1. Predictors of Longterm Sacral Nerve Stimulation Failures
Kevin M Zeeck MD1, Morgan Schubbe BS1, Robert C O’Connor MD1, Anjishnu Banerjee PhD2, and Michael L Guralnick MD1
Department of Urology1, Division of Biostatistics2
Medical College of Wisconsin, Milwaukee Wisconsin, USA
Introduction
Sacral nerve stimulation is an accepted treatment option for refractory over active bladder (OAB) and nonobstructive urinary retention (UR). Over time, some patients have return of symptoms despite a functioning SNS implant with reported failure rates of 29% in OAB patients1 and 14% in UR patients.2 Our objective is to identify predictors for which patients have symptomatic failure despite a functioning SNS implant.
Methods
This is an IRB-approved retrospective chart review of patients who underwent SNS for the management of refractory voiding dysfunction. Data collected included: primary indication for SNS (over active bladder (OAB) and urinary retention (UR)), presence of mixed urinary incontinence (MUI), hypersensate bladder (HB), and detrusor overactivity (DO) on urodynamics, as well as demographic variables including age, sex, diabetes, prior pelvic/incontinence surgery, and neurogenic disorder/spine surgery. Patients who had successful test stimulation and implant were analyzed. We then compared patients who had ongoing symptom improvement (long term success) to those who failed (failure of SNS was defined as return of symptoms despite a functioning system) using cox regression analysis.
Results
140 patients analyzed, mean follow up time of 46 months
89/140 (64%) had ongoing symptom improvement
51/140 (36%) had loss of efficacy over time despite a functioning implant (mean 42.8 months {range 2-109})
SNS Efficacy Durability
Success (N=89)
Failure (N=51)
Univariate Analysis (P-Value)
Age
50.1
48.3
0.51
Female
88%
87%
0.92
Depression or Anxiety
55%
45%
0.26
OAB
81%
82%
0.83 UR
19%
20%
0.94
MUI
30%
27%
SUI Surgery
18%
14%
Urge Incontinence
51%
0.50
Smoking
44%
47%
0.71
Diabetes
21%
0.43
Interstitial Cystitis 9%
15%
0.61
Prior Hysterectomy
40%
33%
0.40
Prolapse Surgery
12%
10%
0.64
Neurological History
16%
0.11
Spinal Disease
31%
0.12
Underwent Revisions
42%
53%
0.97
Revisions in first year
0.29
Hypersensate Bladder
36%
0.35
Detrusor Overactivity
34%
49%
0.06
All Patients
UR Patients
OAB Patients
Multivariate Analysis
(P-Value)
Hazard Ratio
Female
0.21
0.51 (0.2 – 1.5)
Depression or Anxiety
0.07
1.75 (0.95 – 3.26)
OAB
0.01
0.30 (0.1 – 0.75)
Prior Hysterectomy
0.02
0.44 (0.22 – 0.87)
Neurological History
0.002
2.9 (1.5 – 5.8)
Spinal Disease
0.26
1.4 (0.8 – 2.7)
Underwent Revisions
<0.001
0.49 (0.33 – 0.72)
Revisions in First year
2.7 (1.3 – 5.7)
Detrusor Overactivity
0.10
0.1 (0.9 – 3.6)
On multivariate analysis:
Predictors of failure:
Underlying neurological conditions and
Need for revision in 1st year after implant
Conclusions
36% of patients with SNS patients lost efficacy over time. The presence of an underlying neurologic condition and the need for surgical revision within the first year of implant may be associated with an increased risk of long term failure.
References
White et al. Sacral nerve stimulation for treatment of refractory urinary retention: long-term efficacy and durability. J Urology
Peeters et al. Long-term follow up of sacral neuromodulation for lower urinary tract dysfunction. British Journal of Urology 2014