Electromyography of urethral sphincter in women with urinary retention.

Concentric-needle electromyography (EMG) of the urethral sphincter muscle was carried out in 48 women with urinary retention. Changes in motor unit configuration indicating reinnervation were found in 16 women, and myotonic-like EMG activity, which may impair urethral relaxation, in 19 women. Sphincter EMG was normal in 13 cases. The finding of a significant abnormality in 72% of cases calls into question the validity of the commonly applied diagnosis of psychogenic urinary retention.