Benign fasciculation syndrome (BFS) is a neurological disorder characterized by fasciculation (twitching) of various voluntary muscles in the body. The twitching can occur in any voluntary muscle group but is most common in the eyelids, arms, legs, and feet. Even the tongue may be affected. The twitching may be occasional or may go on nearly continuously. Any intentional movement of the involved muscle causes the fasciculations to cease immediately, but they may return once the muscle is at rest again.
Another common feature of the disorder, when seen by physicians, is an increase in the patient's level of anxiety, especially health-related anxiety. It's not uncommon for the patient to fixate on ALS, MS, ME, Parkinson's, vCJD,Wilson's Disease, or some other serious neurological disorder, refusing to believe the BFS diagnosis. Since it is anxiety, not fasciculations, that brings patients to physicians, the association of BFS and anxiety is probably an example of ascertainment bias.
The precise cause of BFS is unknown, and, in fact, it's not known if it's a disease of the motor nerves, the muscles, or the neuromuscular junction. Mitsikostas et al found that fasciculations "were slightly correlated to the body weight and height and to the anxiety level" in normal subjects. Another factor that seems to be common in many cases is a history of regular strenuous exercise. Attention deficit disorder (or drugs used to treat it) and/or a related disorder may be a contributing factor, and people with essential tremor appear to have a greater than normal likelihood of developing BFS. In addition, there are likely other genetic and environmental factors that make the patient more susceptible to BFS.
There are some intriguing similarities between BFS and chronic organophosphate poisoning, but these similarities have not been explored. It may be that chronically elevated levels of stress hormones in the body cause symptoms similar to those caused by organophosphates.
In many cases, the severity of BFS symptoms can be significantly reduced through a proactive approach to decrease the overall daily stress. Common ways to reduce stress include: exercising more, sleeping more, working less, meditation, and eliminating all forms of dietary caffeine (e.g. coffee, chocolate, cola, and certain over-the counter medications).