Clinical Conditions Associated with Tremors

Familial and Essential Tremor

Familial and essential tremors are the most common conditions associated with action tremor. In the familial, or hereditary form, several members of the same family are affected. This is a genetically heterogeneous condition, and more than one gene might be involved.

The non-familial form is referred to as essential tremor because it is not associated with any other neurological condition. The term "benign essential tremor" has been used in reference to this tremor; however, this is misleading since the tremor can be very severe and disabling. The essential and the familial hereditary forms are similar in clinical presentation.

• In some affected individuals the tremors start in infancy, however, more often they appear in the second and third decade of life and are most prevalent when a person is in his/her 60's. The incidence of the disease is around 4% of the population after the age of 40 and 6% after the age of 65.
  
  
• It is seen in both sexes with similar frequency.
  
  
• Most often, the first signs of tremors are seen in the arms, usually in both of them.
  
  
• The condition is chronic and, in many instances, progressive; as time goes by, other regions are involved including the head, neck, chin, and mouth.
  
  
• The tremor in the arms interferes with many activities such as eating and drinking.
  
  
• Other clinical manifestations might be a tremulous voice, a continuous head movement in a vertical "yes, yes" or horizontal "no, no" pattern.
  
  
• The legs are rarely affected.
  
  
• The tremor might be severe enough to result in functional disability.
  
  
• Tremors increase with anxiety and stimulant drugs and may decrease with the ingestion of alcohol.

There is no diagnostic test that confirms the condition. The diagnosis is based on clinical findings. However some tests might be indicated to rule out other conditions.

Parkinsonian (rest) Tremor

This type of tremor is predominant in the Parkinsonian syndrome

The better known of these conditions is Parkinson's disease, a degenerative progressive disorder of the brain that predominantly affects a deep structure of the brain called the substantia nigra, located in the basal ganglia. The cause of the disease is unknown, the strongest associated risk factor being age. In some individuals, genetic factors might be important.

In Parkinson's disease the tremor is the most common initial sign. This is followed by:

• gait disturbances, characterized by a shuffling gait and stooped posture;
  
  
• stiffness in the muscles;
  
  
• a general slowness in motor activities;
  
  
• muscle pain; and
  
  
• lack of dexterity.

In addition, the patients present with loss of facial expression and slowed speech with repetition of words. The symptoms progress slowly, and as the disease progresses the tremors are more prominent.

Other conditions with Parkinsonian Tremors

Several conditions in which Parkinsonian tremor might be an important feature include:

Degenerative disorders

• Parkinson's disease (idiopathic form, cause unknown)
  
  
• Progressive supranuclear palsy
  
  
• Hungtington's disease
  
  
• Lewy body dementia
  
  
• Spinocerebellar degeneration

Infection-related

• AIDS
  
  
• Neurosyphilis

Vascular parkinsonism

• Small ischemic infarcts in the brain (lacunar state)

Drug/Toxin induced

• Neuroleptic agents
  
  
• reserpine (Harmonyl)
  
  
• Carbon monoxide intoxication
  
  
• Manganese intoxication

Other disorders

• Hydrocephalus
  
  
• Brain tumors
  
  
• Subdural hematomas
  
  
• Post-traumatic

Enhanced Physiologic Tremor

This is an action tremor similar to the essential tremor, best seen when the hands are outstretched and fingers spread apart. It is seen in association with intense anxiety and in situations of stress. It can also be associated with certain disease states such as hyperthyroidism and hypoglycemia; in withdrawal syndromes (alcohol or sedatives withdrawal for example); and associated with drugs [coffee, tea, lithium (Eskalith, Lithobid)].

Psychogenic Tremor

Psychogenic tremors are very complex and do not fit very well with any of the prior categorizations. Individuals with Psychogenic Tremor might show characteristics of action as well as resting tremors, with clinical features that change in short periods of time and with a degree of disability that is not proportional to the tremor. The onset of the tremor might be very acute and not related to any other diagnosed medical condition. In some cases, the tremor might be induced by suggestion. Some patients have a prior history of somatization (expressing psychological distress in terms of physical symptoms). In some cases, there is some secondary gain associated or attention-seeking behavior associated with the tremors.

This is a very challenging diagnosis. If an underlying emotional condition is diagnosed the patient should be referred to a psychologist or a psychiatrist.

Drug-induced Tremors

The use of many drugs and also toxins can result in tremors. Many of these drugs are indicated for treatment of medical conditions. In many instances, the tremor is an undesirable side effect that can be controlled simply by decreasing the medications. In other instances the medications have to be discontinued. In the case of tremors secondary to exposure to toxins, the individual should be removed from the source of the toxins. Additionally, some specific treatments are available.

The most common type of drug-induced tremor is the enhanced physiological tremor and is related to the use of drugs such as stimulants, steroids, antidepressants, and caffeine. The Parkinsonian tremor is also frequently seen as a drug-induced tremor in patients taking certain types of drugs.

The following is a list of drugs and toxins that can induce tremors in otherwise healthy individuals:

• valproic acid/divalproex sodium (Depakene/Depakote)
  
  
• Many antidepressants, particularly the tricyclics [for example, amitriptyline (Endep, Elavil) , imipramine (Tofranil)
  
  
• lithium (Eskalith, Lithobid)
  
  
• Neuroleptics: phenothiazines; butyrophenones
  
  
• Cocaine
  
  
• Beta-agonists
  
  
• dopamine
  
  
• theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin)
  
  
• Amphetamines
  
  
• methylphenidate (Ritalin, Ritalin SR, Ritalin LA)
  
  
• Thyroid hormones
  
  
• Quite frequently seen in withdrawal reactions
  
  
• Caffeine
  
  
• Nicotine
  
  
• Lead intoxication
  
  
• Alcohol intoxication
  
  
• Arsenic intoxication