1973 Volume 64 Issue 4 Pages 307-314
Since spring of the year 1970 we have made observations of movements of the vesical neck during urination by means of x-ray television mainly in patients with damage to the spinal cord. By a simultaneous electromyographic study of striated muscles of the pelvic floor we have also investigated functional interrelation between the vesical neck and these striated muscles.
As a result, not a few of these patients were found to have a vesical neck of a peculiar shape (called “constricted type” by us tentatively). This unusual shape (hence motility) of the vesical neck is supposed to be due not to functional causes but to organic ones including atrophy of the prostate and sequelae of inflammation of the posterior urethra, is considered, from a hydraulic standpoint, to be a potential impediment to conveyance of signal of intravesical pressure to the external sphincter and hence to resultant opening of the sphincter and of initiation of micturition, and could thus be deemed as an indication for TUR.
Contrary to the dominant concept of the physiologic mechanism of urination that elimination of inhibitory control over contraction of the detrusor and voluntary relaxation of the external sphincter (though which of these 2 phenomena precedes the other is a matter that remains to be ascertained) initiate urination, our electromyographic study of muscles of the pelvic floor and periurethral muscles of patients with spinal cord injury during micturition showed that spikes emerging on EMGs of these muscles were attenuated or disappeared en bloc immediately before passage of urine in many instances, although such patients were mostly incapable of voiding voluntarily. These findings point definitely to an essential role played relaxation of muscles involved, occurring as a reflex activity in the mechanism of urination and may be interpreted as indicating that persons with the normal power of voiding can get both detrusor reflex and relaxation reflex of the striated muscles under control.
