Benign Fasciculation Syndrome - Diagnosis

Diagnosis

Diagnosis of BFS is a "diagnosis of exclusion," in other words, other likely causes for the twitching (mostly forms of neuropathy, such as borreliosis (Lyme disease) neuropathy, motor neuron diseases such as ALS, etc.) must be eliminated before BFS can be assumed. An important diagnostic tool here is the electromyography (EMG). Since BFS appears to cause no actual nerve damage (at least as seen on the EMG), patients will likely exhibit a completely normal EMG (or one where the only abnormality seen is fasciculations).

Another important step in diagnosing BFS is checking the patient for clinical weakness. Clinical weakness is often determined through a series of strength tests, such as observing the patients ability to walk on his or her heels and toes. Resistance strength tests may include raising each leg, pushing forward and backward with the foot and/or toes, squeezing with fingers, spreading fingers apart, and pushing with or extending arms and/or hands... In each such test the test provider will apply resisting force and monitor for significant differences in strength abilities of opposing limbs or digits. If such differences are noted or the patient is unable to apply any resisting force, clinical weakness may be noted.

Lack of clinical weakness along with normal EMG results (or those with only fasciculations) largely eliminates more serious disorders from potential diagnosis.

Another abnormality commonly found upon clinical examination is a brisk reflex action known as hyperreflexia. Standard laboratory tests are unremarkable. According to neurologist John C. Kincaid:

In the absence of clinical and electromyographic findings of neurogenic disease, the diagnosis of benign fasciculations is made. I suggest that patients like this be followed for a year or longer with clinical and electromyographic exams at about 6-month intervals before one becomes secure in the diagnosis that the fasciculations are truly benign. My approach to treating fasciculations that appear to be benign is to first reassure the patient that no ominous disease seems to be present.