From the Guidelines
The term for a brief, spontaneous contraction affecting a small number of muscle fibers, often causing a flicker of movement under the skin, is called fasciculation. This condition is characterized by the spontaneous discharge of entire motor units, originating from either the motor neuron or distally along the axon, in an irregular pattern, as described in the study by Blitzer et al. 1.
Key Characteristics of Fasciculations
- Spontaneous discharges of entire motor units
- Irregular pattern, sounding like raindrops on a tin roof
- Often associated with neuropathy or motor neuron diseases, such as amyotrophic lateral sclerosis
- Can be benign and commonly occur in healthy individuals, especially after exercise, during periods of stress, or with caffeine consumption
Clinical Considerations
- Fasciculations can appear anywhere in the body but are most noticeable in larger muscle groups like the calves, thighs, or arms
- While usually harmless, persistent fasciculations may sometimes indicate underlying conditions, such as electrolyte imbalances, certain medications, nerve irritation, or rarely, neurological disorders
- Most occasional fasciculations require no treatment and resolve on their own, though addressing factors like adequate hydration, reducing caffeine intake, and managing stress may help decrease their frequency
- If fasciculations become persistent, widespread, or are accompanied by muscle weakness or other concerning symptoms, medical evaluation would be appropriate, as noted in the study 1.
From the Research
Definition of Fasciculation
- Fasciculation is a brief, spontaneous contraction affecting a small number of muscle fibers, often causing a flicker of movement under the skin 2.
- It is characterized by visible, fine, and fast contractions of muscle fibers, sometimes appearing as a wormlike movement under the skin 3, 4.
Causes and Associations
- Fasciculations can occur in various conditions, including amyotrophic lateral sclerosis (ALS), benign fasciculation syndrome, and other neurological disorders 5, 2, 6.
- They can also be associated with the use of corticosteroids, particularly after tapering off high doses 4.
- Fasciculations are distinct from other muscle contractions, such as those seen in neuromyotonia, and can be an early sign of motor neuron disease 2.
Diagnosis and Differentiation
- The diagnosis of fasciculations can be made through clinical examination, electromyography (EMG), and muscle ultrasonography (MUS) 3, 6.
- The intensity and distribution of fasciculations can help differentiate between ALS and non-ALS patients, with ALS patients typically showing higher grades of fasciculation and a more proximal distribution 6.
- Benign fasciculation syndrome can be diagnosed when fasciculations are present without other signs of neurogenic disorder or laboratory findings 4.