Cramp-fasciculation syndrome

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.^[4][1] 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.^[1]

Cramp-fasciculation syndrome (CFS) may have multiple underlying causes.^[2] In general, it is thought to be related to abnormal excitability (overactivity) of peripheral neurons.^[2] However, in many people with CFS, the cause cannot be found (idiopathic CFS).^[2]

The following have been reported to be associated with CFS:^[2][3]

• 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.^[5] 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.^[5] More research involving a larger number of people with CFS is needed to identify possible genetic causes of familial and/or isolated CFS.

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.^[3]

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.^[3][6]

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.^[3] 

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

There is very limited information on the prevalence of cramp-fasciculation syndrome in the US and in the world. Because there are few published cases, many resources generally state that this condition is rare. To our knowledge there has only been one study investigating the prevalence of this condition. This Dutch study from 1991 found that 0.4% of men and 0.7% of women experience frequent fasciculations (muscle twitches) and muscle cramps.^[7]