Brief ReportElectrophysiological Changes After Human Muscle Tear A Potential ConfounderHearn, Sandra L. MD; Berri, Hassen M. DO; Little, Ann A. MD; Teener, James W. MD; Richardson, James K. MDAuthor Information From the Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan (SLH, HMB, JKR); and Department of Neurology, University of Michigan, Ann Arbor, Michigan (AAL, JWT). All correspondence should be addressed to: Sandra L. Hearn, MD, Burlington Office Center, 325 E. Eisenhower Parkway, Suite 100, Ann Arbor, MI 48108. Part of this research has been presented as a poster at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Assembly on September 15, 2016, New Orleans, LA. This study involved use of a medical device: a diagnostic electromyograph (Carefusion Nicolet EDX with Viking 4 Software, FDA 510(K) #K112052), used on-label to conduct electromyography and nerve conduction studies on subjects. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. American Journal of Physical Medicine & Rehabilitation: July 2020 - Volume 99 - Issue 7 - p 645-648 doi: 10.1097/PHM.0000000000001346 Buy Metrics Abstract The goal of this prospective electrophysiologic study is to describe the chronological electromyographic findings observed in a human gastrocnemius muscle after a traumatic tear. A 30-yr-old man sustained a tear of the medial gastrocnemius. Needle electromyography was performed serially at 5, 15, and 26 wks after injury, with the contralateral gastrocnemius muscle serving as a control. Audiovisual recordings of the studies were analyzed in a blinded manner. Five weeks after injury, the affected gastrocnemius displayed increased insertional activity on electromyography. By 15-wk postinjury, insertional activity had diminished. However, motor unit action potentials showed chronic neurogenic morphological changes not previously observed. These changes persisted 26 wks after injury. The study findings reveal a chronological trajectory of increased insertional activity followed by reinnervation changes in a human muscle after local trauma, paralleling a course previously observed in a rat model. Electrodiagnosticians unaware of this phenomenon are at risk for making erroneous interpretations when examining patients with a history of muscle trauma. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.