Evaluation of sacral neuromodulation system with new six-contact points electrode in pigs

We investigated the effects of sacral neuromodulation using the new six-contact electrode vs the four-contact electrode in pigs.

Randomly, a six-contact electrode was implanted in eight pigs in one side of the third sacral (S3) foramen, and a four-contact electrode was implanted in the other side using the same method. Using an external neurostimulator, the number of contact points (sensitive voltage ≤ 2 V) of both electrodes (SacralStim and InterStim systems) was calculated. Cystometry was performed by infusing normal saline or acetic acid. Then sacral neuromodulation with the SacralStim and InterStim systems was induced at a voltage at which we could observe perianal and/or tail movement. Multiple cystometrograms were performed to determine the effects of the two systems on the micturition reflex.

The mean number of sensitive points of six-contact electrodes of the SacralStim system (2.63 ± 0.32) was higher than that of the quadripolar-lead electrodes of the InterStim system (1.38 ± 0.18), and the difference was statistically significant (P < 0.05). Acetic acid-induced bladder overactivity significantly reduced bladder capacity to 54.89% ± 4.7% of the normal saline control level. During acetic acid infusion, sacral neuromodulation with the SacralStim system suppressed bladder overactivity and significantly increased bladder capacity to 70.41% ± 5.4% of the normal saline control level, compared with the acetic acid level ( P < 0.05). Moreover, sacral neuromodulation with the InterStim system also significantly increased bladder capacity to 69.63% ± 5.3% of the normal saline control level, compared with the acetic acid level ( P < 0.05). No significant differences were found in the results obtained using the two systems ( P > 0.05).

The six-contact electrode of the SacralStim system had more sensitive points (<2 V) than that of the quadripolar-lead electrode of InterStim system. Potentially, it has more postimplantation programming options and battery savings manifested by lower voltage will increase the longevity of the stimulator. Further studies of sacral neuromodulation with six-contact electrodes in clinical practice are needed.