Causes of Resting Tremor in Parkinson's Disease

Resting tremor. Getty Images Credit: PeopleImages

For three out of every four people who develop Parkinson’s disease (PD), the disease begins with a trembling or shaking in one of the hands. It can also appear on the feet, face, or jaw but usually, it appears in one of the hands. This tremor happens when the muscles of the hands are relaxed and at rest. Hence the name: resting tremor.

Tremor Has a 'Pill-Rolling' Quality

The tremor usually looks like you are rolling a cigarette, coin, or pill between your thumb and index finger. That’s why it’s called a “pill-rolling” tremor.

What Causes Tremor?

Scientists have not yet solved the mystery of what causes the tremor but they have some good clues.

  • One of the fundamental causes of Parkinson’s disease is a loss of dopamine in the areas of the brain that support movements.
  • These movement-related brain sites are organized into circuits that specialize in producing various types of movements.
  • One of these circuits involves a regulatory brain region known as a thalamus.
  • The thalamus helps to regulate movements by relaying sensory information about movements from the senses up to the brain. The brain uses this "sensory feedback" from the thalamus to control complex movements.
  • Loss of dopamine in the brain circuit containing the thalamus disrupts operations of the thalamus.
  • Many studies have shown that the fall in overall dopamine levels in the thalamic circuit begins years before the onset of tremor and PD.
  • When the levels of dopamine reach a critically low level, the thalamus loses its normal regulatory input and tremor ensues.

When the brain cannot get accurate sensory feedback about how well movements are proceeding, it can no longer effectively correct bad movements or adjust slow movements and so forth. The most complex movements, such as movements of the fingers and hands, are the first to be affected, and the most affected.

The best treatment option for resting tremor is still dopamine replacement therapy.

View Article Sources
  • National Institute of Neurological Disorders and Stroke. "Parkinson's Disease: Hope Through Research."
  • R. Pahwa and K.E. Lyons (Editors), Handbook of Parkinson’s Disease; 4th Edition, New York, Informa Healthcare Publishers, 2007.