Essential Tremor in Childhood
Recent research indicates that 5 out of every 100 children under the age of 20 has Essential Tremor. That number is staggering, and represents a significant increase in the incidence of ET in children from even ten years ago.
There is often a family history of tremor. In my study of hereditary essential tremor 25% of people with ET developed tremor in their first decade and 60% in their second decade. No tremor related disability was present before the age of ten. However, 55% of young people with ET had disability and 25% reported social handicap by the age of 20 years old.
ET inevitably affects the hands in childhood but head tremor is relatively rare, being apparent in about 5% of children. The types of hand tremor present are:
1. 20% have kinetic tremor only (i.e. tremor present only when the hands are moving).
2. 5% have postural tremor only (i.e. tremor is visible when the hands are held outstretched).
3. 75% have both postural and kinetic tremor.
The functional impact of ET in children includes difficulty with:
1. Holding a hot drink
2. Drinking from a cup
3. Using a spoon
7. Using tweezers
8. Painting nails
9. Playing a musical instrument
The frequency (the number of tremor cycles per second, measured in Hz from the fingers) of ET in children is interesting, having a lower frequency in the 7-12 years than the 14-16 years age range (average 5.3Hz compared to 9.0Hz respectively). Curiously putting a 300 gram weight on the fingers of young (7-12 years old) children increases the tremor frequency from 5.3Hz to 8.2Hz, whilst in teenagers and adults it has no effect on tremor frequency. When electromyographic (EMG) recordings of tremor are made from children with ET, the tremor has an alternating pattern between the flexor and extensor muscles of the forearm (i.e. the tremor is caused by bursts activity in the muscles of the finger flexors, then finger extensors, then flexors then extensors and so on).
Tremor in children may be associated with dystonia (sustained muscle spasms) or tics. In addition an over-active thyroid gland may cause tremor and so a blood sample for thyroid function tests may be required.
Very little is known about the treatment of ET in childhood, although small doses of propranolol (20-60mg) have been reported to help small numbers of children. There are no proper randomized placebo controlled studies of any treatment for ET in children.
The psychology of children is a very complex field. However, one way of preparing a child with ET for the almost inevitable school playground comments, is where possible, to be open about the condition.
Conclusion Essential tremor affects about 5% of children. It predominantly involves the hands and may produce disability and handicap by the second decade. When necessary small doses of propranolol may be helpful, although there are no controlled trials to prove that it is effective for ET in children (unlike adults where there is class A evidence to support its use). A common sense open approach about the condition is probably wise.Dr Peter G Bain MA MD FRCP Reader & Consultant in Clinical Neurology Division of Neurosciences, Charing Cross Hospital, Imperial College London