BERKELEY, CA (UroToday.com) - In the past, many attempts to understand the mechanisms of action of sacral nerve stimulation (SNS) have been made. The more recent studies, conducted mostly in the urological field, have focused on the central effects of stimulation of the sacral roots.
Our study is based on the hypothesis that SNS could have some effects on the central level by promoting a “setting-up” of a neuronal network between the peripheral and central nervous system involved in attention and control of the continence. This neuroplasticity may allow memorization and re-learning of the mechanisms involved in the control of continence.
To test this hypothesis, we prospectively evaluated 19 patients (17 women) aged between 35-70 years, affected by fecal incontinence, with or without urinary incontinence, and successfully treated with SNS for at least one year.
We switched their stimulator off in order to evaluate the effects on continence by comparing the data recorded at last follow up, those before entering in the study, (stimulator on), and data recorded with the stimulator off. Each patient was evaluated after the first month and every 3 months, or on an as-needed basis, until at least one year. At each visit, disease-specific questionnaires (Wexner score, AMS, ICIQ-SF) and quality of life questionnaire (FiQol) were administered. Incontinence episodes were also recorded relying on the bowel diaries completed by the patients. The results of our study suggest that the effects of SNS are maintained, at least in the short term, in about half of patients when the stimulator is turned off. No statistically significant differences in the score values and number of episodes of incontinence were demonstrated during the “off period" compared with data recorded in the "on period,” although a trend in deterioration of the continence became evident over time. The remaining patients lost the therapeutic efficacy after a median time of 3.4 months (range 0.9-13.5). No factors predictive of symptom recurrence were identified, although at univariate analysis, the idiopathic etiology, higher Wexner and ICIQ scores, and the presence of urinary incontinence showed higher hazard ratios.
Six of 10 patients who had their stimulator reactivated for symptom recurrence were re-evaluated after at least one month: the number of episodes of major fecal incontinence per month was higher, but the scores of incontinence and quality of life were not significantly different when compared with data recorded during the “on period.” The incomplete recovery of continence after reactivation of the electrical stimulus could be explained by only a partial reactivation of the neural pathways developed under chronic SNS.
Despite the fact our study has some limitations due to the small simple size, the short follow-up, and the heterogeneity of patients examined, these data support the hypothesis that a long-period of sacral electrostimulation may induce a brain neuroplasticity for the mechanisms involved in the control of continence, and that in some of these patients, this may become permanent.
Written by:
Giannini Ivana, MD and Altomare Donato Francesco, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Emergency and Organ Transplantation, University Aldo Moro of Bari, Bari, Italy
The effects of sacral nerve stimulation are temporarily maintained after turning the stimulator off - Abstract
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