soup, key in lock, pins, feelings of embarrassment, do other body parts have tremor, (e.g., head, legs, chin, tongue).
  2. Stretch hands out horizontally with fingers spread.
    a. This makes the postural tremor clearly visible. Place a piece of paper on top of the hands and the tremor becomes even more visible.
  3. Change in tremor with activity and/or walking.
    a. Often a tremor increases when walking.
  4. Finger-to-nose test
    a. To test the intention tremor
  5. Have the Archimedes’ spiral drawn, and a sentence written.
    a. A standard test that often reveals the tremor.
  6. Pour a cup of water into another cup.
    a. Separate cups from each other (sometimes keep a towel ready).
  7. Entrainment test
    a. A test for functional tremor: Ask a patient to make voluntary movements at a specified frequency with the unaffected limb. On the side where the functional tremor is located, the frequency and/or severity of the tremor often changes.
  8. Holding the limb with the tremor
    a. A tremor has little force and can be easily stopped by the researcher. You will feel the tremor frequency in your hand, but the amplitude is considerably reduced by the counter pressure. With functional tremor, the tremor can push through it, as it were.
  9. Laboratory (Thyroxine, glucose, and possibly other lab determinations),
  10. Studymytremor
    a. A very handy app.

Movies

A poignant picture of patients with essential tremor

Parkinson tremor

Entrainment test

Literature

1. Bhatia KP, Bain P, Bajaj N, et al. Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord 2018; 33(1): 75-87.

2. Morgan JC, Kurek JA, Davis JL, Sethi KD. Insights into Pathophysiology from Medication-induced Tremor. Tremor and other hyperkinetic movements 2017; 7: 442.