URETHRAL SPHINCTER NEEDLE ELECTROMYOGRAPHY IN WOMEN - COMPARISON OF PERIURETHRAL AND TRANSVAGINAL APPROACHES

Needle electromyography (EMG) of the striated urethral sphincter is th e only technique that permits detection of individual motor unit actio n potentials (MUAPs) and is a valuable diagnostic tool in the evaluati on of women with urinary incontinence and voiding disorders. The purpo se of this study was to compare two methods of urethral needle EMG wit h respect to the number of MUAPs identified, the amount of patient dis comfort, and the duration of the examination. Twenty consecutive women referred for electrodiagnostic testing to evaluate symptoms of urinar y incontinence and/or voiding dysfunction underwent both methods of th e needle examination in a prospective randomized cross-over study desi gn with each patient acting as her own control. A full cross-over anal ysis was conducted to detect period and sequence effects using analysi s of variance with a power of 0.85 and a significance level of P < 0.0 5. Twice as many MUAPs were identified using the periurethral approach (8.8 versus 3.9) with a mean difference of 5.0 (P = 0.0008). There wa s a non-significant trend to greater patient discomfort with the periu rethral approach; however, the discomfort was generally rated as mild to moderate. The length of time required to count an identifiable MUAP s did not vary significantly between the two methods. We conclude that the periurethral approach is superior to the transvaginal approach wi th respect to the quantity of electrodiagnostic information obtained a nd propose that this method be standardized to characterize more accur ately the neurogenic component of urinary incontinence and voiding dys function for future electrodiagnostic studies. (C) 1998 Wiley-Liss, In c.