myotonic discharge
1,278
Published 2018-11-06
Recording kindly donated by Dr. Vasiliki Tsirka. The data are shown twice (two different time scales). Individual muscle fibres firing runs of action potentials. The potentials wax and wane in frequency and in amplitude.
The AANEM defines a myotonic discharge as follows: Repetitive discharge which occurs
at rates of 20 to 80 Hz. There are two types: 1) biphasic (positive-negative) spike potentials less than 5 ms in duration resembling fibrillation potentials. 2) positive waves of 5 to 20 ms duration resembling positive sharp waves. Both potential forms are recorded after needle electrode insertion, during or following voluntary muscle contraction or after muscle percussion, and are due to independent, repetitive discharges of single muscle fibers. The amplitude and frequency of the potentials must both wax and wane. This change produces a characteristic musical sound in the audio output of the electromyograph due to the corresponding change in pitch, which has been likened to the sound of a “dive bomber.”
www.aanem.org/getmedia/c5e5be57-49ea-4600-b4c7-dde…