Tremors

I. Background
Tremors, which represent the most common type of movement disorder, are abnormal, involuntary, rhythmical movements (1,2). They all stop during sleep.
II. Pathophysiology
Tremors are of three basic types: rest, postural, and kinetic.
A. Rest tremors
These occur when the limb muscles are not activated and diminish with activity. They occur slowly in disease states such as Parkinson's disease, multiple systems atrophy, and supranuclear palsy, whereas they occur rapidly or suddenly in toxin or drug-induced and psychogenic states, including those brought on by phenothiazines, metoclopramide, and anxiety. Rest tremors have a relatively slow oscillation frequency.
B. Postural tremors
They are also referred to as essential, physiologic, benign, and familial tremors. They are usually gradual in onset. Benign causes include the essential/physiologic tremor, and acute causes include toxic drug and alcohol withdrawal, stimulant use, and metabolic states such as hyperthyroidism and stress Postural tremors are maximal with the limb maintained against gravity, are reduced by rest, and are not enhanced during voluntary movement.
C. Kinetic tremors
Simple kinetic tremor has variable frequency and does not change with purposeful movement. Intention tremor has a low frequency that increases with directed movement. Etiology includes cerebellar lesions from causes such as stroke, tumor, multiple sclerosis, and drugs such as lithium and alcohol. Isometric tremor has a medium frequency and occurs with muscle contraction against a stationary object. Task-specific tremors occur only with specific tasks such as writing and sewing.
III. Evaluation
The history and physical examination remains the most valuable tool for the evaluation of a tremor.
A. History
A detailed history should include:
  • Duration, progression, and aggravating and ameliorating factors. Relationship to stressful events is particularly useful in evaluating for psychogenic causes
  • Family history of neurologic and metabolic disorders
  • Medication history to include alcohol, tobacco, and illicit drug use. Over-the-counter drug use such as decongestants, weight loss preparations, and herbal products should be elicited, because many people believe them to be free of side effects.
B. Physical examination
This should begin with observation with the patient at rest during the interview. The examination should document the following:
  • Relative frequency (fast or slow) and amplitude (fine or coarse) of the tremor as well as symmetry and the effect of position, rest, and actions
  • Affected body parts (e.g., head, hands, arms, legs, feet)
  • Any related findings such as tachycardia, hypertension, exophthalmia, thyromegaly, abnormal skin pigmentation, muscle rigidity, cog wheeling, and hyper-reflexiveness or hyporeflexiveness.
C. Testing
Testing should be directed by the history and physical examination. Generally, a comprehensive metabolic panel with tests of liver, kidney, thyroid functions, blood glucose, and complete blood count are appropriate for most tremors.
  • Computed tomography or magnetic resonance imaging may be indicated in cerebellar tremors.
  • Cerebrospinal fluid analysis, including immuniglobulin G (IgG) analysis, may be necessary if multiple sclerosis is suspected.
  • Appropriate drug and alcohol screens are indicated by the history and physical examination.
  • Positron emission tomography and single photon emission computed tomography are undergoing clinical usefulness trials.
IV. Diagnosis
The most critical step is to differentiate benign tremors from those with more ominous consequences. Treatment is based on the classification of the tremor. Therapeutic trials of drugs such as β-blockers may be useful in differentiating some types of tremor.
References
1. McGraw-Hill's Access Medicine, Harrison's Online. Part 2. Cardinal manifestations and Presentation of Diseases. Section 3. Nervous System Dysfunction. Chapter 21. Weakness, Disorders of Movement and Imbalance. Movement Disorders.
2. Sharon Smaga MD. Tremor. Am Fam Physician 2003;68(8):1545 - 1552.