Electromyographic study of the striated urethral sphincter by using the bulbocavernosus reflex: Study on change of sacral reflex activity caused by bladder filling

(Purpose) The change of sacral reflex activity of the striated urethral sphincter in the urine storage phase is investigated using evoked potential reaction of the bulbocavernosus reflex (BCR). (Methods) Eleven normal male subjects and 13 male patients with neurogenic bladder due to suprasacral (C3∼C7) spinal cord injury (SCI patients) were investigated. Within the SCI patients, five were complete SCI and 8 were incomplete SCI. BCR was elicited by electrical stimulation of dorsal nerve of the penis, and the evoked potential of the BCR was recorded with a concentric needle electrode from the periurethral striated muscle. BCR was performed both at empty and at filled bladder respectively, and changes of the amplitudes (AMP) were examined. Moreover, the changes of AMP affected by bladder filling were compared between the normal subjects and the SCI patients. (Results) In both the normal subjects and the SCI patients, AMP increased at the filled bladder as compared with that of the empty bladder. In addition, the change of AMP was statistically bigger in the SCI patients (a ratio of amplitude at filled bladder/amplitude at empty bladder: 4.73 ± 3.90) than in the normal subjects (the ratio: 1.32 ± 0.44). (Conclusion) Sacral reflex activity was accelerated by bladder filling in both the normal subjects and SCI patients. And the acceleration in the SCI patients was more remarkable than that in the normal subjects. In addition to the conventional evaluation of the integrity of sacral reflex arc by BCR examination, the observation of changes of BCR affected by bladder filling may provide the information for the continuity of sacral segment and supraspinal micturition center.