· Most common entrapment neuropathy.
· F>M, usually 30-60 years.
· Often bilateral, but worse in the dominant hand.
· Manual work.
· Flexor tenosynovitis.
· Pregnancy.
· Medical – hypothyroidism, acromegaly, rheumatoid arthritis, amyloidosis.
· Pain – usually the most prominent symptom.
· Aching and burning pain in fingers, hand, wrist, forearm, sometimes upper arm.
· Worst at night and in the morning.
· Relieved by shaking or exercising the hand.
· Sensory – tingling and pins and needles.
· May not be localised to the median nerve distribution by the patient.
· May or may not be altered sensation in the median nerve distribution.
· Tinel’s sign – percussion over the median nerve at the wrist provokes sensory symptoms.
· Phalen’s sign – sustained wrist flexion (30 seconds) provokes sensory symptoms.
· Wasting and weakness – most do not have these, though there may be abductor pollicis brevis wasting.
· Clinical.
·
Nerve conduction studies
can be used.
- electrodes taped to skin; forearm and hand x3
- stimulus delivery; analysis to determine if impulses are slowed
within the carpal tunnel - localizes site of pathology
- evalutes for neuropathy with conduction delay; demyleinating
condition (as opposed to other neuropathy; ie axon loss).
- hence can help in both localization and specificity of
neuropathy; confirming diagnosis of carpal tunnel
- excludes other differentials; e.g. polyneuropathy, nerve root or
plexus problems, motor neuron disease, myopathies
- note that in early phase of the disease, can be normal.
· Change occupation.
· Diuretics.
·
Surgical decompression.
Capral
Tunnel
What is Carpel tunnel
syndrome
• Symptoms and signs related to compression of
the median nerve in the carpel tunnel
What are the causes
• Idiopathic –
often associated with
pregnancy. Female:Male 8:1. 40-50’s.
• Distal radius
fracture
• Disease which increase volume of tissue in
carpel tunnel: Rheumatois synovitis,
hypothyroidism, Acromegaly,
amyloidosis, Gout, Lipoma, ganglion, neuroma.
• Renal failure with AV
fistula
• Daibetes increases
sensitivity of nerve to damage
• Other: Myeloma,
haemophilia, occupational
How is the diagnosis
made
• History.
• Phalen’s test: numberness over the median nerve
distribution when the hands are
pushing back
• Tinnel’s test
• Nerve conduction studies
How
do evaluate nerve conduction study?
Motor NCS
Motor
NCS are performed by
electrical stimulation of a
peripheral nerve and recording from a muscle supplied by this nerve. The time it
takes for the
electrical impulse to travel from the stimulation to the
recording site is
measured. This value is called the latency
and
is measured in milliseconds (ms). The size of the response -
called the
amplitude - is also measured. Motor amplitudes are measured in
millivolts (mV).
By stimulating in two or more different locations along the same
nerve, the NCV
across different segments can be determined. Calculations are
performed using
the distance between the different stimulating electrodes
and the difference in latencies.
Sensory NCS
Sensory
NCS are performed by
electrical stimulation of a
peripheral nerve and recording from a purely-sensory portion of
the nerve, such
as on a finger. The recording electrode is the more proximal of
the two. Like
the motor studies, sensory latencies are on the scale of
milliseconds. Sensory
amplitudes are much smaller than the motor amplitudes, usually
in the microvolt
(μV) range. The sensory NCV is calculated based upon the latency
and the
distance between the stimulating and recording electrodes.
What are the
non-surgical treatments
• Night splint,
steroids injections,
diuretics (non value)
What are the attachments
of the flexor retinaculum
• Radial: Tubercle of scaphoid and ridge
of trapezium – splits on the
radial side to enclose the tendon of FCR.
• Ulna: Pisiform and hook of hamate
What structures pass
superficial to carpel tunnel
• Superficial branch of ulna nerve, ulna
artery, palmaris longus
tendon and palmar cutaenous branch of median nerve.
What are the contents of
the carpel tunnel
• Flexor pollicis longus
tendon – the radial bursa
envelopes these tendons
• FDS tendons (in two
rows)
• FDP tendons in a single
row – a common synovial
sheath enclosed the long flexors of the fingers which is open in
the radial
side (ulna bursa) to allow blood vessels to the tendons to enter
• Median nerve –lie
between the FPL and FDS to middle
finger
• FCR lies in its own
compartment and is not part
of the carpel tunnel
What is the arrangement
of the tendons of FDS
Those
to the ring
and middle fingers form a superficial row with the tendons to
the index and
little finger in a deep row
What are the variations
of the recurrent motor branch
of the median nerve
• 50% - given off the radial side of the
median nerve distal to the
flexor retinaculum and is recurrent
• 33% - given off the radial side of the
median nerve in the carpel
tunnel and passes through the tunnel and then takes a recurrent
course to innervate
the thenar muscles
• 20% - arises from the radial side of the
median nerve and passes
through the flexor retinaculum
(non-recurrent)
• Rare variants:
—
Arising from ulna side of
median nerve and
takes a recurrent course across the superficial aspect of the
flexor
retinaculum
—
High division of median
nerve so two branches
lie in the carpel tunnel
How do you differentiate
the nerve from the tendons
The
nerve is white
with a fine vaso nervorum on its surface. The tendon bulge in
their synovial
sheaths
How do you perform
carpel tunnel release
• In an appropriately consented, prepared
patient
• I use nerve conduction studies to confirm
diagnosis.
• I check the nerve conduction studies with
the patient and mark the
side for surgery in anesthetic bay
• GA without local anesthetic.
• Elevate and exsanguinate
arm. Apply high arm tourniquet. Inflate to 200mmHg. Note
tourniquet time.
• Sterile prep and drape with arm on arm
table using a hand board or
lead hand to control fingers
• Mark incision with pen: line
of ulna side of ring finger. From distal dominant crease
of wrist to transverse line drawn from base of outstretched
thumb
• Incise through skin. Use skin hooks to
place palmar aponeurosis on
tension and incise through using scapel. Care not to damage
superficial palmar
arch at distal limit of wound
• Place small self retaining retractor. Make
a nick in the flexor
retinaculum with scalpel to the ulna side of midline.
• I place a Macdonald
dissector under the flexor retinaculum
to clear any adhesions
• With the Macdonald dissector separating
any underlying structures I
incise the flexor retinaculum under direct vision from the
distal limit using
the scalpel whilst keeping the median nerve in direct vision.
• I identify and protect the motor branch of
the median nerve.
• I inspect the tunnel for other
space-occupying lesions – Lipoma or
ganglion
• I lift the skin of the wound proximally
using the skin hooks to ensure
that there is no remaining restriction of the nerve. If any
fibers remain these
are divided under vision (without extending the skin incision)
protecting the
median nerve with the Macdonald dissector using iris scissors.
• It is my practice to deflate the
tourniquet and achieve secure
haemostatsis with biplaor diathermy.
• I observe pulsitile vascular flow to the
median nerve
• Once haemostasis is complete, I close the
skin using interrupted 4/0
Nylon to skin only.
• I apply a Telfor dressing, velban and
crepe so that the wrist is held
in a position of dorsiflexion to prevent bow stringing of the
tendons
What
are the complications
• Damage to the motor branch of median nerve
– if this occurs repair
immediately using an operating microscope
• Damage to superficial palmar branch of
median nerve causing anesthesia
and painful neuroma
What
is the pathogenesis of
nerve compression syndromes
Direct compression against
the nerve is associated
with ischaemia
• Initial temporary ischaemia with certain positions
produces parasthesia
• With consistent
chronic compression,
demyelination occurs with persistent symptoms of pain
and weakness
• As compression progresses Wallerian
degeneration occurs and
the nerve segment
ceases to function
What
other processes lead to
nerve damage
• Transection – unless the nerve
epineureum is
re-approximated nerve re-growth cannot occur
• Nerve infarct due
to vasculitis or
atherosclerotic disease
• Infalmmatory
disorder – monomyelic
amyotrophy – a focal motor neuron cell loss
• Metabolic
disorders – Diabetes,
hypohyroidism
What
is the significance of
asymptomatic nerve conduction defects
• If slowing occurs
across a certain segment
without symptoms, a clinical syndrome is not considered to
exist until symptoms
develop.
How
do you interpret nerve conduction
studies
• Focal entrapments of radial, median or
ulna nerves show evidence of
conduction slowing and block across the affected segments.
• Electromyography confirms the diagnosis
and provides insight into
lesion severity
• In
plexopathy, abnormalities are found in
several nerves emanating from one region of brachial plexus
(eg upper trunk).
EMG may show fibrillation potentials and positive sharp waves
and chronic
reinnervation in muscles innervated by the upper trunk
• In
radiculopathy sensory and motor studies are
usually normal.
Abnormalities are identified on needle examination and affect
the muscles
derived from involved roots.
What
about imaging
• MRI of cervical spine may complement EMG
findings or provide
additional information
What
are the other nerve
compression syndromes
• Commonly ulna and median nerve entrapments
•
Ulna neuropathy at elbow may
be due to
•
Compression
in the epicondylar groove due to repeated subluxation
of the nerve with
elbow flexion over the medial epicondyle.
•
Cubital
tunnel syndrome: Compression of the nerve between the
two heads of
flexor carpi ulnaris with repeated elbow flexion.
•
Compression of the ulna
nerve at the elbow is the second most common nerve compression.
Can be
diagnosed with nerve conduction studies showing conduction
velocity slowing and
high resolution US showing nerve thickening
•
Commonly treated with
nocturnal splinting at 60 degrees and injection of steroids
•
Surgical options are to
split the aponeurosis between the two heads of flexor carpi
ulnaris and
transpose the nerve from the medial epicondylar groove into the
forearm
Compression
of ulna nerve at
the wrist
•
Compression
in Guyon’s canal – Compression in the space between the
pisiform and the
hamate through which the ulna nerve passes into the hand. May be
occupational
(due to hand posture during work) due to reduced volume in canal
due to ganglion
cyst, trauma, arthritis or compression against a bicycle handle.
•
Diagnosis confirmed by nerve
conduction and EMG
•
Non-surgical treatment
includes a wrist brace, occupational therapy to reduce pressure
on nerve at
wrok, NSAIDS
•
Surgical decompression of
Guyon’s canal
Pronator
syndrome
• Entrapment of
median nerve in proximal forearm
where it passes through pronator teres muscle
• Caused by hypertrophy of muscle in active
people (eg professional
bicycle riders).
• Produces forearm pain and loss of
sensation over thenar eminence
• Treatment is to reduce activity producing
symptoms, NSAIDS, injection
of methylprednisolone and lignocaine.
Surgical decompression is used if the disability persists
Meralgia
parasthetica
• Entrapment or
compression of the lateral
Cutaneous nerve of the thigh as
it passes between the ilium and inguinal ligament.
• The syndrome consists of pain and anesthesia
in the distribution of the nerve in the anterolateral thigh.
• Nerve
conduction studies are
unhelpful generally
• Common causes include obesity, tight
garments and scar tissue.
• Pregnancy and diabetes may be contributory
factors
• Inject LA with or without US-guidance to
confirm diagnosis (pain goes
away)
• Conservative treatment by advice to wear
less tight clothes, loose
weight is used first
• Local steroid injections
• Anticonvulsants
• Surgical decompression (sectioning the
inferior slip of the attachment
of the inguinal ligament to ASIS) or sectioning the LFCN as it
exits the pelvis
• An incision is made 1cm medial to ASIS
extending 4cm into thigh
• The deep fascia is incised (as the nerve
lies deep to deep fascia of
thigh).
• The nerve is found at the anterior border
of sartoius and followed
proximally to entrapment site beneath inguinal ligament
• All constricting bands are divided so that
the nerve lies quite free.
• For recurrent disease, the nerve is pulled
down and divided close to
the inguinal ligament so that the divided end lies above the
inguinal ligament.