Prakash Rao

Report
Mapping of Posture-Dependent Shifts in
Paresthesia during Spinal Cord
Stimulation (SCS)
Cong Yu MD1, Thomas Yang MD1, Shaun Kondamuri MD2, Satish Dasari MD2,
Prakash Rao BS3, Kerry Bradley MS3, Lilly Chen MD3, Nitzan Mekel-Bobrov PhD3,
Jay Schnitzer MD PhD3
1Swedish
Medical Center, Seattle, WA
2Midwest Interventional Spine Specialists, Munster, IN
3Boston Scientific Neuromodulation, Valencia, CA
Disclosures
This study was funded by Boston Scientific
Neuromodulation.
Cong Yu MD serves as a consultant for Boston Scientific
Neuromodulation and St. Jude Neuromodulation.
Thomas Yang MD serves as a consultant for Boston
Scientific Neuromodulation.
Prakash Rao, Kerry Bradley, Lilly Chen, Nitzan MekelBobrov, & Jay Schnitzer are employees of Boston
Scientific Neuromodulation
Background: Importance of Pain-Paresthesia Concordance
“Superposition of stimulation paresthesias upon a patient’s
topography of pain was found to be a statistically significant
predicator of successful relief of pain.” (North et al., 1991)
(North et al., 1991)
Background: Paresthesia Distribution
• Dorsal CSF layer (dCSF) = distance between epidural
contacts and the top of the dorsal columns (DCs).
• Thickness of dCSF largely influences perception threshold
and paresthesia distribution.
North, 2006
Background: Posture Causes Changes in dCSF Space
“dCSF space not only varies from one level to the spine to
another, but also at a given level in a given patient” (Olin et al., 1998)
The dCSF space changes with posture
due to changes in spinal cord position
within the dural sac:
• Cord is more ventral when sitting, standing, or prone
• Cord is more dorsal when supine
(Olin et al., 1998)
Background: Previous Studies on Posture’s Effect on SCS
• 29 patients implanted with Octrode™
leads in cervical and thoracic spine
• 42 patients trialed with T8-T12 lead
placement
• Posture had significant effect on
charge/pulse.
• Measured voltage thresholds with 4contact perc leads (Pisces™ Quad)
•Significantly higher charge/pulse
required when patients in
sitting/standing position.
• Voltage requirements increased when pts
moved from supine to sitting/standing
positions.
Olin et al., 1998
Cameron et al., 1998
How does posture affect paresthesia distribution?
Study Design
Objective
Map shifts in paresthesia distribution associated with changes in posture
N
13 enrolled subjects
Number of Sites
2
Subject
Characteristics
Chronic neuropathic pain of the lower back and/or legs
Endpoint
Patient-reported paresthesia locations recorded at perception threshold
in seated and supine positions
Study Schedule
SCS permanent implant
2 weeks post-implant
4 weeks post-implant
12 weeks post-implant
26 weeks post-implant
52 weeks post-implant
Methods
SCS implant procedure
• Precision Plus™ SCS IPGs
• 2 Linear™ octapolar percutaneous leads positioned between T8-10
Programming
• Fixed 8mm ctr-ctr bipole, same lead and contacts used throughout
study
• Pulse width = 500 µs
• Frequency = 50 Hz
Confirmation of lead position by fluoroscopy
Data collection with patient in alternative postures
• seated
• supine
+
Results
• 12 subjects: at least 3 follow-up visits
• Mean follow-up time: 55±3 weeks
post-IPG implant procedure
• Subjects’ verbal descriptions of
paresthesia locations were mapped
onto an electronic body map
Results
Supine
Centroid Analysis:
Centroid was calculated by geometric
decomposition for each subject’s
paresthesia distribution in supine and
upright positions, to identify the mean of
all points in the shape of the paresthesia
across the body.
Rostral
Rostral Shift:
Changes in paresthesia distribution
between positions were then analyzed
as a paresthesia centroid shift with
directionality along the three axes.
Statistically significant supine-to-upright
rostral centroid shift (P<0.05).
Caudal
Results
Supine
Centroid Analysis:
Centroid was calculated by geometric
decomposition for each subject’s
paresthesia distribution in supine and
upright positions, to identify the mean of
all points in the shape of the paresthesia
across the body.
Rostral
Rostral Shift:
Changes in paresthesia distribution
between positions were then analyzed
as a paresthesia centroid shift with
directionality along the three axes.
Statistically significant supine-to-upright
rostral centroid shift (P<0.05).
Caudal
Results
Dermatomal Preference:
Supine
Paresthesia locations were remapped to
dermatome segmentation.
Relative frequency of each dermatome
was calculated and compared to expected
frequency under random distribution.
Statistically significant paresthesia
preference in the upright position was
found for the anterior dermatomes of
the lower extremities L1-L5 (P=0.03)
Upright
Discussion: dCSF’s Influence on DC/DR Recruitment
Sitting
Supine
Adapted from
Holsheimer, 1997
Change in
fiber type
selectivity
Conclusions
When the patient moves from a supine to upright position:
• Initial site of paresthesia changes
• Paresthesia shifts rostrally
• Paresthesia favors anterior dermatomes in the lower extremities
Selective activation of a particular fiber type or a discrete group of fibers
may disrupt paresthesia concordance.
These observations suggest that changing stimulation amplitude alone
does not adequately compensate for shifts in paresthesia distribution due to
posture.
Common clinical mitigation: creating a therapeutic program dedicated for
each position. Each program may have unique amplitude, pulse width,
frequency, or anode-cathode programming.

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