Management of Peripheral Nerve Entrapment (Carpal Tunnel Syndrome)

1. Dr. Shahnawaz Alam
MCh-Neurosurgery
Management of Peripheral
Nerve Entrapment
(Carpal Tunnel Syndrome)
Moderated by:
Dr. V. C. Jha
HOD, Dept. of Neurosurgery

2. • Entrapment neuropathies are widespread and debilitating clinical conditions that
have a profound physical, psychological, and economic impact.
• In general, surgical interventions for these entrapment neuropathies carry a very
favourable outlook, with relatively low risk for serious morbidity and high success
rates for relief of symptoms and recovery of useful neurological function.
• Following the lead of other surgical specialities, peripheral nerve surgeons in
recent years have applied minimally invasive techniques to nerve entrapment
surgery in the hope of reducing surgical morbidity and postoperative recovery
times.
INTRODUCTION

3. • An entrapment neuropathy is defined as pressure or pressure-induced injury to
a segment of a peripheral nerve secondary to anatomic or pathologic structures.
• Tension on a nerve associated with adhesion to an adjacent mobile or static
anatomic structure may also be causative.
• Some patients have a predilection for entrapment neuropathies related to
congenital narrowing of the nerve’s osseous tunnel or thickening of an
overlying retinaculum.
• Abnormalities intrinsic to nerves such as diabetic neuropathy and autoimmune
neuritis may also cause nerve swelling or decreased tolerance to mild
compression.
• Inflammation or edema of adjacent structures, such as tendons, may reduce the
size of the passageway for the nerve, and mechanical forces on the nerve can
result in nerve compression.

4. • Damage to the myelin sheath and axonal disruption are end stages of chronic
compression that result in irreversible nerve damage.
• Not all nerve fibers are equally susceptible to pressure; larger fibers are more
susceptible than small fibers, and fascicular location within the nerve may also
affect vulnerability, depending on the force vectors applied.

5. MEDIAN NERVE
• Carpal tunnel decompression is the most common operation for peripheral
nerves, with more than 350,000 procedures performed annually.
• The prevalence of electrophysiologically confirmed, symptomatic carpal tunnel
syndrome (CTS) is approximately 3% in women and 2% in men, with a peak
prevalence in women older than 55 years.
• The earliest description of CTS was by Sir James Paget in 1854; The underlying
pathologic process of CTS is thought to be increased pressure within the carpal
tunnel.

6. • When the pressure within the tunnel exceeds perfusion pressure into the
nerve, adequate circulation and nutrition to the nerve fibers are
compromised.
• At 30 mm Hg, axonal transport is impaired, and between 30 and 40 mm Hg,
paresthesias and neurophysiologic changes are seen.
• Axonal block can be seen at 50 mm Hg, and at 60 mm Hg, complete
intraneural ischemia occurs, with resultant sensory and motor block.
• The median nerve is thought to respond to these effects over time with
endoneurial edema, demyelination, distal axonal degeneration, and fibrosis,
with intervening periods of regrowth of axons and remyelination.

7. Anatomy
• The carpal tunnel is a fibro-osseous
passageway in the anterior aspect of
the wrist that is formed by the carpal
bones and flexor retinaculum, also
known as the transverse carpal
ligament (TCL).
• The floor of the carpal tunnel is
composed of the volar radiocarpal
ligament and other bridging ligaments
inter-connecting the pisiform and hook
of the hamate medially and the
tubercles of the scaphoid and trapezium
laterally.
• The TCL forms the roof by attaching
medially to the pisiform and hook of the
hamate and laterally to the scaphoid
tuberosity and crest of the trapezium.
Surgical anatomy of the carpal tunnel
A, Flexor retinaculum. B, Median nerve.
C, Palmar cutaneous branch.D, Recurrent motor
motor branch.

8. • The carpal tunnel is approximately 4 to 6 cm in length and contains the
median nerve and its vascular bundle, four tendons each of the flexor
digitorum superficialis (FDS) and profundus (FDP) muscles, and the tendon of
the flexor pollicis longus muscle.
• The TCL is approximately 3 to 4 cm in width and 2.5 to 3.5 mm in thickness.
The ulnar nerve (UN) and ulnar artery run superficially on the ulnar side of
the TCL, and the tendon of the flexor carpi radialis is enveloped by two layers
of the TCL on the radial side of the wrist.

9. • The median nerve provide motor innervation to the lateral two lumbricals and
sensory innervation to the palmar surfaces and the distal dorsal portions of the
thumb, index finger, middle finger, and lateral half of the ring finger.
• The median nerve is vulnerable to compression at two particular sites in the
carpal tunnel. The first site is the proximal edge of the TCL, and the second is
adjacent to the hook of the hamate.

10. Common Conditions Associated
with Carpal Tunnel Syndrome
Possible Entrapment Sites of the
Median Nerve

11. Clinical Findings
• Patients with CTS most often complain of pain and paresthesias in the median
nerve distribution in the hand, particularly after strenuous wrist movements or
at nighttime.
• The pain is often described as burning and may radiate proximally.
• Frequently, the patient will describe the improvement of symptoms by shaking
the affected hand, which may support the venous stasis theory.
• Important questions for the patient include the duration, quality, and severity
of symptoms, as well as aggravating and relieving activities.
• Certain conditions should be considered during the patient interview pregnancy
(particularly the third trimester), renal failure and dialysis, rheumatoid arthritis,
hypothyroidism, acromegaly, and amyloidosis.

12. • A thorough past medical and surgical history must be taken, including
medical comorbid conditions and a history of trauma or fractures of the
upper extremity.
• The social history should include questions about repetitive wrist motion
with work or hobbies.
• Certain sports are associated with the development of CTS. Wheelchair
athletes, archers, bicyclers, bodybuilders, football players, golfers, and
wrestlers are prone to CTS.
• Screening questions for alcoholism should also be asked. The patient’s family
history should be obtained as well.

13. • On examination, the entire shoulder and limb should be inspected for atrophy
or asymmetry.
• Thenar atrophy is important to identify because it is a clue to the severity of
CTS.
• Coexistent hypothenar or first dorsal interosseous muscle atrophy may signify
compression at the thoracic outlet or ulnar entrapment neuropathy.
• Palpation is performed over the entire length of the median nerve from the
brachial plexus to the hand to check for masses, points of tenderness, and
adjacent bony abnormalities.
• Motor examination should include all median-innervated muscles.

14. • Certain provocative manoeuvres can be used when examining a patient with
suspected CTS. A positive finding occurs when the maneuver or position elicits
symptoms in the distribution of the median nerve in the hand.
• Tinel’s sign is elicited by tapping over the carpal tunnel; sensitivity for Tinel’s sign
in patients with CTS ranges from 45% to 75%, and its specificity ranges from 40%
to 67%.
• The Phalen test is performed by having the patient flex the wrist as far as possible
and holding that position for 60 seconds, and the sensitivity and specificity of this
test range from 4% to 86% and 48% to 54%, respectively.
• The pressure provocation test (Durkan compression test) is performed by the
examiner placing a thumb over the carpal tunnel and exerting downward pressure
for 30 seconds. This test has a significantly better sensitivity and specificity of 82%
to 89% and 90% to 99%, respectively.

15. Diagnostic Evaluation
• Electrophysiologic testing can provide important objective information to
support the diagnosis of CTS.
• Palmar sensory latency, measured by stimulating sensory fibers in the palm and
recording over the wrist, is the most sensitive test for CTS.
• Distal motor latency is usually prolonged but may be normal in 25% of patients
with other signs and symptoms of CTS.
• Sensory nerve action potentials (SNAPs) are either unrecordable or of low
amplitude at the wrist.
• Electromyographic recording of the abductor pollicis brevis or opponens pollicis
may reveal spontaneous fibrillation potentials and positive sharp waves, as well
as an increased incidence of long-duration, polyphasic motor unit potentials.
• These electrophysiologic data are compared with recordings from the ipsilateral
ulnar and radial nerves because the contralateral median nerve may be affected
by subclinical CTS.

16. • Electrodiagnostic studies are also helpful in grading the severity of CTS.
• In mild CTS, the SNAP or mixed nerve action potential (NAP) is often
prolonged, and SNAP amplitude may be below the lower limit of normal.
• In moderate CTS, there are findings of mild CTS plus prolongation of median
motor distal latency.
• In severe CTS, median motor and sensory distal latencies are prolonged, with
absent SNAPs or mixed NAPs or absent or reduced thenar compound motor
action potentials, or both.
• Fibrillations, reduced recruitment, and changes in motor unit potential are
often seen in severe cases.

17. • Imaging can be a useful adjunct in the diagnosis of CTS. Plain films of the wrist
can identify bony abnormalities such as fractures.
• Refinement of ultrasound techniques has allowed direct visualization of neural
structures and associated sites of constriction, compression, or both.
• An entrapped peripheral nerve may appear hypoechoic, swollen, or flattened
or exhibit any combination of these features.
• Ultrasonography has been shown to be highly sensitive and specific in patients
with clinical and electrophysiologic signs of CTS, as well as in patients with
clinical signs of CTS but negative electrodiagnostic studies.
• A cross-sectional area of the median nerve of 10 mm2 or larger at the level of
the pisiform bone is the most commonly used parameter to diagnose CTS on
ultrasonography.

18. • Improvements in MRI have resulted in greater sensitivity in the detection of
peripheral nerve inflammation.
• Increased signal intensity within inflamed peripheral nerves may be seen on
short tau inversion recovery (STIR) images or fat-suppressed T2-weighted spin
echo images.
• Nerve thickening or nerve enlargement on MRI can also signify inflammation.
Magnetic resonance neurography, a technique based on enhancing signal
differences between nerves and surrounding tissues, has increasingly been used
for the diagnosis of entrapment neuropathies.
• These MRI techniques may be useful in the diagnosis of CTS in patients with
normal electrophysiologic studies or in those with an underlying systemic
neuropathy altering the electrophysiologic results.

19. Conservative Treatment
• CTS is usually a progressive condition, but a course of conservative therapy
should be completed before surgical intervention.
• Wrist splints, physical therapy, lifestyle modification, ultrasound therapy, diuretics,
nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids (either oral or
direct carpal tunnel injection) are several conservative options available, but
efficacy has yet to be proved for many of these approaches.
• Splinting of the affected wrist is the most commonly used nonoperative
treatment and is supported by both anatomic and clinical studies.
• Anatomically, a wrist splint places the wrist in the neutral position, which has
been shown to create the least amount of pressure or friction, or both, within the
carpal tunnel.

20.  Piazzini et al. recently performed an extensive review of the literature regarding
the efficacy of conservative treatment of CTS.
 Their findings were the following: (1) locally injected steroids produce a
significant, but temporary improvement; (2) wrist splints are effective,
particularly if used full-time; (3) steroids are more effective than NSAIDs or
diuretics; (4) ultrasound therapy may be effective, and laser therapy shows
variable results; and (5) exercise therapy and pyridoxine (vitamin B6) are
both ineffective.
 Randomized controlled studies have also shown that surgical decompression of
the carpal tunnel is superior to both wrist splinting and steroids in terms of
relief of symptoms and neurophysiologic outcomes. In regard to CTS in the
setting of pregnancy, symptoms often resolve on delivery.

21. Surgical Techniques
• Open Technique: The goal of the open approach is complete division of the
TCL and decompression of the median nerve, with preservation of the
palmar cutaneous and recurrent motor branches of the median nerve.
• This procedure is typically performed on OPD basis with LA and, in some
cases, mild sedation administered by an anesthesiologist. Other anesthetic
options are general anesthesia, regional block, or a Bier block.
• The patient is positioned supine with the arm abducted and forearm
supinated on a hand table or arm board.
• After careful skin preparation and draping, the wrist is often placed on a roll
to provide wrist extension. Loupe magnification and headlights are useful
adjuncts.

22. • A 3-4 cm (1.5-3 cm in a mini-
open approach) straight or
slightly curvilinear incision is
marked starting at the distal
wrist crease and ending at a
point intercepting an imaginary
line (Kaplan’s line) drawn from
the distal border of the
extended thumb to the pisiform
prominence, in line with the
long axis of the radial side of
the ring finger.

23. • The incision is placed ulnar to or in line with the tendon of the palmaris
longus and the major thenar skin crease. The incision may have to be
extended distally for better exposure in large hands.
• After infiltration of the proposed incision with local anesthetic, an incision is
made with a No. 15 scalpel.
• Deep to the skin, subcutaneous fat and the palmar fascia are encountered,
with care taken to protect the palmar cutaneous branch of the median
nerve, which is not consistently visualized.

24. • A small self-retaining retractor such as an Alm retractor or a small bur-hole
retractor is placed, and meticulous hemostasis is maintained with bipolar
electrocautery.
• The TCL is encountered deep to the palmar fascia; occasionally, the thenar and
hypothenar muscles may obscure the ligament.
• The TCL is divided at its midpoint in layers with either a No. 15 scalpel or small
scissors, and a fine instrument such as a Jacobson, McCabe, or a flat dissector is
used to elevate each layer.
• The recurrent motor branch of the median nerve may be trans-ligamentous or
subligamentous and must be carefully avoided and protected. When the median
nerve is visualized, the TCL is incised both proximally and distally.

25. Mini-open carpal tunnel release
A. Planned incision measuring 2 cm starting at the distal wrist crease and extending distally in
line with the third interspace.
B. Intraoperative identification of the median palmar cutaneous nerve (identified with a No. 4
Penfield dissector).
C. After division of the transverse carpal ligament (arrows), the median nerve (MN) is visualized.
A Senn retractor is placed at the distal aspect of the incision to improve visualization.

26. • Proximally, the skin is elevated to permit visualization 2 to 3 cm into the
forearm. The proximal TCL and a distal portion of the antebrachial fascia are
incised.
• The distal TCL is incised until the deep palmar fat pad is visualized, taking care
to avoid any sensory or ulnar motor branches that may be encountered just
distal to the ligament.
• The proximal and distal portions of the incisions are probed with either the
surgeon’s fifth finger or a Penfield No. 4 dissector.
• At this point the carpal tunnel may be explored for tumor, ganglion cysts,
muscle anomalies, or any other structural abnormality.

27. • Before closure, the wound is inspected for hemostasis, and any bleeding
points are coagulated with bipolar electrocautery; if used, the tourniquet
should be released at this point.
• The wound is irrigated and then reapproximated with several absorbable
subcutaneous sutures. The skin is closed with either absorbable or
nonabsorbable monofilament in either a running or mattress configuration.
• A bulky hand dressing is then applied, and the patient is encouraged to
perform gentle range-of-movement exercises as soon as possible.
• Postoperative splinting is not usually recommended because splinting has
not been shown to improve wound healing, reduce postoperative pain, or
diminish scar tenderness.

28. • Results from the open carpal tunnel release are generally excellent.
 From the Louisiana State University Health Sciences Center (LSUHSC) series of
376 carpal tunnel releases, 89% of the patients were satisfied with their results.
 Improvement in pain was seen in 87% of patients, improvement in
paresthesias in 92%, improvement in numbness in 56%, and improvement
in weak- ness in 42% of patients.
 Major symptoms persisted in 6% of patients, and complications included
wound infections, reflex sympathetic dystrophy, and hematoma.

29.  Endoscopic Techniques: Endoscopic carpal tunnel release (ECTR) has been
performed since the late 1980s, and several different endoscopic techniques
involving either a uniportal or biportal approach have been developed since.
• For both types of approaches, a tourniquet and either local anesthesia or a
Bier block is used.
• A small incision is made at or just proximal to the distal wrist crease on the
ulnar side of the palmaris longus tendon.
• The antebrachial fascia is exposed and divided bluntly. An elevator is placed
deep to the antebrachial fascia and superficial to the flexor tendons.
• An obturator and slotted cannula are then inserted into the carpal tunnel while
staying superficial to the median nerve and flexor tendons.

30. • In the two-portal technique, the obturator and cannula are brought through
the skin approximately 4 cm distal to the distal wrist crease, the obturator is
removed, and an endoscope is placed through the distal opening.
• The cannula is slotted to allow passage of a blade. The TCL is divided in
either a proximal-to- distal or a distal-to-proximal manner.
• In the uniportal technique, the endoscope camera follows the blade. With
these endoscopic techniques, no attempt is usually made to visualize the
median nerve.

31. • After the TCL has been completely divided, the cannula is removed, the
tourniquet is deflated, and when hemostasis is obtained, the skin incision or
incisions are closed with simple skin stitches.
• Potential advantages include a shorter recovery time, less postoperative pain,
and reduced wound complications.
• Drawbacks include a steep learning curve; less visibility, which may result in
incomplete sectioning of the TCL and increased nerve injury risk to both
median recurrent and distal ulnar elements; and increased cost associated with
endoscopic instruments.

32.  Hankins et al. reported a large case series of patients who underwent
ECTR with the Brown biportal technique.
 Of the 14,722 patients included in this series, 82.6% had complete
resolution of symptoms, 14.7% had some resolution, and 2.6% had
no improvement and required open revision.
 Although ECTR has a growing number of proponents, open carpal
tunnel release (OCTR) is still the approach used by most peripheral
nerve surgeons.

33. References:
• Youmans and Winn neurological surgery 7th edition
• Ramamurthi & Tandon's textbook of neurosurgery 3rd edition
• Internet
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