Background
Lead placement within the sacral foramen in sacral neuromodulation patients is guided
by visual assessment of the contraction of the pelvic floor musculature (PFM) and/or
verbal assessment of the sensation and location of sensation upon stimulation. Generally,
lead placement is proceeded by needle probing. This study evaluates which location
inside a single sacral foramen would be most ideal for the release of the permanent
electrode lead, by measuring electromyographic (EMG) motor responses of the PFM upon
stimulation of a peripheral nerve evaluation (PNE) needle.
Materials and Methods
In eight patients, four standard PNE needles, and in one patient, two PNE needles,
were introduced into the same foramen, parallel to the midline and parallel to each
other. Position was verified by X-ray. Needles were stimulated (square pulsed waves,
210 μsec, 14 Hz) at increasing amplitudes (1-2-3-5-7-10 mA). PFM EMG was measured
using the Multiple Array Probe (MAPLe) placed intravaginally or intrarectally, with
24 derivations. For this study, the mean (normalized) EMG was taken of all electrodes
and different positions within the foramen were compared using the Wilcoxon signed
rank test.
Results
A total of 202 PFM EMG measurements were recorded upon stimulation. EMG motor responses
of the PFM for current stimulation = <2 mA showed statistically significant higher
mean (normalized) EMG values for needles positioned cranial, medial, and cranial-medial,
in comparison to needles positioned caudal, lateral, and caudal-lateral (p = 0.004; p = 0.021; p = 0.002).
Conclusions
Our data suggest stronger PFM contractions are elicit in cranial- and medial-placed
PNE needles upon stimulation with clinically relevant current amplitudes (≤ 2 mA).
Placement of the lead should aim for this spot in the foramen.
Keywords:
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COMMENTS
Article info
Publication history
Accepted:
March 6,
2019
Received in revised form:
February 1,
2019
Received:
January 1,
2019
Footnotes
For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http://www.wiley.com/WileyCDA/Section/id-301854.html
Source(s) of financial support: Medtronic provided funding for the study.
Identification
Copyright
© 2019 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.
