What is known about Electrophysiological Muscle Functions of Patients with Fibromyalgia Syndrome?

Fibromyalgia syndrome (FM) is a disorder characterized by widespread pain, in particular, muscular pain. It is known that central pain processing in FM is deregulated. This results in pain augmentation, a phenomenon termed central sensitization. In addition, there is growing evidence of muscle dysfunction in FM, especially in respect to electrophysiological muscle phenomena. This paper presents what is known from the literature about electrophysiological muscle functions in patients with FM. Two important phenomena have been shown in the last decade in patients with FM: a) an increased muscle fiber conduction velocity (CV) in their non-painful and non-tender point-related muscles and, b) a tendency to develop myofascial tender points (MTPs). MTPs are very painful spots that are irritable on physical examination (much pain, with referred sensations), and electrically hyper-reactive, as they reveal local vigorous activity with needle electromyography. Studies have shown that MTPs, as a source of pain, may play a crucial role in initiation and maintenance of central sensitization. The Conclusions are, 1) there is already much known about electrophysiological dysfunction in muscles of patients with FM. 2) The main feature is one of overall muscle hyperactivity/hyperexcitability. 3) A question arises as to whether both electrical phenomena, that is the increased CV and the tendency to produce MTPs in FM, have a common underlying factor. 4) If so, which factor is it? Is the factor intrinsic (i.e. the muscle itself), or extrinsic (i.e. related to a disturbance in the central motor regulation, a neurohormonal influence, or chronic low-level mental stress)?