[The striated sphincter of the urethra. 2: Specific methods for studying the striated sphincter of the urethra]

Radiology and electromyography of the lower urinary tract are specific techniques for exploration of the urethral rhabdosphincter. Retrograde and mictional urethrography provide data on the extent of the membranous urethra. In the presence of rhabdosphincter lesions a mictional urethrogram is often sufficient to establish a diagnosis from the direct and indirect signs of obstruction it supplies. A retrograde urethrography examination can be added validly to the previous exploration to improve precise definition of sclerosis: in contrast it is indispensable when miction is impossible. Differential diagnosis between spasm and stenosis of striated and dyssynergy of smooth muscle sphincter is by pharmacologic tests. Radiologic study of sphincter contraction is generally by cineradiography with arrest of miction. Results are limited, however, when compared with those of a radiodynamic study: the latter supplies information on the functioning of the para- and peri-urethral rhabdosphincter, and allows measurement of contraction. The electromyogram, with its different practical technical modalities, provides details of the urethral rhabdosphincter. The contact electromyogram gives quantitative data but fails to diagnose a neurological lesion. It analyzes behavior of the sphincter in its para-urethral part and can localize its diaphragmatic portion; dynamic electric profiles are of little reliability, in contrast to static profiles which quantify electric activity at all points in the urethra during the same contraction. The standard percutaneous needle electromyography examination provides qualitative data on the peri-urethral rhabdosphincter, but lacks precision as to the region explored, while qualitative information on the para-urethral sphincter requires the use of an endo-urethral approach. A difference in potential between para- and peri-urethral musculature has been demonstrated a fact confirmed by anatomical findings in Goslings study. In normal subjects, the rhabdosphincter differs from other skeletal muscles by its constant activity except during miction; potentials in children differ from those in adults by their duration. In lower motor neurone disease signs of denervation appear after several weeks, while in upper motor neurone affections the potentials are normal but nociceptive and bulbocavernous stimuli provoke bursts of hyperactivity which reappear very shortly after the paraplegia. Striated muscle fibrosis provokes peripheral signs with persistence of regions of increased reflexes. Tests of responses to stimuli provide important information enabling the site of the neurogenic lesion to be determined.