Functional brainstem changes in response to bladder function alteration elicited by surgical reduction in bladder capacity: a functional magnetic resonance imaging study

Abstract

Purpose: Our previous results revealed a positive correlation between bladder dysfunction and cortical arousals in children with enuresis. This finding implied an interrelationship between bladder dysfunction and brainstem dysfunction. Thus, we used an animal model to characterize brainstem functional changes in response to altered bladder function.

Materials and methods: Adult male New Zealand rabbits weighing 3.0 to 3.5 kg underwent surgical bladder volume reduction (12) or sham operation (12). We performed conventional fill cystometry and brainstem functional magnetic resonance imaging in each group 4 weeks postoperatively. During scanning bladder stimulation was provided by bladder filling up to 70% of maximum capacity. We then compared brainstem activation area(s).

Results: Results revealed voiding dysfunction in animals with altered bladder function. Bladder function was markedly altered in the reduced bladder volume vs the sham operated group, mainly as significantly increased maximum voiding detrusor pressure (mean ± 1 SD 24.4 ± 7.0 vs 0.16.5 ± 7.2 cm water, p <0.05) and markedly decreased cystometric bladder volume (mean 35.3 ± 8.2 vs 71.6 ± 12.9 ml, p <0.05). Functional magnetic resonance imaging results revealed activation of 2 brainstem regions, including in 1) the ventrolateral periaqueductal gray and 2) the dorsolateral pons, in response to bladder distention. Activation in the ventrolateral periaqueductal gray was significantly decreased in the reduced bladder vs the sham operated group with a corresponding decrease in signal size (25% vs 83.3%, signal size 0.7 ± 1.4 vs 3.3 ± 2.1 mm(2)). There was no significant difference in activation of the dorsolateral pons between the groups (83.3% vs 91.7%, signal size 3.7 ± 2.4 vs 0.4.7 ± 3.0 mm(2)).

Conclusions: Functional derangement in brainstem micturition centers can be evoked by bladder dysfunction. In response to bladder dysfunction the ventrolateral periaqueductal gray shows deactivation during bladder distention, suggesting that it has an important role in bladder dysfunction biofeedback.