Hypothesis / aims of study
In urology, sacral neuromodulation (SNM) is used in patients with treatment-resistant voiding or pain symptoms. Patient selection for SNM is essential and patients should be realistically informed about potential benefits of the treatment. Aim of this study was to assess factors associated with permanent SNM device placement and subjective positive clinical outcome in male patients.
Study design, materials and methods
Male patients with SNM testing phase between January 2005 and February 2018 in Tampere University Hospital were accepted to study. Patient files and surgical reports were analyzed for implantation details, disease history and clinical outcome. The study was approved by the ethical committee of the institution.
Patient demographics were obtained including age, illnesses, smoking history, disease history, symptoms and duration of symptoms, prior pharmacological, intravesical and surgical treatments and indication for SNM. Precise procedural data was obtained from SNM testing and permanent SNM device implantation surgeries.
Indication for SNM was classified in four categories: ‘urge’ including urgency-frequency syndrome and incontinence , ‘retention’ including detrusor sphincter dyssynergia (DSD) and non-obstructive urinary retention, ‘pain’ including chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) and interstitial cystitis/bladder pain syndrome (IC/BPS) and ‘mixed’. All patients were refractory to conservative treatments or could not tolerate the side effects. Indication for permanent InterStim® II neuromodulator placement was considered over 50% improvement in symptoms.
Patients who received the permanent SNM device were included in long-term follow-up. Follow-up data included patients’ subjective response, response to symptoms (over 50% improvement meaning significant response), explantations, re-operations and duration of response. Subjective response was noted when patients’ symptoms were completely disappeared or symptoms were satisfactory to patient. Patients were included in follow-up until last check-up, explantation of SNM device or death.
Results
During the study period, 135 tined lead SNM testing phases were performed in 116 patients. Stimulator leads were implanted in 134 of testing operations (99%). Mean age was 52 (±16.2) years and median duration of symptoms was 6.5 (1-39) years. More than one SNM testing phase (in order to apply different electrode position) was done in 15% (17/116) patients. All patients were tested using the tined lead technique.
Permanent InterStim® II device was placed in 42% of the patients. Of the patients with permanent SNM device, 92% had positive subjective response with median duration of 4.4 (0.2-13.7) years. Response was still ongoing in 71% of the patients.
Permanent device implantation rates and positive clinical response rates were 38% and 93% in patients with urgency-frequency syndrome/incontinence, 47% and 93% in patients with DSD or urinary retention and 59% and 61% in patients with pain indication (IC/BPS or CP/CPPS) respectively.
Motoric responses (bellows and toe flex response) were associated with positive subjective clinical response (p=0.049 and 0.042 respectively). Location of stimulator lead (S3 or S4), implantation site (right, left or bi-lateral) or anesthesia modality was not associated with placement of permanent device or clinical response. Explantation rate was 28% and the most common reason was diminished response (in 63% of explantations).
Interpretation of results
Overall nine out of ten patients who receive permanent sacral neuromodulator, benefit from SNM and responses seem to maintain even in long-term follow-up. Patients with pain as an indication for SNM seem to have less benefit from the permanent device compared to other indications. Motoric responses during the test phase were associated with positive subjective clinical response.