Current perception thresholds in the lower urinary tract: Sine- and square-wave currents studied in young healthy volunteers.

AIMS

To establish normative current perception threshold (CPT) values with neuroselective sine-wave current in the lower urinary tract and to compare these values with square-wave current CPTs.

MATERIALS AND METHODS

10 female and 8 male healthy volunteers were used for this study. A filling cystometry was performed and CPTs were determined with square-wave current at a frequency of 2.5 Hz and with neuroselective sine-wave current at 5 (C-fiber), 250 (Adelta-fiber), and 2000 Hz (Abeta-fiber) in the bladder, the posterior, and the distal urethra.

RESULTS

Bladder CPTs were significantly higher compared with CPTs in the posterior urethra (P < 0.028) and in the distal urethra (P < 0.002) with all three sine-wave frequencies. No significant difference was found with any sine-wave frequency between the posterior and distal urethra (P > 0.30). Using square-wave pulses at 2.5 Hz, CPTs decreased towards the distal urethra, with a significant difference between the three stimulation sites (P < 0.0001). At all sites tested, the CPT's determined with sine-wave current at 2000 Hz were significantly higher than those at 250 Hz (P < 0.002) and 5 Hz (P < 0.001). No significant difference was found between 5 Hz and 250 Hz at any site in the LUT (P > 0.50). At all sites, CPTs determined with square-wave pulses at 2.5 Hz were significantly higher than those determined with sine-wave current at all frequencies (P < 0.001). CPTs determined with all sine-wave currents were not correlated with CPTs using square-wave pulses. There was no correlation between the volumes at which sensation of filling occurred and the CPTs.

CONCLUSIONS

We described normative values in young healthy volunteers at three sites in the LUT using sine-wave current. Although this type of current is said to be neuroselctive, this needs to be confirmed. Stimulation with sine-wave current is different and might be more physiologic compared to square-wave stimulation. Our data show that sine-wave current stimulation at 5 Hz, 250 Hz, and 2000 Hz can probably not be used as a semi-objective measurement of the sensation of bladder filling because no correlation was found between CPTs and the cystometeric sensation of filling.