Shaking Hands (Hand Tremors)

Hand tremors are abnormal, repetitive shaking movements of the hands. Hand tremors have many causes and can be inherited, related to illnesses (such as thyroid disease), or caused by fever, hypothermia, drugs, or fear.

There are two main categories of hand tremors:

• normal (also called physiologic)
• abnormal (or pathologic)

Normal or physiological tremors are fine, almost imperceptible, tremors that are difficult to see with the naked eye and do not interfere with activities. It can be seen in the fingers when the arms are outstretched. The frequency of the contractions is in the area of 8 to 13 cycles per minute. The cause of this type of tremor is not known, but it is not considered to be associated with any disease process.

Abnormal or pathological tremors are more obvious and visible to the naked eye. As such, this type of tremor does interfere with everyday activities. The frequency of the contractions is in the area of 4 to 7 cycles per minute. In many instances, the tremor is associated with defined medical conditions.

Most often the abnormal tremor is observed in the distal parts of the limbs (hands, fingers); however, every part of the body (such as the head, the tongue, the vocal cords, or the trunk) can be affected by the tremor.

The clinical distribution of the tremor might be different depending upon the medical condition associated with it and some individual factors. However, in a particular individual, the quality and distribution of the tremor are very constant.

Abnormal tremors can be subclassified into the following categories:

• Resting tremor (also call Parkinsonian tremor) is observed in a body part that is not active and is completely supported against gravity. It is a coarse, rhythmic tremor, often localized in the hands and forearms, but less frequently seen in other parts of the body, and is observed when the limb is in a position of rest. Intentional movements may decrease the intensity of the tremor. However, the tremor disappears when the limbs are at extreme rest, as is the case when the patient is sleeping. This phenomenon is common to most tremors. In the hands, the tremors result in a peculiar "pill-rolling" movement of the fingers, more obvious between the thumb and the index finger. Other parts of the body might also be affected. For example, the eyelids tend to flutter, and the jaw and the lips can flicker. When the legs are impaired it might result in gait (walking) problems. This tremor is most often seen as a manifestation of Parkinson's syndrome.
• Postural, or action tremor, is observed when muscles voluntarily contract. This tremor is exhibited with any attempt to keep the limbs or trunk in a particular position, for example, to keep the arms outstretched. This type of tremor becomes worse when the limb is actively moved, for instance, when trying to drink from a cup. However, no tremor is observed when the limb is fully relaxed. This tremor is most often seen as a manifestation of an essential tremor.
• Intention (ataxic) tremor can be a very disabling type of tremor. It has some of the characteristics of the action tremor in the sense that it is triggered by movement; however, its main feature is that it occurs at the end of an action when a fine, precise adjustment is needed. For example, when a person is asked to touch the tip of the nose, the early part of the action does not elicit the tremor, but as soon as the finger is near the nose and has to zero in on the tip of the nose, an irregular, rhythmic tremor with a frequency of 2 to 4 oscillations per minute is seen. Unlike action and resting tremors, the oscillations are in different planes and may persist even after the task is achieved. This type of tremor is mostly seen in conditions associated with the cerebellum or its neurological connections.
• Rubral tremor is characterized by intense, violent movement. With this type of tremor, a patient's slight movement of the arms or attempts to maintain a static posture, like trying to keep the arms outstretched, results in an intense rhythmic "wing-beating" movement. It is also associated with some interruptions of cerebellar connections. This type of tremor is seen most often, among other conditions, in persons with multiple sclerosis.

In general, one particular tremor type is predominant and sometimes the only tremor present in a defined clinical condition, for example, resting tremor in Parkinson's disease or postural tremor in essential tremor. However, there are several individual variations, and it is not unusual for a patient with a defined clinical condition, for example, Parkinson's disease, to have, besides the resting tremor typical of the disease, some degree of postural tremor.

Symptoms related to hand tremors include:

• Seizures
• Muscle cramps
• Weakness

The causes of tremors are very diverse. However, even though the list of potential causes is very extensive, a few conditions are predominant. The most important will be discussed here. The following are clinical conditions that may cause hand tremors and other types of tremors.

Familial and Essential Tremors

Familial and essential tremors are the most common conditions associated with action tremors. 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 60s. 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) Tremors

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.

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

Degenerative Disorders

• Parkinson's disease (idiopathic form, cause unknown)
• Progressive supranuclear palsy
• Huntington'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