title: Myofascial trigger points show spontaneous needle EMG activity.
abstract: Monopolar needle electromyogram (EMG) was recorded simultaneously from trapezius myofascial trigger points (TrPs) and adjacent nontender fibers (non-TrPs) of the same muscle in normal subjects and in two patient groups, tension headache and fibromyalgia. 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.
authors.affiliation: Department of Neurosciences, University of California, San Diego.
authors.forename: D R
authors.initials: DR
authors.lastname: Hubbard
authors.forename: G M
authors.initials: GM
authors.lastname: Berkoff
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D005260:Female; D005356:Fibromyalgia / Q000503:physiopathology*; D006261:Headache / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009470:Muscle Spindles / Q000503:physiopathology; D009132:Muscles / Q000294:innervation / Q000503:physiopathology*; D009209:Myofascial Pain Syndromes / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology