Intact innervation of the urethra and periurethral muscles is paramount to maintaining continence. Voluntary and reflex stimulation of the muscles of the pelvic diaphragm also occurs, resulting from increased efferent pudendal nerve activity. There are multiple complex facilitative and inhibitory pathways that function under the control of higher centers. Above the level of the spinal cord, the most important facilitative motor center for micturition is the pontine micturition center located in the brain stem.
The cerebellum is the major center for controlling pelvic floor relaxation and the rate and force of detrusor contractions. The basal ganglia are involved in inhibition of detrusor contractions. The cerebral cortex primarily the frontal lobes is important in inhibiting the pontine micturition reflex. A promising area for developing new stress urinary incontinence SUI treatments involves the role of the external urethral sphincter.
The origin of somatic nerves to the external urethral sphincter is Onuf's nucleus in the sacral spinal cord. Researchers hope to develop medications by targeting the neurons of Onuf's nucleus to increase external urethral sphincter tone, thus decreasing incontinence. Brigitte Schurch, Stefano Carda, in Handbook of Clinical Neurology , Reflex bladder function generally occurs in humans after suprasacral cord injury within weeks or months after injury.
Bladder sensation may be somewhat preserved in incomplete lesions but voluntary inhibition of the micturition reflex arc is lost. The initial retention of urine will be followed by neurogenic detrusor overactivity, resulting in a small, hyperreflexic bladder. Dyssynergic contraction of the external sphincter, increased guarding reflex, and impaired detrusor contraction result in inefficient voiding. Overall, reorganization of the central nervous system leads to a high voiding pressure, residual urine in the bladder, and incontinence.
These subsequently might induce recurrent UTI, stone formation, hydronephrosis, and finally renal failure McGuire and Savastano, In incomplete suprasacral lesion, synergistic relaxation of the external sphincter may be preserved. Balanced voiding may occur but urgency and urge incontinence usually persist. Abnormal bladder function can be present in both adults and children with end-stage renal disease ESRD who are transplant candidates but the problem is more prevalent in the pediatric age group.
In some of these conditions, the development of ESRD is frequently a consequence of the congenital anomaly associated with renal dysplasia PUV, PBS, persistence of the cloaca 57, 82, ; however in others, such as NVD, whether congenital or acquired, renal damage results from bladder dysfunction and is preventable with good management. Graham H. Creasey, Michael D. Craggs, in Handbook of Clinical Neurology , Disorders of bladder, bowel, and sexual function cause persistent complications, morbidity, and reduction of quality of life following spinal cord injury SCI.
In spite of a range of medical and surgical interventions and the use of a variety of appliances and devices, many patients are plagued by urinary tract infection and stones, kidney damage, incontinence of urine and feces, constipation, erectile dysfunction, and infertility, with substantial emotional, social, and financial costs.
Functional electrical stimulation has now been used to restore useful bladder, bowel, and sexual function to several thousand patients with SCI and is commercially available in over 20 countries. Further research is in progress to refine these techniques. Ronald F. Pfeiffer, in Handbook of Clinical Neurology , Disordered bladder function is also common in MSA. It may be the initial clinical feature Sakakibara et al.
Both urinary retention and incontinence may occur. Urodynamic and neurophysiological testing also presents a diverse picture; both hyperactive and hypoactive bladder dysfunction occur.