Myofascial Trigger Points Show Spontaneous Needle EMG ActivityHubbard, David R., MD*,†; Berkoff, Gregory M., DC†Spine: October 1993 - Volume 18 - Issue 13 - p 1803–1807 Diagnostics/Imaging: PDF Only Buy Abstract Author InformationAuthors Monopolar needle electromyogram (EMG) was recorded simultaneously from trapezius myofesial trigger points (TrPs) and adjacent nontender fibers (non-TrPs) of the same muscle in normal subjects and in two patient groups, tension headache and flbromyalgia, Sustained spontaneous EMG activity was found in the 1–2 mm nidus of all TrPs, and was absent in non-TrPs. Mean EMG amplitude in the patient groups was significantly greater than in normals. The authors hypothesize that TrPs are caused by sympathetically activated intrafusal contractions. *Department of Neurosciences, University of California, San Diego; and the †Pain Research Institute, Rehabilitation Center; Sharp Memorial Hospital, San Diego, California. © Lippincott-Raven Publishers.