Cramp-fasciculation syndrome (CFS) is a rare condition of the muscles characterized by persistent muscle cramping and twitching (fasciculations) in otherwise healthy individuals. This can lead to muscle discomfort, pain, or tiredness. Muscles in the leg are most commonly affected, although this condition may involve several parts of the body. Symptoms are thought to be due to over-activity of the associated nerves. In most cases, CFS occurs sporadically in people with no family history of the condition. There is limited information about the treatment of CFS, but certain medications have been reported as beneficial in individual cases.

Cramp-fasciculation syndrome (CFS) may have multiple underlying causes. In general, it is thought to be related to abnormal excitability (overactivity) of peripheral neurons. However, in many people with CFS, the cause cannot be found (idiopathic CFS).

The following have been reported to be associated with CFS:

• Genetic or autoimmune dysfunction of ion channels
• Peripheral neuropathy
• Anterior-horn-cell disease
• Metabolic abnormalities
• Tumors (most commonly thymoma)

Some familial cases of CFS have been reported. To our knowledge, no genes have been found responsible for familial cases of isolated CFS (occurring without an associated disorder). Recently, a variant in a gene called TRPA1 was suggested to be responsible for autosomal dominant, carbamazepine-responsive CFS in a father and son. However, they were thought to have CFS as part of a more generalized hypersensitivity-hyperexcitability disorder that was causing various additional symptoms. More research involving a larger number of people with CFS is needed to identify possible genetic causes of familial and/or isolated CFS.

Cramp-fasciculation syndrome (CFS) is primarily associated with spontaneous, painful muscle cramps and muscle twitches (fasciculations), in the absence of an associated underlying diagnosis. Muscles in the legs (thighs and calves) are most commonly affected, although other muscles (such as muscles in the arm or chest) can also be involved. Other signs and symptoms may include burning or prickling sensations (paresthesias), muscle stiffness, over-responsive reflexes (hyperreflexia), anxiety, and fatigue. Symptoms are often triggered by physical activity and may be relieved by stretching exercises and/or massage. The severity of the condition varies significantly from person to person. In severe cases, CFS can interfere with daily activities and quality of life.

There is limited information in the medical literature about the treatment of cramp-fasciculation syndrome (CFS). Much of what is available describes individual cases. Some people with CFS improve without treatment. Treatment with carbamazepine, gabapentin, lamotrigine, or pregabalin (medications that reduce the hyper-excitability of nerves) was described as helpful in improving symptoms in individual cases. Immunosuppressive therapy (e.g., prednisone) has been used to treat cases of CFS that did not respond to other treatments. 

Decisions regarding treatment should be carefully considered and discussed with a knowledgeable healthcare provider.

A diagnosis of cramp-fasciculation syndrome is generally based on the presence of characteristic symptoms, in otherwise healthy individuals. A history of frequent muscle cramps, twitching, and pain (often worsened by exercise) without muscle weakness or wasting is suggestive of the condition. Some of these symptoms may be more obvious when a person is at rest (i.e. muscle twitching). It is important to rule out other conditions that may cause similar features.

Electromyography (EMG) or repetitive nerve stimulation studies may also be done to assess the health of muscles and the nerves that control them. In repetitive nerve stimulation studies, muscle responses are recorded when the nerves are repetitively stimulated by small pulses of electricity.