Pediatrics

Essential tremor

OVERVIEW: What every practitioner needs to know

Are you sure your patient has essential tremor? What are the typical findings for this disease?

Tremor is a rhythmic and symmetrical oscillation of one or more body parts about a fixed point, axis, or plane.

Tremors can be classified by the evoking event:

Rest tremor occurs in the absence of action and can be enhanced with stress.

Action tremor occurs when a voluntary action is performed. Subtypes include:

Postural (stationary, but against gravity)

Isometric (stationary but exertion against a stationary object)

Kinetic (while moving)

Intention/terminal (while moving the limb toward a target)

Essential tremor is a hereditary tremor common in adults, but described in children as well. Diagnostic criteria include:

Tremor (usually action tremor) with a frequency of 4-11 Hz but can be 5-9 Hz in children

Tremor typically involves the hands or head and is bilateral

No other neurologic signs or symptoms

Most parents will note the tremor when the child is holding a cup or glass or will comment on poor handwriting skills.

Severity parallels the emotional state (worse when nervous, upset, stressed).

A family history of tremor is helpful but not required. Note that the presence of tremor in a family member does not exclude the presence of another disease in the child.

In adults with essential tremor, the tremor is quieted with alcohol ingestion. Of course, this response is unlikely to be noted in children.

What other disease/condition shares some of these symptoms?

There is a broad range of causes of tremor. Common ones include:

Genetic

Essential tremor

Metabolic

Hypoglycemia

Hypocalcemia

Hypomagnesemia

Galactosemia

Biopterin synthesis defect

Phenylketonuria

Hepatic encephalopathy

Neurodegenerative

Wilson disease

Mitochondrial encephalopathy

Juvenile Huntington disease

Juvenile Parkinson disease

Medications

Anticonvulsants

Tricyclic antidepressants

Lithium

Selective serotonin reuptake inhibitors

β-adrenergic agonists

Levothyroxine

Toxins

Lead

Mercury

Toluene

Nutritional

Folate

Endocrine

Hyperthyroidism

Hyperadrenal state

Structural

Thalamic lesion

Inflammatory

Cerebellitis

Peripheral neuropathy

Benign

Enhanced physiologic

Psychogenic

What caused this disease to develop at this time?

A bimodal distribution in childhood has been reported, with onset in either the first or second decade of life.

Onset is rarely acute and can be quite subtle in younger children. Teenagers are more aware of the tremor and often note it to be exacerbated by emotional state.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

For a child with a history consistent with essential tremor and normal neurologic examination, no laboratory studies are indicated.

If there is concern for tremor secondary to a medical condition, complete blood count, complete metabolic panel, ceruloplasmin level, rheumatologic studies, thyroid studies, heavy metal screening, lead level, and toxin screen should be obtained.

Would imaging studies be helpful? If so, which ones?

For the child with tremor in isolation, as in essential tremor, and a normal neurologic examination, imaging studies are typically not warranted.

If the tremor is associated with other neurologic signs or symptoms, magnetic resonance imaging is the preferred imaging modality.

If you are able to confirm that the patient has essential tremor, what treatment should be initiated?

If the tremor is not interfering significantly with activities of daily living, such as writing, feeding, or social embarassment, medication is not indicated.

Adaptive devices, such as weighting of wrists, can help children whose tremor is affecting handwriting.

For children who wish to minimize the impact of tremor, the first-line therapy used in adults is beta-blockers such as propranolol. Standard dosing is 30 mg daily, titrating to effective tremor control or side effects.

Should beta-blockers fail, alternative medications include benzodiazepines (clonazepam), gabapentin, pregabalin, or topiramate

Primidone 25 mg at bedtime is effective as well.

Second-line therapies such as botulinum toxin injections, ablative brain surgery, or deep brain stimulation have not been well studied in children but are effective in adult patients.

What are the adverse effects associated with each treatment option?

Propranolol can cause sedation and orthostasis and should not be considered in patients with asthma, certain cardiac disorders, and those with insulin-dependent diabetes.

Clonazepam can cause sedation.

What are the possible outcomes of essential tremor?

The tremor is rarely progressive in childhood, but can slowly worsen over time in adulthood.

Presumption is that duration of tremor correlates with severity and dysfunction, but this has not been well studied.

What causes this disease and how frequent is it?

The prevalence of essential tremor is estimated at 0.3%-5.6% of the general population in adults

The true prevalence in children is not well known, although up to 50% of individuals with essential tremor reported onset of tremor in childhood.

Essential tremor is inherited in an autosomal dominant fashion.

A marker on intron 3 of the LINGO1 gene on chromosome 15q24.3 is significantly associated with essential tremor.

Other loci of interest include:

EMT1 (chromosome 3q13)

EMT2 (chromosome 2p22-25)

Chromosome 6p23

What is the evidence?

Ferrara, J, Jankovic, J. "Epidemiology and management of essential tremor in children". Paediatr Drugs. vol. 11. 2009. pp. 293-307.

Louis, ED. "Essential tremor". Handb Clin Neurol. vol. 100. 2011. pp. 443-48.

Sullican, KL, Hauser, RA, Zesiewicz, TA. "Essential tremor. Epidemiology, diagnosis and treatment". Neurologist. vol. 10. 2004. pp. 250-8.

Deuschl, G, Raethjen, J, Hellriegel, H. "Treatment of patients with essential tremor". Lancet Neurol. vol. 10. 2011. pp. 148-61.

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