Hypothesis / aims of study
Sacral neuromodulation (SNM) is an option for voiding dysfunction (VD) or detrusor overactivity (DO) when conservative treatments have failed. If the patient’s symptoms improve by more than 50% during the test phase, the patient is qualified for the implant. We evaluated the results of the implant in a tertiary referral centre.
Study design, materials and methods
One hundred and forty-one patients who underwent PNE between 2019 and 2024 were prospectively collected. Gender, age, diagnosis (VD or DO), psychiatric condition, adverse events (AEs), and implant success were analysed. Fisher exact and logistic regression tests were used for statistical analysis with R studio program.
Results
Of 141 patients, 126 (89.4%) were female and 15 (10.6%) male, with a median age of 47.8(16-80). Eighty-two (58.2%) had a diagnosis of VD and 59 (41.8%) DO. Sixty-eight patients (48.22%) were deemed to have successful PNE. There was no correlation between PNE success and gender (p=0.102) or diagnosis (VD n=41, DO n=27; p=0.619). There was no statistically significant association between psychiatric comorbidity and the distribution of VD and DO (p=0.834), but there was a strong correlation between PNE success and reported psychiatric comorbidity (p<0.001). Logistic regression analysis demonstrated that increasing age was associated with treatment failure with OR 0.97(0.95-0.99, p=0.003) with age cut off at 50% probability being 45.1(AUC 0.645).
Of those who received the permanent implant (Sixty-eight patients (48.22%)) we found sixty-four females (94.1%), and four males (6.9%). Five patients were excluded as they had less than 6 months of follow-up. Median patient age was 46 (SD 16.4). Thirty-nine (61.9%) had diagnosis of VD and twenty-four (38.1%) DO. In fifty-one (81%) patients, the implants worked well according to the patient's subjective assessment. In 15 patients, pain was the main AE. The second implant was done in two patients who developed an infection, three patients whose battery was flipped, and one patient who changed to a rechargeable device. In twelve (19%) patients, the implant did not work. The main reason was pain with three devices removed. There was no statistical correlation between SNS success and diagnosis type (p=0.510) or psychiatric comorbidity (p=0.110). There was no association between patient age and treatment outcome (B=-0.019, SE=0.021, p=0.375).
Interpretation of results
The study results demonstrated that the psychiatric state of the patients was a contributing factor to their positive response to PNE. The age of the patients is another factor that must be taken into account when selecting subjects for the study. The findings revealed that patients below the age of 45 exhibited a more favourable response to PNE.
About the diagnostic process, whether for PNE or permanent implant, no differences were observed between DO and VD. However, a distinction emerged in terms of gender, with females demonstrating a more favourable response to both PNE and permanent implant.
Concerning complications, only two patients developed an infection. Throughout the procedure, gentamicin coverage is maintained (the battery is stored in a gentamicin-filled jar and the wires are covered with gentamicin gauze throughout), along with intravenous gentamicin or intravenous antibiotic therapy, based on the patient's characteristics before surgery. Besides, an antibiotic for home, typically co-amoxiclav, for 7 days.
The primary adverse event is pain, particularly in the battery pocket. This has been attributed to weight fluctuations in the patients. Consequently, a BMI cut-off point of 35 is utilised to determine the suitability of patients for PNE and permanent implant procedures. Patients are advised to undergo a reduction in weight and achieve a BMI within the acceptable range prior to undergoing the procedure.