Action tremor is a tremor that is most prominent when the limb is held out or being used (i.e., with action). Patients notice this tremor when holding a coffee cup, reading the newspaper, writing, or speaking in front of an audience. Action tremor worsens with anxiety or fatigue. Many people have a mild tremor that may be brought out with caffeine, stimulant medications, or theophylline derivatives. This is known as an exaggerated physiologic tremor. Other medications that may cause such a tremor include neuroleptics, tricyclic antidepressants, valproic acid, lithium, and steroids. Hyperthyroidism, pheochromocytoma, hypothermia, and drug and alcohol withdrawal also may cause an exaggerated physiologic tremor. Essential tremor is also an action tremor, but usually of greater amplitude than physiologic tremor. Essential
tremors may be seen as a genetically determined trait (familial action tremor). Essential and familial action tremors tend to gradually worsen over years, particularly when patients reach their 60s. One alcoholic drink will decrease action tremors temporarily. In fact, some patients self-medicate with alcohol to their detriment. Aside from the tremor, the neurologic examination is normal in action tremor patients.

Note: Consider Wilson disease in any young person with an unusual tremor.

Intention tremor is not a true tremor, but an impairment of the ability to guide limb movements accurately to their destination. An intention tremor is visible when the patient reaches for an object or the examiner’s finger. The patient’s arm begins to waver from side to side as it nears its goal, as the brain tries to correct for inaccurate movements. Intention tremor is a useful sign of ataxia. See Chapter 13 for further information on ataxic disorders.

Parkinsonism refers to a complex of alterations of movement that may be caused by Parkinson disease, or other disorders mimicking Parkinson disease. Features seen in parkinsonism include:

The resting tremor usually consists of a large amplitude, slow (3-7 Hz), “pill-rolling” tremor that is suppressed with movement, as opposed to action tremors that increase with movement. Often there is small handwriting (micrographia) and postural instability. The diagnosis of parkinsonism is made by history and clinical exam. There are no diagnostic imaging or laboratory tests.