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PERIPHERAL NERVE FIELD STIMULATION: MIRAGE OR REALITY?Dr Paul Verrills Interventional Pain PhysicianMBBS FAFMM MPainMed FIPPMetro Spinal Clinic, Australia
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Disclosures
Royalties: NIL Shareholder for Clinical Intelligence Pty Ltd Teaching – Consultant (adhoc peer-peer) Nevro Corporation St. Jude Medical Medtronic Arthrocare Mundipharma Spinal Modulation Boston Scientific
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Peripheral Nerve field Stimulation
subcutaneous implantation of percutaneous leads in the
painful areas
electrical field around the activated bipoles
field of paresthesia within the peripheral distribution of pain
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Peripheral Nerve field Stimulation
Theory behind Neuromodulation:
stimulation of large myelinated fibres closes the gate (via spinal cord)
putative inhibitory neurotransmitters thought to be released during
large myelinated nerve fibre stimulation include:
gamma-aminobutyric acid (GABA)
adenosine
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Peripheral Nerve field Stimulation
Scientific challenges: exact mechanism of producing pain relief is poorly understood
lack of prospective randomized clinical studies
no unifying protocol for implantation
confusion in regards to Indications for the PNfS
lack of scientific data on:
adequate lead depth of implant
adequate parameters for implant
stimulation modalities
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Metro Spinal Clinic PNfS lead depth study (2011)
observational study (n = 28) low-back, n = 19 (17 subcutaneous and 2 iliac crest
nerve stimulation)
occipital nerve stimulation, n = 9
influence of (1) electrode depth and (2) electrode
configuration on sensation perception
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Metro Spinal Clinic PNfS lead depth study (2011)
1. Abejón D., Deer T., Verrills P. 2011. Subcutaneous Stimulation: How to Assess Optimal Implantation Depth. Neuromodulation 2011; e-pub ahead of print. DOI: 10.1111/j.1525-1403.2011.00357
2. McRoberts WP., Cairns K. 2010. A Retrospective Study Evaluating the Effects of Electrode Depth and Spacing for Peripheral Nerve Field Stimulation in Patients with Back Pain. North American Neuromodulation Society Meeting, Las Vegas. Poster Presentation.
References
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Metro Spinal Clinic PNfS lead depth study (2011)
Electrode depths were measured using the 'pin-drop- technique’.
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Programming combinations used in the study
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Distribution of lead depth in PNfS:ONS vs PNLI
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Lead depth Correlates with Perception Threshold
• Pearson Correlation = 0.348, p≤0.001• n= 459 data points from 27 patients (head and low back subcutaneous) with 18
different stimulation configurations (27 points missing)
= data obtained from McRoberts et al.
Similar trends were observed between the two studies.
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Lead depth studies
Across three separate studies using three different depth measurement methods, low back subcutaneous paresthesia
was observed at an average lead depth of 9.2 - 10.5mm.
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Paresthesia Descriptions
Paresthesia descriptions were classified into 5 groups based on cutaneous fibre type
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Distribution of categorised sensations at maximum discomfort
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Distribution of categorised sensations at 70% usage range
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Distributions of sensations at maximum discomfort amplitude
• The LBP and ONS groups have similar distributions. Major sensations experienced are tingling, vibration, pinch, and stabbing.
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Low back PNfS has higher perception thresholds than ONS
Head (ONS) n = 8
Low Back n = 13
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Study summary
1. Implant depth of 10~12 mm from the surface can maximise the
target sensation (Aβ_FA) of PNfS effective pain relief.
2. Cathodal threshold is lower than anodal one (as in Spinal cord
Stimulation (SCS)).
However, it is likely that anodes reach threshold within the normal usage range of
current in PNfS.
3. In PNFS both cathodes and anodes may be used to target the
stimulation location.
=
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PNfS 200 cases study
IRB approved
Prospective observational study over 2 years +
203 patients with intractable pain
Key pain regions: Occipital / craniofacial
Thoracic
Abdominal / groin
Low back
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PNfS 200 cases
Outcomes: Average pain (11 - point NPRS / VAS scale)
Percentage pain relief (%)
Oswestry Disability Index (ODI)
Analgesic medication use
Changes to paid employment (if applicable)
Patient satisfaction with the treatment
Adverse events monitored
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Results: occipital - craniofacial
• n = 63• an average pain reduction of 4.9 ± 0.32, on an 11-point scale
was reported (***p≤0.0001, Wilcoxon Mann-Whitney U-test)
Pre PNfS Post PNfS0
2
4
6
8
10
7.4
2.7
Reduction in Pain(data shown as Average Pain ± SEM)
11 –
poi
nt P
ain
Scal
e ***
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Results: thoracic
• n = 17• an average pain reduction of 5.3 ± 0.56, on an 11-point scale
was reported (***p≤0.0001, Wilcoxon Mann-Whitney U-test)
Pre PNfS Post PNfS0
2
4
6
8
10
7.3
2.3
Reduction in Pain(data shown as Average Pain ± SEM)
11 –
poi
nt P
ain
Scal
e
***
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Results: abdominal / groin
• n = 15• an average pain reduction of 5.8 ± 0.52, on an 11-point scale
was reported (***p≤0.0001, Wilcoxon Mann-Whitney U-test)
Pre PNfS Post PNfS0
2
4
6
8
10
7.3
1.6
Reduction in Pain(data shown as Average Pain ± SEM)
11 –
poi
nt P
ain
Scal
e
***
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Results: low back
• n = 108• an average pain reduction of 4.1 ± 0.26, on an 11-point scale
was reported (***p≤0.0001, Wilcoxon Mann-Whitney U-test)
Pre PNfS Post PNfS0
2
4
6
8
10
7.2
3.4
Reduction in Pain(data shown as Average Pain ± SEM)
11 –
poi
nt P
ain
Scal
e
***
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Results: occipital / craniofacial
• 66% of patients reported good (>50%) to excellent (>75%) pain relief
Excellent (100-75%)
Good (75-50%) Fair (49-25%) Poor (<24%) No Change0
10
20
30
40
50
60
70
42%
23.8%12.7% 7.9% 1.6%
% Pain Relief Experienced by Patients with PNfS(n = 63)
Prop
ortio
n of
Pat
ient
s (%
)
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Results: thoracic
• 82% of patients reported good (>50%) to excellent (>75%) pain relief
Excellent (100-75%)
Good (75-50%) Fair (49-25%) Poor (<24%) No Change0
10
20
30
40
50
60
70
58.8%
23.5%11.8%
0%
5.9%
% Pain Relief Experienced by Patients with PNfS(n = 17)
Prop
ortio
n of
Pat
ient
s (%
)
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Results: abdominal / groin
• 87% of patients reported good (>50%) to excellent (>75%) pain relief
Excellent (100-75%)
Good (75-50%) Fair (49-25%) Poor (<24%) No Change0
10
20
30
40
50
60
70
66.7%
20% 13.3%0% 0%
% Pain Relief Experienced by Patients with PNfS(n = 15)
Prop
ortio
n of
Pat
ient
s (%
)
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Results: low back
• 68% of patients reported good (>50%) to excellent (>75%) pain relief
Excellent (100-75%)
Good (75-50%) Fair (49-25%) Poor (<24%) No Change0
10
20
30
40
50
60
70
35.2% 32.4%15.8% 5.5% 11.1%
% Pain Relief Experienced by Patients with PNfS(n = 108)
Prop
ortio
n of
Pat
ient
s (%
)
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Results: combined areas
• combined regions PNfS, n = 203• an average pain reduction of 4.3 ± 2.5, on an 11-point scale was
reported (**p≤0.00, Wilcoxon Mann-Whitney U-test)
Pre PNfS Post PNfS0
2
4
6
8
10
7.3
3.0
Reduction in Pain(data shown as Average Pain ± SEM)
11 –
poi
nt P
ain
Scal
e **
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Results: combined areas
• 73% of patients reported good (>50%) to excellent (>75%) pain relief
Excellent (100-75%)
Good (75-50%) Fair (49-25%) Poor (<24%) No Change0
10
20
30
40
50
60
70
42%31%
14% 5%8%
% Pain Relief Experienced by Patients with PNfS(combined regions, n = 203)
Prop
ortio
n of
Pat
ient
s (%
)
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Does the pain relief last post-implant?
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Sustained pain relief: combined areas
• Pain relief achieved shortly after implantation was sustained for greater than 12 months
≤ 12 months follow up ≥ 12 months follow up ≥ 24 months follow up0
2
4
6
8
10
Pre,7.3
Post, 2.9
Pain Relief post-implant
VAS
Pain
Sco
res
n = 203
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Sustained pain relief: combined areas
• Pain relief achieved shortly after implantation was sustained for greater than 12 months
≤ 12 months follow up ≥ 12 months follow up ≥ 24 months follow up0
2
4
6
8
10
Pre,7.3 Pre, 7.4
Post, 2.9 Post, 3.0
Pain Relief post-implant
VAS
Pain
Sco
res
n = 203 n = 203
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Sustained pain relief: combined areas
• Pain relief achieved shortly after implantation was sustained for greater than 12 months
≤ 12 months follow up ≥ 12 months follow up ≥ 24 months follow up0
2
4
6
8
10
Pre,7.3 Pre, 7.4 Pre, 7.3
Post, 2.9 Post, 3.0Post, 3.8
Pain Relief post-implant
VAS
Pain
Sco
res
n = 203 n = 203
n = 68
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Results: combined areas
Extreme Decrease
Moderate Decrease
Slight Decrease
Increase No Change Unsure0
10
20
30
40
50
40%
26%
8% 4%20%
2%
Changes to Analgesic Usefollowing neuromodulation (combined regions, n = 203)
Prop
ortio
n of
Pat
ient
s (%
)
• 74% of patients reduced their analgesic use• reduction in analgesics correlated with improved pain relief (next slide)
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Results: combined areasPain Relief correlates with Decreased Analgesic Use
Good
Fair
PoorPain
Rel
ief
N/A NoChange
Increased Slightdecrease
ModerateDecrease
ExtremeDecrease
Change in Analgesic Use
Excellent
Pearson’s Correlation, r = 0.704; p ≤ 0.0001
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Results: combined areas
• Pre PNfS = 34.4 13.5 vs ≥ 12 months Follow Up = 28.3 6.4 (n = 203) • Disability was reduced following PNFS; (*p ≤ 0.03, t-test )
*
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Results: combined areas
0
10
20
30
40
50
12%
40%
0%8%
16%24%
Changes to paid employment following PNFS for pa-tients below 60 years (≥ 12 months)
Prop
ortio
n of
Pat
ient
s (%
)
48%
• 48% of patients below the age of 60 years increased their capacity for paid employment.
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Complications and adverse eventsOUTCOMES
Complication No. of patients
Reposition / Re-implant / Replace Explant
2007 2008 2009 2010 2011 2007 2008 2009 2010 2011
Hardware erosion 10 1 3 1 1 1 1 1 1
Lead Infection 2 1 1
Leads too superficial 5 1 2 1 1
Hardware migration 5 1 1 2 1
IPG pain 2 1 1
Implant rejection 2 1 1
TOTAL COMPLICATIONS2007 2008 2009 2010 2011
3 6 5 7 5
26 patients total(12.8% of all cases)
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Patient satisfaction (≥ 12 months)
Completely Sat-isfied
Very Satisfied Satisfied Not Comletely Satisfied
Unsatisfied0
10
20
30
40
50
60
70
28%35%
22%
6% 8%
Prop
ortio
n of
Pat
ient
s, %
• Overall, 85% of patients were satisfied with their outcome
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Summary
Science behind PNfS
Underlying Issues of PNfS therapy
Clinical data for key pain areas
Combined clinical data for 203 PNfS patients
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Conclusions
PNFS therapy for intractable chronic pain
conditions:
Safe
Effective
PNFS has the potential to fundamentally change
the way we think about pain management
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Conclusions
Peripheral Nerve field Stimulation
MIRAGE OR REALITY ?