Experimental animal investigations for the objectification of bladder sensibility by frequency analysis of EEG-activity and registration of evoked potentials

Purpose: Many neurological diseases are associated with bladder sensibility disorders. The aim of this study was to develop, in animal experiments, a diagnostic tool to improve the objective assessment of bladder afferences. Materials and Methods: Evolted potentials were registered by bladder affere nce stimulation in 6 foxhounds during electrical stimulation of the bladder wall, the complete sacral root and the C- and A delta-fibres and, in 6 rab bits, during repeated bladder filling. Furthermore, the influence of affere nt stimulation by bladder filling and electrical sacral root stimulation on EEG-frequencies was investigated. Results: Evoked potentials during electrical bladder wall stimulation or re peated bladder filling showed maximal cerebral responses:after a latency of 2500-6500 ms after beginning stimulation. Stimulation of the complete sacr al root resulted in maximal responses up to 800 ms and smaller responses up to 3500 ms. During selective stimulation of C- and A delta-fibres, the res ponse up to 800ms was clearly reduced whereas the response up to 3500 ms re mained unchanged. Before afferent stimulation, the EEG-frequency analysis s howed frequencies between 2 and 4Hz. During stimulation,these frequencies ( 2 - 4 Hz) were reduced and frequencies > 8 Hz were observed. After stimulat ion, the frequencies returned to the values bt fore stimulation. Conclusions: We conclude that the registration of evoked potentials with la tencies of > 6500 ms and selective afferent stimulation in necessary for th e evaluation of bladder afferences and that the activation of bladder affer ences results in reversible and reproducible changes in EEG-activity repres enting an increased vigilance.