Temporal summation to thermal stimuli is elevated in women with overactive bladder syndrome

Abstract

Introduction: This study sought to provide a preliminary assessment of whether spinally mediated afferent hyperactivity (i.e., central sensitization) might contribute to manifestations of overactive bladder syndrome (OAB) in women as indexed by elevated temporal summation of evoked heat pain stimuli.

Methods: We recruited 20 adult women with OAB who were planning to undergo interventional therapy for OAB with either onabotulinumtoxinA injection or sacral neuromodulation and 23 healthy controls without OAB symptoms to undergo quantitative sensory testing with cutaneous thermal pain temporal summation. The primary study outcome was the degree of temporal summation, as reflected in the magnitude of positive slope of the line fitted to the series of 10 stimuli at the 49°C target temperatures. Linear regression and analysis of covariance were utilized to compare the degree of temporal summation between study groups.

Results: The standardized slope of temporal summation trials for women with OAB was significantly higher than for controls (β = 3.43, 95% confidence interval = 0.6-6.2, P = 0.017). The adjusted means ±SE of the standardized temporal summation slopes for the full OAB and control groups were 3.0 ± 0.5 (95% confidence interval = 2.0, 4.1) and 1.7 ± 0.5 (95% confidence interval = 0.7, 2.7), respectively.

Conclusion: In this preliminary study, we demonstrated that women with OAB refractory to primary and secondary therapies exhibited greater thermal cutaneous temporal summation than women without OAB symptoms. This suggests that central sensitization, indexed by temporal summation, may be an underlying factor contributing to OAB in some women. Neurourol. Urodynam. 36:1108-1112, 2017. © 2016 Wiley Periodicals, Inc.

Keywords: OAB; central sensitization; overactive bladder syndrome; quantitative sensory testing; temporal summation; wind-up.

Figure 1

Adjusted mean slopes fitted to VAS pain ratings during temporal summation trials at 49° C for women with OAB and Controls. Women with OAB demonstrated a greater degree of temporal summation than Controls as represented by a higher slope (3.0 vs. 1.7, p = .017).

Figure 2

Comparison of means of temporal summation slopes for controls, women with OAB, and a subset of women indicating a self-reported history of IC/BPS. Bar represents the adjusted mean slope and spike the 95% confidence interval. Significant differences (p < .03) from controls indicated by the asterix.