tremor
Meaning of tremor: When the shaking appears matters far more than how bad it looks, because timing points to which part of the motor system is failing.
Definition of tremor
A tremor is an involuntary rhythmic shaking of a part of the body, produced by muscles contracting and relaxing in a repeating cycle. It most often affects the hands, though the head, voice, jaw, trunk or legs can shake instead. Tremors are grouped by when they appear: at rest, while holding a position against gravity, or during a deliberate movement.
Why does the timing matter?
Every muscle is under constant small correction, so a faint shaking exists in everyone and shows up when the hands are held out. A tremor becomes a finding when it grows large enough to be seen or to interfere with a task. The circumstance that brings it out says more than its size does, because different parts of the motor system fail under different conditions, and this grouping is the first question asked at any assessment.
| When it appears | Name | Typical setting |
|---|---|---|
| At rest, fading on movement | Rest tremor | Parkinson disease |
| Holding the arms out | Postural tremor | Essential tremor, overactive thyroid, drug effects |
| Reaching a target, worst near it | Intention tremor | Damage to the cerebellum, including multiple sclerosis |
What causes it besides brain disease?
Plenty of shaking has nothing to do with degeneration of the brain. Caffeine, nicotine, tiredness, hunger, cold and fear all exaggerate the tremor everyone already has. An overactive thyroid does the same continuously, so a fine fast shake of the outstretched hands is a recognized sign of hyperthyroidism alongside weight loss and a fast pulse. Withdrawal from alcohol produces a coarser tremor with sweating and agitation. Many prescribed medicines cause one, among them inhalers that open the airways, lithium, valproate and antidepressants such as sertraline. A tremor that began when a drug began, and that affects both hands equally, is usually explained by the drug.
How is essential tremor told apart from Parkinson disease?
| Feature | Essential tremor | Parkinson tremor |
|---|---|---|
| When it appears | Holding a posture or acting | At rest, easing on movement |
| Parts affected | Both hands, often head and voice | Usually one hand first |
| Effect of alcohol | Often briefly reduced | Little change |
| Other signs | None | Slowness, stiffness, small handwriting |
The two conditions confused most often are separated less by the shaking itself than by everything around it. Essential tremor tends to run in families and to build gradually over decades, while a rest tremor arriving on one side with slowness and stiffness suggests Parkinson disease. Both can occur in the same person, which is part of why the distinction takes time to settle.
Also known as
Used in a sentence
A fine tremor of the outstretched hands was noted on examination.
Good to know
A tremor present at rest that eases as the limb moves points toward Parkinson disease, while one appearing only on holding a posture or acting is more typical of essential tremor, and an overactive thyroid, alcohol withdrawal and several common medicines produce a similar action tremor.
Word origin
Where “tremor” comes from
Tremor is the Latin word for a trembling, from the verb tremere, meaning to shake or quiver.