nerve Flashcards
TMR transfers
hand closing: Median -> short head biceps
hand opening: radial -> lateral head triceps
ulnar -> brachialis (if long limb)
musculocutaneous -> lateral biceps (native)
digit and wrist extension: proximal radial -> long head triceps (native)
brachial plexus birth palsy nerve involvement
C5-C6 affects deltoid, rotator cuff, biceps, ECRL, ECRB (erbs palsy)
C7 triceps, ECU and finger flexion (waiters tip)
C5-T1 flaccid arm
global injury with horners syndrome from sympathetic chain involvement has poor prognosis (indicates avulsion). will have ptosis.
prognosis brachial plexus birth palsy
70-80% full recovery
Antigravity elbow flexion <3 months then full recovery
> 6 months no recovery then need surgery
global injury the surgery early
treatment brachial plexus birth palsy
neuroma excision with sural nerve graft
nerve transfers
contractures in brachial plexus birth palsy
shoulder abduction, internal rotation, elbow flexion and supination contractures
glenohumeral dysplasia
- treat supination contracture with biceps rerouting
- treat elbow contracture with bracing
scapular winging
medial scapular winging - long thoracic nerve and serratus anterior muscle. Nerve arises from nerve root so injury suggests preganglionic. C5, C6 and C7.
lateral scapular winging - trapezius and/or rhomboid dysfunction
scratch collapse test
peripheral nerve can experience allodynia with external stimulus applied at or near an area of compression or injury -> temporary inhibition of tonic muscle contraction called “cutaneous silent period”. May be through inhibitory spinal reflex.
radial nerve anatomy
C5-T1
deep motor branch and superficial sensory in forearm
motor gives off ECRB before Arcade of Frohse (supinator arch) to become PIN.
motor branch median nerve
most common three terminal branches to APB, OP and FPB but variability
hoffmans sign
hold long finger in extension and snap fingernail into flexion. If spontaneous flexion index and adduction of thumb then upper motor neuron injury.
muscular dystrophy
- genetic disease of muscle (not nerve)
- progressive wasting and hypotonia
myasthenia gravis
- autoimmune disorder of acetylcholine receptors at the neuromuscular junction
- weakness and rapid fatigue of muscles under voluntary control
stain motor axons
acetylcholine esterase
stain sensory axons
carbonic anhydrase
conduit indications
<3mm gap (better if less than 1.5mm)
tend to collapse
major mixed nerve defect
sural nerve cable graft
CT myleogram/MRI in brachial plexus
3-4 weeks after injury can detect pseudomeningocele if avulsion injury
associated injuries with brachial plexus
- rotator cuff 10%
- spinal cord 10%
- SAN 6%
- vascular 20%
- rib fracture (92% still have function intercostal nerve function)
surgery timing brachial plexus
3-6 months ideal
18 months before motor end plates degenerate
options for elbow flexion
- ulnar/median fascicle to biceps/brachialis branch
- graft C6 to anterior trunk or MCN
- intercostal to MCN
- SAN to MCN
- free gracilis
options for shoulder abduction and external rotation
abduction - triceps to anterior branch of axillary nerve - graft C5 to posterior division of upper trunk - graft C5 to posterior cord - graft C5 to axillary nerve - medial pectoral to axillary nerve external rotation - SAN to suprascapular nerve
reconstruct grasp
- free gracilis to FDP
reconstruct elbow extension
- intercostal to triceps
- SAN to triceps
risk factors compression neuorpathy
- DM
- hypothyroid
- obesity
- recent menopause
- trauma (DRF)
- pregnancy
- renal disease
- inflammatory arthritis (RA, gout)
median nerve anatomy
- run with brachial artery through the arm (no branches before the elbow)
- medial to brachial artery at the elbow
- splits 2 heads of pronator teres
- between FDS and FDP
- palmar cutaneous branch proximal to carpal tunnel (5-6 cm proximal to wrist crease)
- motor branch runs radially to the thenar muscles
carpal tunnel syndrome
- 0.1-10% of the population
- distal sensory latency >3.6ms
- motor latencies >4.2ms
- steroid injection 22% symptom free at 12 month, 40-80% short symptom improvement
- revision surgery 50% get relief
AIN compression
- motor without sensory symptoms
- divides from the median nerve 4-6 cm distal to the elbow
- passes between 2 heads of PT
- innervates FDP IF and MF, FPL, PQ
- can be seen in parsonage-turner syndrome
pronator syndrome
- pain in the forearm +/- weakness
- will have numbness of the thenar eminence
- ligament of struthers, lacertus fibrosis and fascia of the superficial head of the arch of the proximal FDS
radial nerve anatomy
- C5-8
- around the spiral groove of the humerus
- run with profunda brachii artery
- pierce lateral intermuscular septum between brachialis and brachioradialis
- anterior to lateral epicondyle
- divides to deep PIN to extensor muscles (except mobile wad) and superficial between BR and ECRL to sensation of the dorsal radial hand.
PIN syndrome
- wrist extends with radial deviation due to intact ERCL, no active MCP extension
- associated with hypertrophic bursa, radial head dislocation
- usually treat conservatively 12 weeks before consider surgery
radial tunnel syndrome
- pain over mobile wad in dorsal forearm at site of PIN without weakness
- easily confused with lateral epicondylitis
- five anatomic sites of compression in the radial tunnel:
1. fibrous bands between the brachialis and brachioradialis
2. leash of Henry comprised of the recurrent radial vessels overlying the PIN at the radial neck
3. edge of the ECRB
4. arcade of Frohse at the proximal superficial supinator (most common site of compression)
5. distal supinator. - middle finger test
- EMG/NCS not helpful
Wartenbergs syndrome (cheralgia paresthetica)
- sensory branch of radial nerve compression
- BR and ERCL compress with forearm pronation
- handcuffs, watches, bracelets can bring on
- conservative treatment 70% success
- surgery involves release of fascia, neurolysis, dequervians release
ulnar nerve anatomy
C8-T1 to medial brachial artery
- run behind epicondyle
- no branches until the elbow joint
- between two heads FCU
- between FCU and FDP
- Guyons canal divide to superficial sensory and deep motor
- dorsoulnar to ulnar artery
ulnar nerve innervated muscles
FCU, FDP (ring and small), hypothenar (AbdDM, ODM, FDM), 3rd and 4th lumbricals, dorsal interossei, palmar interossei, thenar muscles (AddP, deep head FPB)
cubital tunnel compression points
- arcade of struthers
- medial intermuscular septum
- medial epicondyle
- cubital tunnel
- deep aponeurosis FCU
fromens sign
over FPL with pinch due to loss of first dorsal interosseous and adductor pollicis from ulnar nerve weakness. jeannes sign is MCP hyperextension.
failed cubital tunnel release
- worse results with previous submuscular transposition, age >50, EMG with dennervation, alcohol use, DM, CRPS
zones of guyons cannal
- zone I proximal. motor and sensory. ganglion, fx of hamate/radius
- zone II motor nerve. ganglion
- zone III sensory impairment. ulnar artery thrombosis, anomalous muscles
nerve transfer axons
need at least 30% axon count to recover muscles function
- SAN 1300-1600 to SSN 3500
- long head triceps 2300 (slightly less than medial head) to axillary 4000
- ulnar 1300 to brachialis 1800
- median 1900 to biceps 1800
- AIN 900 to ulnar motor 1200
radial nerve transfers
FCR to PIN (can get individual finger extension)
FDS to ECRB
sarcomere length
2.6-2.8 micrometers is natural resting length
can measure intraoperatively with laser diffraction
tenodesis
increases excursion 20-30mm
wrist flexion -> finger extension
wrist extension -> finger flexion
radial nerve palsy
- BR and ECRL branch above the elbow
- PT to ERCB
- FCR to EDC (sub vs interosseous membrane)
- PL or FDS ring to EPL
median nerve palsy high vs low
high includes AIN (PT/PQ, FCR, FDS, FDP index & middle)
low - only FPL, thenar (opponens, APB, 1/2 FPB (superficial))
opponensplasty
- may not be necessary if riche-cannieu anastomosis and ulnar innervation
- may need to deepen first webspace
- donor options to transfer to APB:
- PL with palmar fascia pulley. abduction movement more than opposition
- -EIP is weak
- FDS not synergistic and only available with low palsy
- -ADM use for congenital
- -ECU
- -FCR
median tendon transfers
- opponensplasty to APB
- restore pronation with biceps rerouting
- FDP ring/small to FDP index/middle side to side or ECRL to FDP index middle
- BR to FPL
ulnar nerve palsy
- high - FCU and FDP ring/small
- low - hypothenar, lumbricals 3rd and 4th, interossei, adductor pollicis, FPB
- grip decreased 50-75%
- clawing of SF, RF due to extrinsics extend the MP and flex IPs. IF and MF spared due to median contribution to 1st and 2nd lumbricals
- Wartenberg sign - SF abduction due to unbalanced EDM
ulnar tendon transfers
- FDP tenodesis
- for clawing:
- -MP capsulodesis - advance the volar plate proximal
- FDS zancolli lasso (suture FDS to A1 pulley)
- FDS3 to radial lateral bands (pass volar to transverse intermetacarpal ligaments)
- -ECRL with 4 tendon grafts to lateral bands (ulnar to index and radial other digits)
- for small finger abduction due to unbalanced EDM on the ulnar aspect of the extensor hood:
- -if no clawing then route through 4th webspace to radial collateral ligament of the MP joint
- -if clawing route through the 4th to 5th metacarpal interspace, volar to the transverse intermetacarpal ligament to radial proximal phalanx or A1 pulley
- key pinch
- -FDS3/4 or ECRB to adductor pollicis
- -APL slip (or EIP or EPB) to first dorsal interosseous
Bouvier sign
manually block the MP joint and ask to extend the PIP. If can then central slip and lateral bands are intact (positive test) and can do a passive tendon transfer.
tetraplegia
- lateral pinch and palmar grasp most important
- create wrist tenodesis then add strength
- 50-60% meet criteria (must have motivation, reasonable goals, neurologic stability)
international criteria for surgery of the hand in tetraplegia
based on >M4 strength 0 no grade 4 below the elbow 1 BR 2 BR + ECRL 3 above + ECRB 4 above + PT 5 above + FCR 6 above + finger extensors 7 above + thumb extensors 8 above + partial digital flexors 9 lacks only intrinsics - triceps +/- - sensory O (oculer) vs Cu (cutaneous) if 2PD in thumb/index <10mm
tetraplegia elbow extension
- posterior deltoid -> triceps (get M3)
- biceps -> triceps (get M4, preferred)
tetraplegia lateral pinch
- CMC arthrodesis in opposition
- radial FPL to EPL split tendon transfer for IP stabilitization
- EPL tenodesis
- BR ->FPL
palmar grasp 2 stage procedure
stage 1 positioning and extension
- intrinsics for MCP flexion and IP extension with tenodesis
- finger extensors tenodesis vs transfer
stage 2 flexion (2-6 months later)
- FDP flexion with ECRL donor
tetraplegia nerve transfers
- SPIN transfer - supinator to PIN for extension
- BR or ECRB to AIN/FDS
tendon weaves
Brown side to side tendon weave stronger than pulvertaft and allows earlier movement.
lumbrical anatomy
The index and middle finger lumbricals are unipennate muscles originating from the radial side of the FDP tendon. The ring and small finger lumbrical muscles arise from bipennate muscle bellies on the adjacent surfaces of the FDP tendons. These pass volar to the transverse intermetacarpal ligament (TIML) or interpalmar plate (Figure 1) and insert distally into the radial side of the lateral band of the extensor tendon. From origin to insertion, the lumbricals transition from a volar to dorsal location. Similar to the FDP muscles, the nerve supply of the four lumbrical muscles is from two sources. The index and middle finger lumbricals are innervated by the median nerve (or digital nerve), whereas the ring and small finger lumbricals are innervated by the deep division of the ulnar nerve.
Hereditary neuropathy with liability to pressure palsies (HNPP)
considered in patients who present with recurrent multifocal compression neuropathies. It is an autosomal dominant disease that most commonly affects the median, ulnar and peroneal nerves with generalized demyelination with reduced conduction velocities at sites of entrapment. The usual age of onset is between 10 and 30 years of age. The entrapment neuropathies often resolve within hours to months. Therefore, a trial of conservative treatment with occupational therapy may be valuable especially in children.
- genetic testing is notable for a deletion on chromosome 17 resulting in abnormal peripheral myelin protein 22 (PMP22).
parsonage-turner syndrome
- neuritis of the brachial plexus
- causes suggested viral, trauma, strenuous activity, surgery
multiple sclerosis
autoimmune against myelin of central nervous system
charcot-marie-tooth disease
- inherited neuropathies affect sensory and motor nerves
- progressive muscle weakness
- involved hands and feet
amyloid
- 10% if bilateral carpal tunnel syndrome >50 years (men) or >60 years (women)
- biopsy stain congo red (apple green birefringence) or thioflavin
- refer to cardiology
- characteristics: spinal stenosis, biceps tendon rupture, a fib, pacemaker, congestive heart failure
Schwann cell role in axon regeneration
1-clearance of myelin debris (i.e., Wallerian degeneration)
2-produce neurotropic factors such as nerve growth factor (NGF)
3-proliferate to line the bands of Büngner, which are tubes that accept and guide the regenerating neurons
4-secrete fibronectin and laminin, which help the growth cone adhere to the basal lamina of the endoneurial tubes
5-remyelinate the new axonal outgrowths
process of nerve regeneration
Wallerian degeneration starts 24-36 hours after injury in the axon distal to the point of injury. The axolemma (nerve cell membrane) and axon cytoskeleton degenerate. Schwann cells dedifferentiate into non-myelin producing cells, clear the myelin debris, and proliferate to line the remnant of the endoneurial tube (bands of Büngner). It is the bands of Büngner which line up the dedifferentiated Schwann cells along the basal lamina of the remaining endoneurial tube to provide a path for the regenerating axon.
The proximal nerve stump dies back to the nearest node of Ranvier (i.e., gap in the myelin sheath that allows faster/saltatory conduction). There it forms a growth cone from which projects multiple filopodia. Nerve growth factor (NGF), which is secreted by the Schwann cells in the bands of Büngner, attracts these regenerating nerve sprouts, guiding them to the target organ with remyelination.
lateral anebrachial neuritis
irritation of lateral antebrachial cutaneous nerve along the lateral edge of the biceps tendon. Dysesthesias in the volar forearm and thenar region.
nerve ansastomoses
- Martin-Gruber anastomosis, which is a motor fiber interconnection between the median nerve and ulnar nerve in the proximal forearm.
- Riche-Cannieu anastomosis is a motor interconnection between the deep branch of the ulnar nerve and the recurrent branch of the median nerve in the hand, which leads to variable innervation of the thenar muscles by the ulnar nerve.
- Marinacci anastomosis is a motor interconnection between the ulnar nerve in the proximal forearm to the median nerve in the distal forearm. This is also referred to as a reverse Martin-Gruber anastomosis.
- Berrettini anastomosis is a sensory communication between the third common digital nerve from the median nerve and the fourth common digital nerve from the ulnar nerve. This interconnection typically occurs proximal to the transverse carpal ligament.
- Froment-Rauber anastomosis is a posterior interosseous nerve or the superficial radial nerves continue distally and provide motor axons to the first (and sometimes the first through third) dorsal interossei muscles
