Electromyographic study on the striated urethral sphincter of the male. An analysis with turns amplitude diagram

Abstract

The aim of this study is to clarify the physiology and pathophysiology of two striated urethral sphincters, the periurethral striated sphincter (PUS) and the external urethral sphincter (EUS), in the voiding cycle, using a selective and semi-quantitative electromyographic technique. Under ultrasonic guidance, two needle-electrodes were inserted into the two sphincters of 31 males (7 neurologically normal, 13 with nuclear and/or infranuclear lesions, 11 with supranuclear lesions), and EMGs recorded during the whole cystometric course were analysed by the aid of Turns-Amplitude Diagram (TAD). The results obtained were as follows: 1) In neurologically normal cases, the increment of turns as well as amplitudes in EMGs of both the sphincters were observed with the bladder filling, and they were completely diminished at the onset of than voiding. 2) The increment of turns were more obvious than that of amplitudes in EMGs of both the sphincters. 3) More voluntary function could be assumed on EUS than PUS. 4) The functional sphincteric responsibility corresponding to the voiding cycle could be expressed by the direction and the length of the vectors obtained from TAD. 5) In neurogenic bladder cases, various abnormal sphincteric responsibility, such as the shortening and/or abnormal directions of the vectors, were found. With the results described above, this semi-quantitative assessment of sphincter EMG was thought to be useful to evaluate the abnormal activity of the urethral sphincter in neurogenic bladder cases.