Use of functional imaging to monitor central control of voiding in humans.

Bladder problems are frequently disorders of control, which is exercised from the brain. In such disorders, brain responses to bladder events are abnormal; therapy is accompanied by regional changes that may be measured by functional imaging and used to monitor the effect of treatment. The regional responses may be understood in terms of a tentative model of the bladder control system. The model helps also to interpret alterations in brain behavior (as imaged by functional scanning) that occur when afferent signals from bladder or urethra are changed experimentally or by an underlying disorder or treatment, for example, overactive bladder (urge/urgency incontinence). Successful treatment may either increase the ability to cope with the problem or may be curative. The direction of treatment-induced change of abnormal brain responses can distinguish these two possibilities and shed light on the therapeutic mechanism. In addition, brain activity in regions such as insula or dorsal anterior cingulate cortex may be regarded as a proxy for sensations such as desire to void or urgency, which are otherwise difficult to define or measure. Monitoring of brain responses in these regions offers an obvious way to test the effect of drugs.