Median
Nerve – Carpal Tunnel Syndrome.
Peroneal
nerve at fibular neck
Lateral
femoral cutaneous neuropathy
Interdigital
Neuropathy (Morton’s Neuroma)
Upper Limb
Anatomy
•
C6-T1
•
All
three trunks
•
Anterior
division
•
Lateral
cord (C6-C7) and Medial Cord (C8-T1)
•
Runs
through upper arm medial to the humerus
•
Anterior
to the medial epicondyle and just medial to the brachial artery
•
In
a minority of individuals there is a supracondylar process which eminates from the distal humerus
and is connected with a ligament (of Struthers) to the medial epicondyle – the median
nerve runs through this.
•
In
forearm runs beneath the lacertus fibrosus
(a thick fibrous band running from medial epicondyle to biceps tendon
•
Runs
between two head of pronator teres
•
Anterior
interosseous nerve is then given off posteriorly, 5-8cm distal to medial
epicondyle.
•
Passes
deep to FDS
•
Just
proximal to wrist palmar cutaneous sensory branch arises, runs subcutaneously
(to supply thenar eminence sensation)
•
Enters
wrist through carpal tunnel
•
In
the palm the nerve divides into motor (recurrent thenar motor branch) and
sensory branch.
Main median nerve
•
Pronator
teres
•
FCR
•
FDS
•
Palmaris
longus
Anterior interosseous nerve (pure motor)
•
FDP
•
Flexor
pollicis longus (FPL)
•
Pronator
quadratus
Recurrent thenar nerve
•
Lateral
lumbricals
•
Opponens pollicis
•
Abductor
pollicis brevis (APB)
•
Flexor pollicis
brevis (superficial head)
Proximal median neuropathy
Median Nerve – Carpal Tunnel Syndrome
Aetiology
and risk factors
•
Most
cases are idiopathic due to repeated stress on connective tissue in CT
•
Consider
other conditions if the non-dominant hand is the worst affected
•
Associated
conditions
o
Hypothyroidism
o
Rheumatoid
arthritis
o
Diabetes
o
Sarcoid
o
Amyloidosis
o
Mass
lesions on rare occasions (cysts, schwannomas)
o
Pregnancy
Clinical
•
Usually
bilateral – however usually worse in dominant hand
•
Sensory
– Paraesthesias and/or numbness
o
Medial
thumb to middle of ring finger, dorsal fingertips
o
Sparing
of thenar eminence (palmar cutaneous branch of median nerve which divides
proximal to carpal tunnel)
•
Motor
o
Thenar
wasting
o
Weakness
of thumb abduction and opposition
•
Symptoms
worse during sleep
•
Worsened
by wrist flexion and extension activities
•
Provocative
tests
o
Tinel’s sign – paresthesia
in fingers with tapping over CT
o
Phalen’s
maneuver – holding wrists flexed for 1-2 minutes produces
paresthesia
o
Reverse
Phalen’s – holding wrists in extension
o
Durkan’s carpal compression test – applying prolonged
pressure over the carpal tunnel to elicit symptoms – can be done with thumb or
with standardised pressure implement.
o
Hand
elevation test – hands held above head for 2 min – positive if reproduces
symptoms (Ahn 2001)
•
Flick
sign
o
Ask
the patient what the do when the experience symptoms
– positive if they demonstrate shaking out movement or flicking the wrists
o
Possibility
has high sensitivity and specificity
DDx
•
Central
lesion
•
C6-C7
radiculopathy
•
Brachial
plexopathy
•
Proximal
medial neuropathy (rare)
•
Peripheral
neuropathy
Electrophysiology
Aims:
1. Demonstrate focal slowing or
conduction block of median nerve across the carpal tunnel
2. Exclude median neuropathy in the region
of the elbow
3. Exclude brachial plexopathy
4. Exclude cervical radiculopathy
(C6/C7)
5. Look for polyneuropathy and
determine if median slowing is out of proportion
NCS
•
Median
motor studies:
o
May
be reduced CMAP amplitude due to conduction block or axonal loss
•
F
waves
o
Should
be prolonged to some extent as they travel through CT
o
F-M
eliminates CT segment – however still often prolonged due to retrograde loss of
largest conducting fibres
•
Digital
sensories
•
Mixed
nerve/Palm to wrist studies
•
Other
tests
o
Digit
4 sensory comparison
o
Median
2nd lumbricals vs Ulnar interossei
o
Digit
1 median vs radial comparison
-
Useful
if co-existant ulnar neuropathy prevents comparison
o
Segmental
sensory study across the wrist
-
Median
wrist to digit 3 velocity (=C)
-
Median
palm to digit 3 velocity (=B)
-
Across
wrist velocity A= (BxC)/((2xB)-C)
|
|
Stimulation |
Record |
Distance |
Significant result |
|
Palm-wrist |
Median palm Ulnar palm |
Median wrist Ulnar wrist |
80mm 80mm |
>0.2 [>0.4] |
|
Digit 4 sensory |
Median wrist Ulnar wrist |
Digit 4 Digit 4 |
110mm 110mm |
[>0.5] |
|
Lumbrical-interossei |
Median wrist Ulnar wrist |
Palm b/n 2nd and 3rd MC (ref on dig 2) |
100mm 100mm |
[>0.5] |
|
Radial comparison |
Median wrist Lat. radius |
Digit 1 Digit 1 |
100mm 100mm |
[>0.5] |
|
Segmental sensory study |
Median wrist Median palm |
Digit 3 Digit 3 |
130mm 65mm |
CV difference >10ms* |
* Need to calculate conduction velocity using
formula A= (BxC)/((2xB)-C) where C = wrist to digit 3
velocity and B = palm to digit 3 velocity.
EMG
|
|
|
Rationale |
|
ABP (C8-T1) |
|
Excludes C8-T1 radiculopathy, Lower trunk, severe proximal medial lesion |
|
Two C6-C7 muscles |
Pronator teres FCR Triceps |
Excludes C6-C7 radiculopathy causing sensory symptoms |
|
If APB abnormal: |
|
|
|
One proximal median muscle |
FCR, Pronator teres FPL |
Excludes proximal median lesion |
|
Two other non-median lower trunk/C8-T1 muscles |
FDI, EIP |
Exclude C8-T1, lower trunk lesion, polyneuropathy |
|
|
|
|
•
Test
o
ABP
o
2
C6-C7 innervated muscles
o
Proximal
median innervated muscles
o
2
Non-median lower trunk muscles to exclude
•
Look
for signs of denervation of APB
•
Can
miss 25% of cases
•
If
history is atypical MRI may help look for mass lesion etc.
Grading Severity
•
There
are a number of different scales.
•
These
have been well correlated with symptoms, however correlation with surgical
outcome is less clear.
•
There
may be a ‘sweet spot’ for surgery – e.g. a score of 3 or 4 out of 6 may benefit
more than those who are more or less severe.
St Vincent’s Melbourne
|
Grade |
|
|
Very Mild |
Sensory (mixed) asymmetry >0.2ms and <2.2ms |
|
Mild |
Sensory asymmetry and absolute >2.2ms |
|
Mild-Moderate |
Motor latency asymmetry >1.5ms |
|
Moderate |
Motor latency >4.7ms (absolute) |
|
Moderate-Severe |
|
|
Severe |
Motor latency >6.2ms Axonal involvement: - Motor amplitude <5mV - Absent (or very low) sensory amplitude |
|
|
|
Canterbury Severity Scale for CTS
(Dr Jeremy Bland)
|
Grade |
|
|
0 |
Normal |
|
1 – Very Mild |
Asymmetry on sensory testing (2 of following): - Palm-wrist comparison - Lumbrical-Interosseous motor comparison - Digit 4 comparison - Inching study at wrist - Finger palm-palm-wrist comparison - Digit 1 comparison - Combined sensory index |
|
2 – Mild |
Digital sensory conduction velocity <40m/s (or prolonged digital
sensory latency) |
|
3 – Moderate |
CMAP latency >4.5ms (but <6.5) |
|
4 - Severe |
CMAP latency >4.5ms (but <6.5) AND Absent SNAP |
|
5 – Very Severe |
CMAP latency >6.5ms |
|
6 – Extremely severe |
CMAP amplitude <0.2mV |
(From: Muscle Nerve 23: 1280–1283, 2000)
Simple version
|
Mild |
Prolonged (relative or absolute) sensory studies. Normal Motor studies |
|
Moderate |
Prolonged motor distal latency |
|
Severe |
Axon loss – either: -
Absent
SNAP -
Low
amplitude or absent CMAP -
EMG
abnormality |
(From: Muscle Nerve 44: 597, 2011)
Treatment
Conservative treatment
•
Modify
activities
•
Neutral
wrist splint (especially at night)
Steroid injection
• Study
following up 211 of 273 patients who were initially treated with injection of
40mg methyprednisolone so their follow-up rate of 77%
is quite good for a study of this type.
•
The patients who were still satisfied
with the outcome were as follows:
o
6 months - 132 (63%)
o
12 months - 102 (48%)
o
18 months - 71 (34%)
•
They found that the length of remission
depended to some extent on the neurophysiological severity of the CTS before injection,
as follows:
o
'mild' (Canterbury grades 1 and 2) -
median time until relapse 15 months (60 patients originally injected)
o
'moderate' (Canterbury grade 3) -
median time until relapse 5 months (203 patients originally injected)
o
'severe' (Canterbury grades 4-6) -
median time until relapse 4.5 months (10 patients originally injected)
Surgery
- If severe wasting or no response to conservative
treatment
Anatomy
•
Entirely
C8-T1
•
Lower
trunk, Anterior division, Medial cord
•
Ulnar
groove
•
Cubital
tunnel
NCS
•
Routine
ulnar and median studies
•
Ensure
that below elbow stimulation is >3cm distal to medial epicondyle so it is
below the cubital tunnel
•
Recording
to FDI may be more sensitive
o
?The
FDI fibres may be on the side of the nerve more prone to compression
•
Dorsal
ulnar cutaneous
o
Record
over dorsal webspace between 4th and 5th
digits
o
Stimulate
just below ulnar styloid (80-100mm)
o
Normal
~>8uV
o
Compare
to other side – abnormal <50%
o
Helps
differentiate lesion at the wrist as it will be normal in this situation, c.f.
digit 5 SNAP which will be abnormal.
Ulnar neuropathy at the
elbow
•
Conduction
block
o
>10%
amplitude drop above elbow to below is probably significant
•
Slowing
>10m/s compared to forearm
•
Prolonged
ulnar F-M
•
If
axonal damage:
o
Reduced
SNAP or CMAP amplitude
o
Slightly
prolonged terminal motor latencies
EMG
|
|
Wrist |
Elbow |
Medial cord |
Lower trunk |
B8-T1 |
|
FDI |
|
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|
ADM |
|
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|
FDP (4,5) |
|
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FCU |
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APB |
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FPL |
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EIP |
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Paraspinals |
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Ulnar Neuropathy at the
elbow
Aetiology
•
Due
to repeated compression and stretch
•
In
cubital tunnel syndrome there is congential tight
tissue band which predisposes to compression
•
Chronic
compression of nerve at either:
o
Elbow
-
Ulnar
groove
-
Cubital
tunnel (formed by heads of FCU, starts 0-25mm below elbow)
-
Rarely
- Tumours, cysts, osteophytes, tissue bands
o
Wrist
DDx:
•
C8-T1
radiculopathy
•
Lower
cord plexopathy
•
Medial
trunk plexopathy
Clinical
•
Motor
o
Intrinsic
hand muscle weakness
o
Loss
of grip and pinch strength
o
Wasting
of thenar and hypothenar muscles
•
Sensory
o
Sensory
symptoms often minimal
o
Sensory
loss over 5th finger and half of ring finger
o
Loss
over medial palm – extending to but not past the wrist
•
Pain
at the elbow common, may be worse with flexion
Ulnar Neuropathy at the
Wrist
Radial
neuroapthy
- Commonly occurs at spiral groove
- Complete wrist and finger drop
- Numbness in the dorsolateral aspect of the hand
- Mild weakness of elbow flexion due to involvement
of supinators and brachioradialis
- Elbow extension unaffected as it is supplied by a
more proximal branch of the radial nerve
DDx
- Radial nerve palsy at the axilla (triceps
involved)
- Posterior interosseous neuropathy – rare
condition of posterior cord of brachial plexus
- C7 radiculopathy
NCS
Radial motor study to EIP
Superficial radial sensory
studies (bilateral for comparison)
EMG
|
|
Posterior Interosseous neuropathy |
Radial nerve: Spiral groove |
Radial nerve: Axilla |
Posterior cord |
C7 |
|
EIP |
|
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EDC |
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ECU |
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ECR-long head |
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Brachioradialis |
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Supinator |
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Anconeus |
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Triceps |
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Deltoid |
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Latissimus dorsi |
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FCR, Pronator teres |
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Cervical paraspinals |
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Abnormal radial SNAP (if axonal) |
|
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Low radial CMAP (if axonal) |
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Conduction block at spiral groove (if demyelinating |
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Conduction block b/n forearm and elbow (if demyelinating) |
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- See Brachial Plexus Injuries)
Peroneal neuropathy
Anatomy
•
L4-S1
•
Lumbosacral plexus – sciatic nerve
•
Biceps femoris
– short head – is the only muscle above the fibular neck supplied by the
peroneal division
•
Lateral cutaneous nerve of the knee
– braches off at level of knee – supplies sensation to proximal lateral calf
•
Winds around neck of fibular – into
fibular tunnel – between peroneus longus and fibula.
•
Divides into deep and superficial
•
Superficial branch
o
Motor
-
Peroneus longus
-
Peroneus brevis
o
Sensory
-
Continues as superficial peroneal to
supply distal calf onto dorsum of foot to the dorsal medial 3-4 toes up to IP
joints.
•
Deep branch:
o
Motor
-
Tibialis anterior
-
Extensor digitorum
longus
-
Extensor hallucis longus
-
Peroneus tertius
-
Extensor digitorum
brevis
o
Sensory
-
First webspace
between toes
•
Accessory
peroneal
o
15-20%
of people
o
Braches
off superficial peroneal and runs posterior to lateral malleolus to supply EDB
Clinical and aetiology
Peroneal neuropathy at fibular neck
•
Motor weakness of
o
Dorsiflexion of ankle
o
Dorsiflexion of toes
o
Eversion of ankle
o
Inversion of ankle is preserved
•
Sensory
o
Distal lateral calf and
dorsum of foot (some texts say less limited distribution)
o
Includes webspace b/n toes 1 and 2
•
Examination
tips:
o
If
EHL is affected more than TA this may suggest an L5 radiculopathy (as EHL is
more L5)
•
Aetiology:
o
Compression
-
Casts,
stockings, leg crossing
-
Often
seen in setting of weight loss
o
Trauma
o
Stretch
– forced ankle inversion
o
Entrapment
o
Mass
lesions – ganglia, baker’s cyst, tumour
Deep peroneal neuropathy at the ankle
•
Known
as “Anterior tarsal tunnel syndrome”
•
Compression
of the deep peroneal nerve under the inferior extensor retinaculum at the ankle
•
Foot
pain and paraesthesia in the first web space and weakness of EDB
•
Aetiology:
o
Tight
shoes
o
Bony
or other soft tissue abnormalities at the ankle
Superfical peroneal neuropathy
•
“Ski
boot neuropathy”
•
Compression
of distal, sensory component of superficial peroneal
•
Loss
of sensation over dorsum of foot to ankle
•
Aetiology:
o
Tight-fitting
boots
NCS/EMG
•
Compression
lesions at fibular neck are often purely focal demyelination
o
Focal
slowing across neck of >10m/s probably significant
o
Conduction
block may be seen
o
Superfical sensory should be normal in pure demyelinating
lesion
•
If
axonal loss is present
o
The
CMAP will be reduced at all sites
o
Superficial
sensory amplitude will be reduced
o
May
be hard to localise the lesion
o
Comparison
with other side important
•
Testing
deep peroneal to tibialis anterior may be more useful and reliable in many
patients
•
The
deep peroneal nerve is often more affected as it fibres run on the medial side
of the nerve as it passes by the fibular neck
•
EMG
|
Peroneal muscle
below fibular neck |
TA or EHL |
|
Peroneal muscle
above fibular neck – |
Biceps femoris (short head) |
|
Superficial
peroneal muscle |
Peroneus longus |
|
Sciatic,
non-peroneal, L5 muscle |
Tibialis
posterior or FDL |
|
Proximal L5
muscles |
Glut medius or TFL or L5 paraspinal |
DDx
•
L5 radiculopathy
•
Sciatic neuropathy
•
Lower lumbosacral
plexopathy
Lateral femoral cutaneous neuropathy
- Also known as meralgia paresthetica
- Results in paresthesia/burning
sensation over lateral thigh associated with numbness
- No weakness
- Worse with standing and
walking, relived by hip flexion
- Causes
- Obesity
- Tight clothes
- DM
- Pregnancy
- Gradual onset of burning pain in ankle and sole
of foot
- Wasting of intrinsic foot muscles
- Strength testing often normal
- Entrapment of the distal tibial nerve under the
flexor retinaculum at the medial ankle posteriorly
- Pain and tenderness in the buttock at the sciatic
notch
- Often radiating down the leg
- Absence of back pain
Interdigital Neuropathy (Morton’s Neuroma)
- Local pain and numbness on the ball of the foot
between the 3rd and 4th toes
- Other toes may be less commonly involved
- Caused by chronic repetitive compression of the common
plantar digital nerve between the third and forth
metatarsal heads and the transverse metatarsal ligament.
-
|
|
Record |
Stimulate |
|
|
|
Radial Motor |
EIP Active - 2 FB proximal to ulnar styloid on posterior forearm Ref – ulnar styloid |
Forearm: Over ulnar 4-6cm proximal to active Elbow: In the groove between the biceps and brachioradialis Below spiral groove: Lateral mid arm between biceps and triceps Above spiral groove: Posterior proximal arm over the humerus |
|
|
|
Radial Sensory |
Superficial radial nerve G1 – extensor tendons of thumb G2 – Distal thumb |
Distal mid radius – 10cm |
|
|
|
Median antebrachial cutaneous |
Medial elbow: midpoint between the biceps tendon and medial epicondyle |
Medial forearm – on line between recording site and ulna styloid – 12cm |
Medial cord Lower trunk |
|
|
Lateral antebrachial cutaneous |
Antecubital fossa – slightly lateral to the biceps tendon |
Lateral forearm – on line between stimulator site and the radial wrist – 12cm |
Musclocutaneous nerve Lateral cord Upper trunk C6 |
|
|
Deep ulnar motor branch study |
FDI G1 over muscle belly G2 over MCP joint of thumb |
Usual ulnar sites: wrist (8-12cm), below elbow and above elbow |
|
|
|
|
Stimulation |
Record |
Distance |
Significant result |
|
Palm-wrist |
Median palm Ulnar palm |
Median wrist Ulnar wrist |
80mm 80mm |
>0.2 [>0.4] |
|
Digit 4 sensory |
Median wrist Ulnar wrist |
Digit 4 Digit 4 |
110mm 110mm |
[>0.5] |
|
Lumbrical-interossei |
Median wrist Ulnar wrist |
Palm b/n 2nd and 3rd MC (ref on dig 2) |
100mm 100mm |
[>0.5] |
|
Radial comparison |
Median wrist Lat. radius |
Digit 1 Digit 1 |
100mm 100mm |
[>0.5] |
|
Segmental sensory study |
Median wrist Median palm |
Digit 3 Digit 3 |
130mm 65mm |
CV difference >10ms* |
* Need to calculate conduction velocity using formula A= (BxC)/((2xB)-C) where C = wrist to digit 3 velocity and B =
palm to digit 3 velocity.