Cerebral control of the bladder in normal and urge-incontinent women

Abstract

Aim: To identify age-related changes in the normal brain/bladder control system, and differences between urge incontinence in younger and older women, as shown by brain responses to bladder filling; and to use age, bladder volume, urge incontinence and detrusor overactivity (DO) as probes to reveal control-system function. Functional MRI was used to examine regional brain responses to bladder infusion in 21 females (26 -85 years): 11 "cases" with urge incontinence and DO (proven previously) and 10 normal "controls". Responses and their age dependence were determined at small and large bladder volumes, in whole brain and in regions of interest representing right insula and anterior cingulate (ACG). In "controls", increasing bladder volume/sensation led to increasing insular responses; with increasing age, insular responses became weaker. In younger "cases", ACG responded abnormally strongly at large bladder volumes/strong sensation. Elderly "cases" showed strong ACG responses even at small bladder volume, but more moderate responses at larger volumes; if DO occurred, pontine micturition center (PMC) activation did not increase. Conclusion:Among normal "controls", increasing age leads to decreased responses in brain regions involved in bladder control, including right insula, consistent with its role in mapping normal bladder sensations. Strong ACG activation occurs in urge-incontinent "cases" and may be a sign of urgency, indicating recruitment of alternative pathways when loss of bladder control is feared. Easier ACG provocation in older "cases" reflects lack of physiological reserve or different etiology. ACG responses seem associated with PMC inhibition: reduced ACG activity accompanies failure of inhibition (DO).

CNS and bladder (short review for clinicians)

“…Such activation appears to be significantly stronger in incontinent subjects during reported urgency albeit decreasing with advanced age (9,12).…”

“…In addition, fMRI studies have shown that the PMC responds to bladder filling during the storage phase as well (both in normal subjects and in urge incontinent subjects prior to onset of detrusor overactivity, DO) (8)(9)(10). Thus imaging studies indicate that PMC responses during the storage phase represent inhibition of the PMC and the voiding reflex.…”

“…A group from the University of Pittsburgh (Geriatric Continence Research Unit) has published several studies on older women with urgency incontinence describing regional brain activity during urgency (8,9,17,23). Such activity encompasses abnormally strong activations in the SMA, dACG, insula and dlPFC, together with deactivations in the ventromedial cortex and parahippocampus (see Figure 5).…”

Mental disorders in children and adolescents with lower urinary tract dysfunction

“…11 Yang et al 12 compared children with ADHD to children with ADHD and enuresis, and observed the latter had shorter response times in neuropsychological tests devised to assess attentional performance, revealing they had less inhibitory control. Understanding this pathophysiological correlation and the importance of treating psychiatric comorbidities are key steps lower urinary tract dysfunction: 56% of the children postponing voiding had clinical-range scores in the CBCL versus 24% of the children with urinary incontinence.…”

Diagnosis and Treatment of Overactive Bladder

“…These afferent signals activate sympathetic pathways in the hypogastric and pudendal nerves, which lead to contraction of the smooth and striated sphincters, and at the same time inhibit detrusor contraction. In addition, high cortical centers are activated, (Griffiths et al, 2007), and stimulate the storage center in the pons. (Fowler et al, 2008) When further bladder filling leads to increased afferent signaling from the bladder, spinobulbospinal reflex pathways are carried via the pelvic nerve and spinal cord to the pontine micturition center, which activates parasympathetic pathways that cause bladder contraction and inhibit sympathetic and pudendal contraction of the sphincter (Fowler et al, 2008) For coordinated micturition to occur, parasympathetic stimulation of the detrusor occurs via cholinergic muscarinic receptors.…”