THE EFFICACY OF SACRAL NERVE STIMULATION IN PATIENTS WITH NEUROPATHIC CONSTIPATION

Abstract

Constipation is a common complaint in people with neurological diseases causing significant physical and psychological distress. Poor response to therapy is due to a number of factors: severe disruption to normal physiology (gut denervation); use of constipating drugs in the presence of immobility; and co-existence of faecal incontinence and constipation precluding treatment with standard oral laxatives. Sacral nerve stimulation (SNS) has been shown to have a beneficial effect in patients with functional constipation. It is a treatment with established efficacy for faecal incontinence, including that due to neurological disease. However, there are no studies on the efficacy of SNS in neuropathic constipation. Pilot work in this patient group was positive, thus a formal trial was indicated. This thesis reports a proof-of-concept trial examining the effectiveness of temporary SNS in neurological constipation. The study assessed efficacy over a three-week period of temporary SNS using an off-on-off design. Methods and principal evaluation criteria:
The trial aimed to recruit 30 patients with constipation of neurological origin from the specialist clinic at the University Hospital North Durham, over a two-year period. For each patient, the trial lasted twelve weeks, including: a pre-SNS period of six weeks of baseline assessment, a three week period of stimulation and a three week period of post-treatment assessment. The measurement schedule of symptoms and quality-of-life during the trial assessed symptom stability and the temporal effects of treatment. Physiological data was collected before and during treatment, in the form of transit studies and laser Doppler flow cytometry of rectal mucosal blood supply. The primary outcome measure was a global assessment of severity of constipation. Self-administered questionnaires including patient assessment of symptoms (PAC-SYM) and patient assessment of quality of life (PAC-QOL), transit study, and laser Doppler flowcytometry (LDFC) constituted the secondary outcome measures. Patients responding to temporary SNS were offered implanted permanent SNS and long term response was evaluated.
Results and possible implications:
Twenty-two patients were recruited, including 8 men and 14 women with an average age of 51.5 years (Range 38-69 yrs.). Four patients dropped out and were lost to follow-up; 18 patients completed the trial. Twelve patients (67%) had a successful response after three weeks of bilateral temporary stimulation and underwent permanent implant. The Global Assessment Score for constipation, PAC-SYM and PAC-QOL scores for these patients improved during treatment with temporary SNS (p<0.05). There was also an improvement in toileting time (p=0.04) and decrease in overall laxative use (p=0.03). Physiological parameters did not change. The overall response rate during long-term follow-up (mean 20 mths) was 6/12 (50%, 95%CI: 21% to 79%).
Interpretation:
Short term treatment with SNS helped two thirds of patients with neuropathic constipation in the short term. There was good symptom stability before treatment and rapid return to baseline after treatment. However, there were no improvements in the physiological measures used, so that a placebo response may have brought about the improvement in some patients. Temporary SNS only identified 50% of long-term responders.