Motor unit action potential (MUAP) parameters affected by editing duration cursors

Quantitative electromyography (QEMG) allows fast analysis of motor unit action potential (MUAP) parameters such as amplitude, duration, size index (SI), phases, turns and firing rate. When automated duration cursor placement is incorrect, the electrodiagnostician will manually edit this function potentially introducing bias to the final results.

To identify that (1) size index is the MUAP parameter least affected by manually editing duration cursors and (2) MUAP amplitude will influence the manual cursor correction rate.

Included were twenty-one consecutive patients who had QEMG with monopolar needle electrode for diagnostic evaluation of their myofascial pain symptoms. Evaluated for neck pain included 6 bilateral upper limb and cervical paraspinal muscles and for lower back pain were 5 bilateral lower limb and lower back muscles. Twenty MUAPs were recorded from each muscle and hardcopies of data obtained before and after manual edit.

Of a total of 5360 MUAPs analyzed 1764 (33%) required manual editing of duration cursors. Cursor correction rate 120 MUAP s/individual muscle analyzed was also similar at 33+/-17%. Percentage change in duration more so than turns, before and after correction, was significantly larger than that of other parameters. No significant differences in percentage changes noted between SI and phases.

SI and phases are least influenced by the manual correction of duration cursors since there is insubstantial amplitude and area at the tail-end of the MUAP.