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Do ALS fasciculations come and go?

ALS (amyotrophic lateral sclerosis) fasciculations are involuntary muscle twitches caused by the degeneration of motor neurons in ALS. Whether ALS fasciculations come and go can vary from person to person.

What are ALS fasciculations?

ALS fasciculations are brief, spontaneous contractions of muscle fibers innervated by motor neurons affected by ALS. They appear as flickers or twitches under the skin and can occur in any muscle area, though commonly first appear in the arms, legs, shoulders or tongue.

Fasciculations occur because as motor neurons degenerate in ALS, they become overly excitable and discharge abnormal impulses to muscle fibers. This causes the muscle fibers to briefly contract, producing a visible twitch.

Do ALS fasciculations come and go?

For many people with ALS, fasciculations can be transitory and shift locations, giving the impression that they “come and go.” However, this is not always the case, and there are a few factors that influence whether ALS fasciculations are sporadic or persistent:

  • Stage of ALS progression – Early on, fasciculations may be infrequent and sporadic before becoming more widespread and constant as the disease advances.
  • Location – Some body areas are more prone to long-lasting fasciculations, such as the thighs, calves, triceps and tongue.
  • Exertion – Strenuous exercise can trigger temporary fasciculations.
  • Stress/anxiety – Stress and anxiety can increase fasciculations.
  • Medications – Drugs like steroids may exacerbate fasciculations.

While fasciculations tend to become more persistent as ALS progresses, they rarely disappear completely. Brief, painless muscle twitches are a hallmark symptom of ALS throughout disease course.

Patterns of ALS fasciculations

Although variable, ALS fasciculations often follow certain patterns:

  • They frequently start in one localized area such as the arm, leg or tongue before spreading.
  • Legs and proximal arm muscles tend to be initially involved before fasciculations appear elsewhere.
  • Chronic, unremitting fasciculations are characteristic of advanced ALS.

What triggers ALS fasciculations?

ALS fasciculations can be set off by various triggers:

  • Voluntary muscle contractions – Actions like flexing or stretching muscles can stimulate fasciculations.
  • Strenuous exercise – Vigorous exercise causes muscle fatigue, irritability and fasciculations.
  • Alcohol – Alcohol can enhance fasciculations.
  • Caffeine – High caffeine intake can increase excitability of motor neurons.
  • Stress and anxiety – Emotional stress increases neurotransmitter levels that facilitate fasciculations.
  • Cold temperatures – Muscle cooling enhances fasciculations by making motor neurons more excitable.

ALS fasciculations have also been noted to increase during relaxation, rest, sleep deprivation and fasting.

When do ALS fasciculations occur?

ALS fasciculations can occur at any time, though certain periods tend to provoke them:

  • During rest – Sedentary periods allow fasciculations to manifest.
  • When falling asleep – Relaxation when going to sleep triggers fasciculations.
  • Upon waking – Transitioning from sleep to wakefulness stimulates fasciculations.
  • When stressed – Anxiety and emotional tension exacerbate fasciculations.
  • During strenuous activity – Vigorous exercise leads to muscle fatigue that activates fasciculations.
  • With exhaustion – Physical and mental exhaustion enhance fasciculations.

Fasciculations may also increase in frequency during quiet observation of muscles and when focusing attention on them.

How long do ALS fasciculations last?

Individual ALS fasciculations are very brief, typically lasting less than a few seconds. However, at any given time multiple fasciculations may be occurring simultaneously in different muscles.

Overall, fasciculations tend to be a persistent symptom throughout the course of ALS. They may fluctuate in frequency and location, but rarely disappear entirely once they begin.


In summary, the appearance of ALS fasciculations can be variable from person to person. Early on they may seem to sporadically come and go before becoming more constant. While fasciculations can be triggered by certain factors and occur at variable times, they tend to persist as a symptom once present. Brief muscle twitches are a core feature of ALS that reflect the progressive degeneration of motor neurons controlling muscle fibers.