Chapter 62 Peripheral Nerve Stimulation Flashcards
KEY POINTS 1. Peripheral nerve stimulation systems can be trialed prior to permanent implantation with an ultrasoundguided placement. 2. The long-term safety of permanent implants of percutaneous electrodes is not yet known with certainty. 3. Although percutaneous ultrasound-guided PNS is similar to peripheral nerve catheter placement for perioperative nerve blockade, the larger size of the needle and potential areas of placement are quite different. These differences mandate a very strict an
PNS used for a wide variety of chronic pain disorders
limb mononeuropathies, complex regional pain
syndrome, cranial neuralgias, headache disorders, and
regional pain not amenable to SCS
Theories of pain pathophysiology of how neuromodulation affects
chronic pain
direct effects on peripheral pain fibers through excitation failure, selective release of
pain-modulating neurotransmitters, and changes in cerebral
flow in pain centers.
an important
consideration when attempting to stimulate a sensory fascicle
The complex fascicular arrangement of upper extremity nerves
peripheral nerve arrangements
will have one to several
internal fascicles that routinely change locations within the
nerve topography.
An open neurosurgical approach allows what testing
only motor testing with a nerve stimulator, unless
the operator performs a wake-up test.
Ultrasound allows
The key nerves of interest are usually superficial
enough to be seen well under US. US also allows visualization of surrounding key soft tissue structures and in each case, care should be taken to not pierce muscle compartments
or vascular structures along the needle/lead path to the nerve
For implantation cases, the lead can be anchored
to
the superficial muscle fascia with a strain relief
loop.
redundancy of the number of lead contacts in the vicinity of the desired fascicle is important because
The nerve will normally translate within the neurovascular
compartment as much as several millimeters. This
means that a normal nerve may move up to several millimeters
between the muscle and surrounding fascia with
flexion, extension, and rotation of the extremity
The radial nerve is very close to the lateral surface of the humerus at a point
10 to 14 cm proximal to the lateral epicondyle
RADIAL NERVE PNS technique
Ultrasound scanning usually begins at the
elbow and, with the probe in a transverse orientation to the arm, continues proximally until the desired approach
is identified. The needle can be advanced
from posterolateral to anteromedial to lie between nerve and humerus.
RADIAL NERVE PNS indications
Potential patients could include those with posterior interosseous neuropathies or
resistant lateral epicondylitis (tennis elbow) patients.
Solution of problems with lead migration
Subsequent radial nerve placements have utilized
more than one electrode, and a 4-week period of soft arm immobilization to allow the electrode(s) to better fibrose into place.
ULNAR NERVE location
The ulnar nerve is superficial to the medial head of the triceps muscle. the nerve was easily identified at a point 9 to 13 cm proximal
to the medial epicondyle in the medial/posterior
arm.
ULNAR NERVE PNS technique
Ultrasound scanning can commence at the elbow
and, with the probe in a transverse orientation to the arm, continue to scan more proximally until the nerve fascicular
arrangements can be well identified. The needle may be advanced from posterior to anterior on the medial aspect
of the arm to lie between nerve and humerus, staying superficial to the medial head of the triceps.
In ULNAR NERVE PNS Caution is important to avoid injury to the
medial cutaneous nerve of the arm, as well as
the recurrent ulnar collateral artery
MEDIAN NERVE location
The median nerve enters the antecubital fossa medial to the biceps muscle and its tendon, and next to the brachial artery. In the upper forearm at a point
approximately 4 to 6 cm distal to the antecubital crease, the nerve passes between the two heads of the pronator teres muscle, and then passes under the sublimis bridge of
the two heads of the flexor digitorum superficialis
in the forearm an important consideration in terms of expected stimulation patterns of the Median nerve
common neural fascicular communications between the median and ulnar nerves
Median nerve stimulation may be accomplished either
superior to the elbow, or inferior.
The common peroneal nerve may be identified at its branch point from
the sciatic nerve, a point 6 to 12 cm proximal to the popliteal crease
POPLITEAL AREA PNS Technique
Either transverse or longitudinal placement can be used, with transverse placement being more forgiving of movement, but a greater number of possible electrodes contacting
the nerves with longitudinal placement. The needle may be
advanced from posterolateral to anteromedial in a slightly
oblique plane, attempting to avoid passing through the biceps femoris.
POPLITEAL AREA PNS One must also scan thoroughly to see
the sural branches to
avoid injury
POSTERIOR TIBIAL location
Approximately 8 to 14 cm proximal to the
medial malleolus, the nerve is in close proximity to the tibialis
posterior muscle, the digitorum profundus, one or two large veins, and the flexor hallucis longus.
POPLITEAL AREA PNS technique
US scanning begins
at the ankle near the medial malleolus, with the probe in a transverse orientation to the leg, and then continued
proximally until the desired approach is identified. The needle may be advanced from anterior to posterior along the medial aspect of the ankle to lie just superficial (or deep)
to the nerve.
