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