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Spasms, fasciculation (worm-like or “crawling” muscles), cramping, myoclonus (brief jerking movements, especially at night), tremors and other neurological symptoms are actually fairly common in CFS/ME/FM.
Muscular phenomena (spasms, fasciculation, and cramping) are usually due to reflexive muscle problems. That is, CFS/ME and FM cause muscle to tighten up, but high levels of tension can be expressed as crawling feelings, spasms, and frank cramping. These problems usually respond to heat or warming, massage, or supplementation with potassium, magnesium, and calcium. It is sometimes necessary to use prescription muscle relaxers (diazepam/Valium, metaxalone/Skelaxin, cyclobenzaprine/Flexeril, carisoprodol/Soma, and others) or quinine (available over-the-counter as Quinamm or Leg Cramp).
Tremors and myoclonus are thought to be due to a hyperexcitable nervous system. Some consider myoclonus a minor form of seizure. Hyperexcitability is best managed with relaxation/meditation techniques, biofeedback, magnesium (such as magnesium oxide or magnesium malate), GABA, B6, taurine, benzodiazepines (especially diazepam/Valium or clonazepam/Klonopin), and anti-epileptic drugs such as gabapentin/Neurontin , pregabalin/Lyrica, and others.”