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What is benign fasciculation?

Q What is benign fasciculation syndrome? Is it inherited or acquired? Does it resolve or is there treatment?

A Fasciculations are spontaneous, irregular, involuntary and painless rapid twitches in a muscle. They generate concern because of their known association with motor neurone disease(MND), although this is an uncommon presenting symptom.

Most people notice occasional fasciculations. Some will experience much more frequent fasciculations and the diagnosis of benign fasciculation syndrome (BFS) is appropriate when individuals have prominent, frequent fasciculations, occurring over months or years.

They may be provoked by stress, fatigue, exercise, alcohol or caffeine.

?-agonists, D-penicillamine and thyroxine therapy have also been implicated.

Sufferers may have minor cramping, paraesthesiae, myalgia or fatigue in addition to painless fasciculations. Neurological examination is normal, with no atrophy or reduction in muscle strength. Neurophysiological examination reveals fasciculations on needle electromyography, with no other abnormalities.

Studies of people with BFS, followed in some cases for over 30 years, show that none of them went on to develop MND or any other serious neurological disorder.

There is no treatment to reduce the fasciculations and reassurance that they are not sinister is usually the only therapy required.

The cause is unknown. The fasciculations represent spontaneous contractions of muscle fibres in a particular motor unit and are

thought to arise due to hyperexcitability in the distal axon rather than to abnormalities in the spinal cord or motor cortex.

One study reported an increased incidence of upper respiratory tract or gastrointestinal infection in the month before onset of fasciculations, suggesting BFS can develop after a mild, acute, generalised polyneuropathy.

Karen Morrison, Professor of Neurology, Head of the Department of Clinical Neurosciences, Honorary Consultant Neurologist,

Institute of Biomedical Research ,

The Medical School, University of Birmingham

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