Benign fasciculation syndrome

Benign fasciculation syndrome (BFS) is characterized by fasciculation (twitching) of voluntary muscles in the body.

The main symptom of benign fasciculation syndrome is focal or widespread involuntary muscle activity (fasciculation).

The benign twitches usually have a constant location.

The tongue can be affected.

The twitching can occur in any voluntary muscle group but is most common in the eyelids, arms, hands, fingers, legs, and feet. 

Twitching may be occasional to continuous.

Other common symptoms are generalized fatigue or weakness, paraesthesia or numbness, and muscle cramping or spasms.

Anxiety and somatic symptom disorders are commonly reported.

Muscle stiffness may also be present.

Cramp fasciculation is a variant of BFS which presents with muscle pain and exercise intolerance.

BFS symptoms are typically not accompanied by severe muscle weakness.

BFS symptoms are typically present when the muscle is at rest. 

There may be a perception of weakness,and the sensation of a fatigued limb, but is not true clinical weakness. 

Fasciculations can move from one part of the body to another.

Its precise cause is unknown, and is not known if it is a disease of the motor nerves, the muscles, or the neuromuscular junction.

Anxiety disorders may be caused among individuals who become concerned they have a motor neuron disease.

Fasciculations can be caused or worsened by long and intense periods of daily exercise.

BFS can also be caused by long-term use of anticholinergics, exposure to steroids, nicotine, caffeine, alcohol, insecticides and pesticides.

Fasciculations can also be caused by deficiencies of magnesium and/or calcium, and thyroid disease.


A diagnosis of exclusion; that is, other potential causes for the twitching must be ruled out before BFS can be diagnosed. 

Diagnosis includes blood tests, a neurological exam, and electromyography (EMG).[2]

Lack of clinical weakness along with normal EMG results largely eliminates more serious disorders from potential diagnosis.

Diagnosis is made when there is no clinical finding of neurogenic disease.

Differential diagnosis:

Motor neuron diseases (MND) such as amyotrophic lateral sclerosis (ALS), neuropathy, and spinal cord diseases.

The  fasciculations of  motor neuron diseases are often abrupt and widespread at onset in an individual previously unaffected by fasciculations in youth. 

It is exceptionally rare for patients later diagnosed with ALS to present with fasciculations alone”, and ALS is ruled out with a normal EMG and no evidence of muscle wasting.


Treating any accompanying anxiety using cognitive behavioral therapy or antidepressants.

Quinine is effective, but not recommended because of the potential for serious side effects.

Calcium channel blockers may be effective, although the evidence for their use is weak.

In cases caused by magnesium or calcium deficiencies, curing the deficiency through diet or supplementation is effective.

Prognosis is excellent, with no known long-term physical damage. 

Some individuals remain anxious.

Spontaneous remission has been known to occur.

There may be an association between widespread fasciculations or paresthesias with small fiber neuropathy.

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