Brain control of normal and overactive bladder

Bladder control problems are common but their cause is often unclear. Many investigators have sought causes in the lower urinary tract, but fewer in the supraspinal control system. We have used functional magnetic resonance imaging (fMRI) to determine brain responses to bladder filling in subjects with normal and with poor bladder control (detrusor overactivity).

Cerebral responses to bladder infusion were recorded in 1 male and 11 females without overt neurological abnormality, aged 26 to 83 years. Six had good bladder control and 6 had poor control on prior urodynamics. fMRI was performed while repeatedly infusing and withdrawing liquid into and out of the bladder, and monitoring intravesical pressure. Measurements were made at small and large bladder volumes.

fMRI detected activation of many brain regions involved in bladder control, including periaqueductal gray, thalamus, insula, dorsal anterior cingulate, and ventromedial cerebellum. Orbitofrontal cortex, pontine micturition center and preoptic hypothalamus were visible in subgroup analyses. Activations outweighed deactivations and responses became stronger at large bladder volumes. Among subjects with good control, this strengthening of response was prominent in the orbitofrontal cortex. Among those with poor control cortical responses were exaggerated at larger bladder volumes, except in the orbitofrontal cortex, which remained weakly activated. This difference was not due to concurrent detrusor activity.

Poor bladder control is specifically associated with inadequate activation of orbitofrontal cortex. Clinically, frontal cortical lesions cause bladder control problems. This study suggests a similar neurophysiological basis for poor bladder control in the absence of overt neurological lesion.