INTRODUCTION: The purpose of the study was to build and test a mathematical model that allows new information about efferent neural activity for the bladder and sphincter to be extracted from urodynamic recordings during the micturition cycle.
METHODS: The main features of the VBN micturition model were reviewed. An extended VBN model that includes a more detailed model of nervous control was then described. The mean firing rate F(t) of efferent neurons was linked first to an effective calcium excitation E(t) in the muscle cells and then to the detrusor and urethral pressures. Finally, this model was used to retrospectively analyze urodynamic recordings of 166 male and female patients with various voiding characteristics.
RESULTS: The main result was the striking simplicity of the computed F(t) curves for both the detrusor and sphincter during the 3 phases of the micturition cycle (storage-continence, micturition, and return to continence). This result occurred in most of the micturitions: (1) normal with or without break of detrusor excitation, (2) abnormal with large residual volume, (3) abnormal with effect of a urethral catheter in situ. These curves F(t) were found as a sequence of constant values during the onset of flow and during the plateau phase, and then as a decreasing exponential during the return to continence phase. The transition between the 2 phases was always brisk, suggesting ON/OFF switching of reflexes.
CONCLUSION: The extended VBN model for analyzing urodynamic recordings facilitates comparison and discussion of successive micturitions from a given patient and is a valuable complement to animal studies and to functional imaging of the human brain.
Françoise A Valentini, Leonor Mazières, Pierre P Nelson
Submitted April 15, 2010 - Accepted for Publication June 13, 2010
KEYWORDS: Mathematical modeling; Nervous control; Micturition; Urodynamics.
CITATION: Urotoday Int J. 2010 Aug;3(4).