Definitions

Tremor is a rhythmic, involuntary back-and-forth oscillation of part of the body. Tremor in children may be caused by familial essential tremor, focal epilepsy, or a psychogenic movement disorder. Tremor is often seen with ataxia, dystonia, or myoclonus. Physiologic tremor is the normal shaking that occurs when people attempt to exert large forces or lift heavy objects. If a child has weakness, this type of tremor may be accentuated. Ataxia may lead to tremor when the inaccurate movements are corrected and then repeatedly over corrected.

Tremor may occur...

• While at rest
• While maintaining a fixed arm position or posture (postural tremor)
• With movement or kinetic, action, or intention tremor

Tremor may occur in the hands, feet, back, neck, face, voice, or other parts of the body. The frequency of the tremor may be described by the number of cycles per second, or Hertz (Hz). Tremor may appear suddenly, or worsen gradually over months or years. Many types of tremor disappear during sleep, only to return the next day upon awakening. Tremor is often associated with other neurological disorders; therefore, it is important to look for the cause of tremor.

In familial essential tremor, the onset may occur at any age. Once started, this type of tremor often continues or become slowly worse with time. Some family members may notice that the tremor improves briefly after drinking alcohol. This type of tremor is usually postural, and may be particularly evident while the child attempts to eat or drink from an open cup.

Examination

The child is examined to determine which body parts are affected, as well as the frequency and amplitude of the tremor. The tremor is examined while the child is at rest, while holding a posture against gravity (e.g., as with the arms outstretched), and while reaching for targets. Tremor may be accentuated by attempting to drink from a nearly full cup of water. It may be difficult to distinguish myoclonic or dystonic tremor from "true" tremor. Frequently, the distinction depends upon whether or not other symptoms are present, such as dystonic posturing or stimulus sensitivity. The child's strength must be assessed, as enhanced physiologic tremor may become more apparent if there is muscle weakness. Family history of tremor is important, as several types of tremor, myoclonus, or dystonia may be inherited. It is also important to look for medications or toxins that are known to cause tremor.

Etiology

Benign:
Enhanced physiologic tremor, shaking/shuddering spells (although these may be a precursor to essential tremor), spasmus nutans.

Static (fixed) injury:
Stroke (particularly in the midbrain or cerebellum), multiple sclerosis

Degenerative:
juvenile parkinsonism, Wilson's disease, Huntington's disease, Tay-Sachs disease

Chemical/metabolic:
hyperthyroidism, hyper-adrenaline state (including anxiety or pheochromocytoma), hypomagnesemia, hypocalcemia, hypoglycemia, hepatic encephalopathy

Drug-induced:
valproate, lithium, thyroid hormone, tricyclic antidepressants, stimulants (cocaine, amphetamine, caffeine, thyroxine, bronchodilators), neuroleptics, cyclosporin, toluene, mercury, thallium, amiodarone, nicotine, lead, manganese, arsenic, cyanide, naphthalene, ethanol, lindane

Other causes of tremor:
peripheral neuropathy, cerebellar disease or malformation, psychogenic tremor, familial essential tremor

Workup

The workup of tremor depends upon the specific type of tremor and its possible cause. Any medications that may worsen tremor should be avoided, if possible. If the tremor had sudden onset, an MRI of the head may be able to show a stroke, multiple sclerosis, or other lesion.

Electroencephalogram (EEG), which measures electrical activity in the brain, is important if there is a suspicion that the tremor is due to focal seizures. If there has been gradual onset, it is important to check electrolytes, including glucose, calcium and magnesium, thyroid function, copper in the urine (for Wilson's disease), and possibly the amount of adrenaline metabolites (for pheochromocytoma). If parkinsonian features are present, a trial of L-DOPA may be helpful. Rarely, an EMG may help to determine if the tremor is more likely to be due to dystonia or myoclonus. Tests for myoclonus, including EEG with back-averaging and SEP, may help to confirm the presence of dystonia or myoclonus. If there is a family history of tremor, it may be helpful to try the use of alcohol. This is often tried with an adult family member, rather than the child. If the tremor improves with alcohol, this suggests that it will also improve with other medications, including the dopamine agonist primidone.

Often, mild tremor does not require treatment. If there is a specific illness such as Parkinson's or Wilson's disease, tremor will improve with appropriate therapy for the underlying condition. Otherwise, symptoms may often be treated with propranolol, primidone, or benzodiazepines (i.e., clonazepam, diazepam, lorazepam). In all cases, the child should start with a very small dose. The dose should be increased gradually in order to avoid side effects. If the tremor is felt to by psychogenic, then psychotherapy may be helpful in determining and avoiding any psychiatric triggers for the movement.