The value of F-EMG came home to me when my wife, who was complaining of bilateral foot pain, had a standard EMG. The first two pain specialists she saw recommended an EMG, but I explained why this was fruitless. When a third pain specialist mentioned that he refers patients to the “best local neurologist” I encouraged my wife to make an appointment. I was certain that standard EMG will be negative, since she had a single nerve root (Left S1). Muscles receive overlapping innervation from adjacent nerve roots, so two or more adjacent nerve roots must have gross damage before standard EMG can even begin to detect radiculopathy.
Note: Motor unit over lapping (adjacent nerve roots innervating the same muscle) is not a factor in F-EMG. A single motor unit’s dysfunction disrupts muscle metabolism, which is reflected in functional change. This is why oscilloscope waveform interpretation is meaningless in F-EMG and of questionable value in standard EMG.
The picture at right shows my wife’s atrophied left calf (white lines are of equal length). The atrophy was the result of left S1 entrapment caused by post operative pelvic adhesions. Her F-NCS was negative so there is no pain fiber involvement. Her F-EMG found 80% stronger voltage was required to cause the left S1 motor unit to activate muscle contractions as compared to the right.
Though the neurologist noted the atrophy in his report he did not explain EMG cannot diagnose a single root lesion. However, he did explain to my wife; “Symptoms such as yours are likely due to hysteria that females common have.” As we drove home I explained about standard EMG not being able to detect single root lesions. What most upset her was him blaming her symptoms on hysteria. I explained that she, like non-neurologists, are unaware that psychiatry as a branch of neurology, which means that neurologists either have psychiatric degrees or are at least highly trained in a subjects that studies psychosomatic disorders and placebos effects. In my opinion this makes many neurologists focus on giving patients hope rather than simply telling the truth that EMG is very ineffective. On top of this, there are monetary considerations. After all they make a comfortable living performing EDx studies. Also, to admit EMG’s limitations would drastically undermine referrals from ill-informed non-neurologist and expose the fact that they have been dishonest for several decades.
