Detrusor Overactivity Associated with External Sphincter Dyssynergia

Destrusor overactivity associated with external sphincter dyssynergia is a type of dysfunction seen in those with injuries of the spinal cord affecting the upper motor neurons. In these cases, the actions between the detrusor muscle and the external sphincter is caused by a disruption of the coordinated pathway from the spinal cord above the sacral levels to the pontine micturition centre. Both the detrusor muscle and the external sphincter are overactive due to lack of control and to descending inhibition from the pons and cortex. Instead of a coordinated detrusor muscle contraction and external sphincter relaxation, both contract reflexively when the bladder is stretched during filling. The detrusor muscle becomes overactive, reflexively contracting even with small volumes in the bladder. Detrusor muscle contraction against an overactive external sphincter that obstructs outward flow, results in high bladder pressures. This leads to incontinence (when the detrusor contracts hard enough to overcome the sphincter contraction), incomplete emptying (due to sphincter co-contraction), and reflux (due to high bladder pressures) with resultant recurrent bladder infections, stones, hydronephrosis, pyelonephritis, and renal failure.