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Why do patients fail peripheral nerve
evaluation?
Vicki Patton David Z. Lubowski
Department Colorectal Surgery
St George Hospital and University of NSW
Sydney Australia
Sacral Nerve Stimulation
Testing phase success defined as ..
• Greater than 50% improvement in
incontinent episodes (Melenhorst et al. 2007)
• Patient-reported improvement in
bowel control (Ganio et al. 2001)
• Improvement in quantitative
measures (Matzel et al. 2011)
Factors associated with PNE failure
• Increased motor threshold
at time of implant (Dudding et al 2008)
• Advanced age (Gaucerol et al 2007)
• Repeating the test phase (Dudding et al 2008)
• Use of non-tined lead (Altomare et al 2011)
Aims of study
• Examine the clinical and physiological characteristics of the PNE fail group
• Compare PNE fail patients with those who progress to SNS
• Identify characteristics predicting PNE failure
• What happens to those who fail PNE?
Methods
• Review prospective clinical notes taken by treating surgeon to identify primary presenting symptom
o Urgency: unable to defer for 10 minutes
o Involuntary soiling: without awareness
• Anorectal physiology studies
o Baseline St Mark’s continence score
o Anal manometry
o PNTML
o Endoanal ultrasound
Methods – PNE technique
• Under sedation in operating theatre
• Unipolar temporary lead inserted
• S3 or S4 used dependent on motor response at
lowest threshold
• Secured externally and left in for minimum 3 weeks
Types of PNE failure • Technical fail: absent stimulation perception due to
equipment failure
• Clinical fail: continued stimulation perception
without clinical improvement
140 PNE inserted
102 PNE success
38 PNE Fail
7 technical
Fail
31 clinical Fail
Results
Results
PNE Success n=102
PNE Fail n=31
Significance
Mean Age:
63.2
64.1
p = 0.71
Gender: - Male - Female
7 (6.9%) 95 (93.1%)
2 (6.5%) 29 (93.5%)
p = 0.94
Internal sphincter: -Intact -Defect
82 % 18 %
67 % 33 %
p = 0.09
External sphincter intact or defect
OR 3.95 p=0.006
(95%CI 1.43,10.93)
88%
67%
12%
33%
Location of PNE
PNE success or fail
S3 p = 0.269
S4 p = 0.106
S3 & S4
p = 0.612
Anorectal physiology &
baseline St Mark’s score: Results
Mean score PNE Success
PNE Clinical
Fail
95% CI Difference
In mean
P
St Mark’s Score (0-24) 14.15 13.04 -0.94 , 3.114 0.29
Max resting (cmH20) 54.10 55.21 -1.39 , 3.62 0.37
Max squeeze(cmH20) 76.04 76.24 -21.85 , 28.65 0.79
Max Cough (cmH20) 98.34 103.50 -25.86 ,15.54 0.62
HPZ (cm) 1.96 2.00 -0.53 , 0.44 0.86
PNTML(R) msec 2.12 2.17 -0.26 , 0.15 0.61
PNTML (L) msec 2.09 2.24 -0.37 , 0.06 0.16
AMS Upper mAmps 12.84 13.80 -3.99 , 2.06 0.53
AMS Mid mAmps 8.18 8.78 -2.60 , 1.39 0.55
AMS Lower mAmps 7.93 8.25 -2.19 , 1.55 0.74
PNE success or fail Primary symptom: urgency / soiling
OR 6.071 p<0.001
95% CI (2.52,14.61)
Presenting Symptom
Total
PNE
success PNE fail
Urgency Count 85 14 99
% within Urgency 85.9% 14.1% 100.0%
Soiling Count 17 17 34
% within Soiling 50.0% 50.0% 100.0%
Total
Count
102
31
133
PNE success or fail
primary symptom: urgency / soiling
n = 14 n = 17
n = 85
n = 17
OR 6.071 p<0.001
95% CI (2.52,14.61)
Regression analysis: Binary: PNE Fail Yes or No
o Anorectal physiology results
o Incontinence severity at baseline
o Ultrasound sphincters (intact or defect)
o Primary presenting symptom (urgency or soil)
o Location of PNE insertion
Intact external sphincter and primary presenting
symptom of urgency were predictive of PNE success
(p<0.001)
140 PNE inserted
99 PNE success Progressed
to SNS
12 straight to SNS
111 SNS
38 PNE Fail
4 Chait caecostomy
1 graciloplasty
7 technical
Fail
31 clinical Fail
1 redo PNE tined lead (fail)
32 conservative management
2 sphincter
repairs
Outcome of PNE
3 PNE success
not progressed
to SNS
Conclusions
• Technical fails with PNE can be avoided with attention to securing the lead
• Presenting with the clinical symptom of urgency as opposed to soiling is significantly predictive of a successful PNE
• Most patients who fail PNE continue using conservative methods to manage incontinence
• PNE fail pts continue to present for follow-up suggesting dissatisfaction with conservative ways of managing FI