• Nerve Anatomy:
• Pacinian corpuscles: detect vibration in subcutaneous tissue, myelinated A-beta fibers
• C fibers: burning pain
• A-delta fibers: sharp pain
• Meissner’s corpuscles: intermediate dermal ridge–> moving two point discrimination a beta
• Merkel cell: static two point discrimination (sweat ducts) interdermal ridge a beta
• Nerve Repair:
• Sunderland I neuropraxia II, III, IV axonotmesis with complete then variable recovery , V complete transection neuronotmesis no recovery -VI is segmental nerve injury
• EMG findings occur after 3 weeks
• Age is the best predictor of outcomes for nerve repair
• Nerve injuries and open wounds: if clean should repair early, if crush or significant injury should wait for 6 weeks then repair (especially GSW), 6 weeks, EMG –> motor end plate potential –> wait (3 months requires surgery with nerve graft of nonfunctioning part including neurolysis if in continuity)
• Primary repair can be completed in clean lacerations less than 1cm gap; 
• Autograft now after 7 cm not 3 (still tested on 3)–> if less than these limits may use allograft, conduits can be used for less than 3cm (0-3cm conduit, 3-7cm allograft, 7+ autograft)
• For repair on nerve with tension, polyglycolic acid conduit better than nerve graft at time of repair
• Neuroma in continuity: nerve conduction velocity studies performed intraoperatively to identify non-functioning fascicles 
• microdissect the neuroma with EMG of motor fascicles if sensory deficits only
• Neuroma (not in continuity) excision followed by sural nerve grafting; 
• Nerve grafting in hand: digital nerve best suited with terminal branch of posterior interosseous nerve, no sensory deficits, lies on floor of fourth extensor compartment deep and ulnar to EPL, only need one strand;
• Severely comminuted humeral fractures with nerve gap: may shorten humerus with primary repair of nerves (ideally end-end); shoulder  abduction increases length of medial ulnar nerve 2cm, elbow flexion ulnar/median nerve 4cm
• Repair nerves at time of injury to prevent scarring
• Conduits can be used for defects <4cm (not on major peripheral nerves)
• Interfascicular sural nerve repair can be used if shortening not an option
• Does not need nerve transfer if repairs can be obtained (if distal ends are available for use)
• Compression Neuropathy is nerve entrapment- disproportion between volume of nerve and space through which it passes
• Acute vs chronic
• 30mmHg- paresthesias
• 50-60mmHg- complete motorsensory block
• Local nerve ischemia prevents depolarization (-90 is resting)
• Pathophysiology: elevated extraneural pressure inhibits intraneural microvascular blood flow –> decreased axonal transport –> endoneurial edema –> demyelination, distal axon degeneration –> fibrosis
• Degree of axonal injury proportional to duration and magnitude to compression
• Electrodiagnostic testing: 
• Nerve conduction study –> segmental demyelination –> slowed nerve conduction
• Electromyography: good for axonal loss
• Associations: Diabetes, Hypothyroid, Obesity, Recent Menopause
• Median Nerve: accompanies brachial artery through arm –> no branches until elbow –> medial to brachial artery at the elbow –> splits the two heads of PT –> –> FDS/FDP –> becomes superficial 5cm proximal to wrist FDS and FCR –> distal forearm 20% motor; 80% sensory; motor nerves leave volar 
• FOAL : innervated by recurrent median nerve: FPB (one head), opponens pollicis, abductor pollicis brevis, lateral two lumbricals
• Recurrent motor branch-runs radially to thenar muscles–> 3 variations (extraligamentous, intraligamentous, transligamentous) 
• ALL FOR ONE AND ONE FOR ALL lateral to medial intrinsic muscles of thenar and hypothenar
• Pad Dab for intrinsics
• Palmar cutaneous branch arises proximal to TCL (PL and FCR) –> originates 5cm proximal to wrist flexor crease
• Carpal tunnel contents: median nerve, 9 flexor tendons. Roof is TCL, floor is radiocarpal ligaments, borders include scaphoid and trapezium radially, triquetrum and hamate ulnarly
• Carpal Tunnel Syndrome: most common compressive neuropathy 
• History: intermittent to constant paresthesia in median distribution (particularly at night), pain frequent (may radiate proximally), decreased dexterity, weakness/atrophy late
• Associated: DM, HT, pregnancy, renal disease, inflammatory arthritis, trauma, masses, amyloidosis
• Staging: Early (mild): intermittent paresthesias, pain, night symptoms; Intermediate (moderate): more frequent paresthesias, worse with use, numbness, clumsiness; Advanced (severe): constantly impaired sensibility, severe pain, thenar atrophy, pinch opposition weakness
• Acute CTS: after fracture, spontaneous hemorrhage, thrombosis of persistent median artery, pyogenic infection –> delay of 36 hours of release may result in poor prognosis
• Release of TCL releases guyon’s canal (89%) with ulnar symptoms have relief
• Physical Exam: Thenar atrophy, test APB, pinch strength
• Sensibility: sever nerve- 2 point, compression- semmes weinstein (more sensitive and specific- 85-90%)
• Provocative tests: Durkans is the most sensitive and specific –> compression at carpal tunnel
• Phalens, tinel’s (wrist flexion and tapping on nerve from distal to proximal)
• EMG/NCS: Abnormal nerve latency >4ms
• Diagnostic Ultrasound: look at transverse images (look at area of median nerve in carpal tunnel and median nerve proximal), ratio of the two
• Treatment: 
• Nonoperative: night splints (wrist neutral), steroid injections
• Steroid Injection: 40-80% may get relief from days to months with eventual recurrence (usually 4-6 weeks), inject ulnar to median nerve, most successful in patients with mild symptoms
• Nonsurgical treatment for carpal tunnel works in short term but not long term
• Surgical indications: failed nonoperative treatment, constant symptoms, weakness, motor denervation with EMG
• Surgery: open TCL (on the ulnar side), Endoscopic CTR (rehabs faster); Open technique for carpal tunnel has decreased recurrent median nerve injury
• Complications: incomplete release, damage to PCB, hypertrophic painful scar, bowstringing of tendons, RSD?
• Splints are not necessary, therapy not necessary, abx not indicated in pre or post op (only selected DM, immunocompromised)
• Revision carpal tunnel release –> 50% improve, adjunctive procedures include hypothenar fat pad flap, radial forearm fascial flap, radial artery perforator based flap (to prevent scarring)
• AIN: Anterior interosseous nerve —> motor nerve –> divides from median nerve 4-6cm distal to elbow –> passes between 2 heads PT
• Innervates FDP index and long, FPL, PQ hard to test
• Sites of compression: deep head PT, edge of lacertus fibrosis, enlarged bicipital tendon bursa, FDS arcade, accessory head of FPL (Gantzer’s muscle), aberrant radial artery, thrombosed ulnar artery
• AIN Compression: motor loss without sensory involvement, inability to perform OK sign, may have some intrinsic muscle palsy, test resisted pronation with elbow maximally flexed
• Remember martin gruber anastomosis (ulnar/median nerve anastomosis in forearm)
• Riche cannieu in hand
• Presentation: complete vs incomplete, spontaneous onset of pain in proximal forearm, unable to actively flex thumb IP and index long DIP, weak forearm pronation, bilateral RARE
• Incomplete: isolated FPL or FDP index
• Treatment: depends on etiology –> traction (observe), traumatic –> explore
• Surgery: lacertus fibrosis release, PT release, FDP fibrous arch release
• Prontator Syndrome: pain proximal forearm +/- weakness, paresthesias in median nerve distribution (including thenar eminence)
• Physical exam: tinels, motor weakness, diminished sensibility 
• EMG/NCV: usually normal
• Etiology: fibrous band (ligament of struthers), lacertus fibrosis, pronator muscle, fibrous arch FDS
• Treatment: splinting, activity modification
• Surgery: 90% successful –> release ligament of struthers, supracondylar process of humerus, lacertus fibrosis, fascia of superficial head of pronator arch of proximal FDS
• Radial Nerve: C5-8,T1; spirals around posterior aspect of humerus with profunda brachii artery (13cm proximal to trochlea) –> pierces lateral intramuscular septum (7.5cm proximal to trochlea, between brachialis and brachioradialis) –> anterior to lateral epicondyle
• Divides into superficial and deep branches (PIN and SBRN)
• PIN: splits supinator muscle, innervates extensors (except mobile wad- BR, ECRL)
• (PIN) bt EDC and ECRB in forearm
• PIN innervates from ulnar to radial (ECU first, most distal innervation is EIP**), terminates under fourth extensor compartment to innervate wrist capsule
• SBRN: between brachioradialis and ECRL –> sensation to dorsal radial aspect of hand –> SBRN runs below the brachioradialis in mid forearm –> becomes subcutaneous 8-9cm proximal to the radial styloid, piercing the fascia

The radial nerve may be compressed at one of five points in the radial tunnel: 

• The fascia adjacent to the radiocapitellar joint  
• The recurrent radial artery/Leash of Henry  
• The tendinous margin of the ECRB  
• The leading edge (fascial band present in 30%) of the supinator muscle (Arcade of Frohse). Typically found 5 cm distal to the lateral epicondyle.
• The distal (dorsal) aspect of the supinator muscle
• Radial nerve palsy: associated with tourniquet use, most commonly affected (pressure beneath cuff), permanent deficits rare –> resolution of symptoms in 6 months
• Posterior Interosseous Nerve Syndrome (PINS):weakness/pain in forearm in absence of sensory loss; weakness of extension at MP/PIP joints, thumb abduction and wrist extension, wrist  deviates radially because ECRL (innervation lies above elbow), progressive muscle atrophy

• Presentation: progressive loss of extensors –> wrist extends in radial deviation, cannot actively extend MCPJ, pain not a major complaint
• Differential diagnosis: includes RA tendon ruptures
• Etiology: entrapment of elbow, masses (ganglion,lipoma, bursa), radial head dislocation
• Treatment: conservative 8-12 weeks –> activity modification, splint, steroid

• Surgery: anterior, BR splitting, BR/ECRL interval, EDC/ECRB interval, transverse (approaches)
• Radial Tunnel Syndrome: pain over anterolateral aspect of elbow, increases with passive pronation/wrist flexion or active supination/wrist extension; night pain, no sensory/motor disturbance, may co-exist with tennis elbow
• Sites of compression: fibrous bands, vascular leash, ECRB, proximal supinator, distal supinator, arcade of Frohse (pin entrapment)
• Exam: pain over PIN (lateral humerus and elbow, extensor mass, dorsal wrist), provocative tests (middle finger test– resisted extension of middle finger), resisted supination
• EMG/NCV not usually helpful
• Treatment: conservative –> activity modification, splinting, injection
• Surgical release
• Cheralgia Paresthetica (Wartenberg’s Syndrome): SBRN entrapment
• Etiology: compression external (jewelry), BR/ECRL –> with pronation of forearm
• Radiodorsal hand: pain, numbness, paresthesias
• Provocative Tests: tinel’s over nerve, pain with pronation
• Treatment: conservative management –> modification, no jewelry, steroid injection
• Surgery: 80-85% successful, release deep fascia around nerve +/- Dequervain’s release
• Ulnar Nerve: C8-T1 (C7); runs medial to brachial artery then behind medial epicondyle –> no branches in arm until elbow –> enters forearm between 2 heads FCU –> between FCU/FDP –> crosses wrist in Guyon’s canal –> divides into superficial and deep branches

• Ulnar and volar to ulnar artery
• Ulnar motor: FCU, FDP (III and IV), PB, hypothenar muscles, 3/4 lumbricals, dorsal interossei, palmar interossei, thenar muscles AddP and deep head FPB
• Ulnar nerve anatomy: motor function is ulnar and dorsal to sensory group at wrist, in arm motor fascicles between sensory fascicles 

• Proximal to the wrist crease the nerve can be topographically mapped –> palmar radial fibers become superficial branch and dorsal ulnar become deep motor branch
• DSBUN branches 6cm proximal to the ulnar head to supply the ulnar dorsum of the hand
• Sensation to ulnar half of hand (half ring and small)
• Wartenberg sign: abduction of the little finger (ulnar clawing due to low ulnar nerve injury), hyperflexion of the IP joint of the thumb, atrophy of the intrinsics, 
• Active and passive correction of clawing: can attempt if bouvier test is positive (slightly flexing MP to see if IP extend)
• Flexion at small finger MP joint by FDM, adduction of thumb by ulnar nerve (last to return)
• High ulnar nerve injuries (anything proximal to FCU and FDP): unsatisfactory results with minimal return of intrinsic function  motor endplates become refractory to reinnervation 15-18 months, sensory is adequate, can transfer AIN to deep branch of ulnar nerve (shorter distance), loss of pronator function insignificant
• Low ulnar nerve injuries cause clawing due to paralysis of intrinsic with unopposed flexors and extensors (extension at MP, flexion at IP)
• Ulnar nerve injury at elbow: If there is a gap in repair can perform transposition (up to 4cm in length); 3 in arm, 2 at forearm 1-2cm at wrist
• Cubital Tunnel Syndrome: intermittent paresthesias in the ulnar 2 digits, sensory loss later, extrinsic/intrinsic motor weakness (FDP to ring and small), may have mild clawing
• Potential sites of compression: arcade of struthers, medial intermuscular septum, medial epicondyle, cubital tunnel (osbornes ligament), deep aponeurosis of FCU, triceps, aconenous epitrochlearis (anomalous muscle)
• Physical exam: atrophy, motor strength, sensibility, tinel’s, elbow flexion test (provocative maneuver), look for nerve subluxation with elbow flexion (when it comes out of retrocondylar groove)
• Cubital tunnel should have some sensory loss on dorsum of hand (differentiate from Guyon’s)
• Dorsal interossei wasting, wartenburg SIGN (ulnar clawing), froment sign (ask to grasp paper –> will grasp with IP joint of thumb instead of dorsal interossei), pyramid sign –> loss of intrinsics in the hand
• Treatment: conservative: elbow splint (45 extension)
• Surgery: in situ decompression, anterior transposition (subcutaneous, submuscular, intramuscular), medial epicondylectomy (none are superior to the other)
• In situ decompression: safe and simple (release the sites of compression only, do not change its position), do not perform if nerve subluxates
• Transposition: severe ulnar neuropathy, failure of in situ, throwing athlete, angular deformities, subluxation of the nerve ** must remove some medial intramuscular septum if you transpose
• Complications: elbow flexion contracture, medial epicondylitis, neuroma of the (MABCN), elbow instability, persistent m/s deficits, failed decompression
• MABC can be injured during ulnar nerve neuroplasty, best identified and corrected by excision of neuroma and nerve stump implantation
• Indications for re-op: pain, progressive worsening, unchanged neurologic defect
• Ulnar Tunnel Syndrome (Guyon’s canal): divided into 3 zones –> zone of compression correlates with symptoms
• Distal ulnar tunnel is 4.5cm in length, entrance is proximal edge of volar carpal ligament, exit is distal margin of fibrous arch
• Roof: VCL; floor TCL ,flexor retinaculum; lateral wall: hamate, TCL; medial wall: ADM and pisoform/pisohamate ligament
• Presentation: numbness/paresthesias in palmar aspect ring and small (NOT DORSAL- dorsal hand divides proximal to wrist crease); weakness/atrophy (ulnar intrinsics)
• Sites of compression: palmaris brevis, fibrous origin of FDM, ulnar artery aneurysm or thrombosis, hook of hamate fracture, ganglion cyst (most common)
• Zones: 
• 1 begins at proximal edge of volar carpal ligament, proximal to pisiform and ends at nerve bifurcation –> both m/s –> usually combines paresthesias and weakness, less commonly to have isolated s/m findings, ganglion 86%, fracture of hamate
• 2 deep motor nerve –> travels around the hook of the hamate and between hypothenar muscles: usually present with isolated motor, ganglion most common
• 3- remains superficial to innervate PB: sensory impairment alone (ulnar artery thrombosis)
• Evaluation: Xrays with carpal tunnel view, CT/MRI, EMG/NCV –> if hamate hook is broken excision may be performed as treatment
• Treatment: conservative if repetitive trauma, no mass, idiopathic; surgery: refractory or identifiable cause
• Double Crush Syndrome: compression in neck and at other distal site –> should release distally anyway
• Treat peripheral site first
• Brachial Plexus
• Anatomy (Real Texans Drink Cold Beer)- Roots, Trunks, Divisions, Cords, Branches
• C5-T1
• Long thoracic nerve comes from C5-C7 roots
• Trunk: (upper, middle and lower) 
• Upper trunk C5-C6 otherwise known as erb palsy –> weak or absent elbow flexion, shoulder abduction, and external rotation) 
• “waiter’s tip posture”- spares lower trunk
• Brachial plexus palsy:  C5-C6 use biceps as predictor –> if some function at 2 months will likely have normal arm function –> no function at 6 months bad prognosis (operate 3-6 months)

• C5-C6 lesion with supination deformity –> redirect biceps tendon through interosseous membrane (biceps tendon is strongest supinator in arm) –> then attach to itself
• Complete tetraplegia at C5, elbow extension most useful (deltoid/triceps and biceps to biceps)
• Suprascapular nerve- is the first branch off of the upper trunk –> symptoms of inury include diffuse posterior shoulder pain, atrophy of supraspinatous/infraspinatus; weakness in external roation of shoulder
• External rotation provided by supra and infraspinatus –> spinal accessory nerve to suprascapular nerve transfer
• Middle Trunk
• Lower Trunk
• Divisions
• Cords
• Lateral cord from C5-C7 and contributes to median and MSK nerves, pectoral nerves
• Biceps function, supination, finger flexors
• Medial cord from C8-T1 –> gives fibers to medial pectoral nerve, MABC, and contributes to median and ulnar nerves
• Intrinsic innervation
• Posterior cord from C5-C8, contributes to axillary, thoracodorsal nerve, subscapular radial nerve
• (latissimus) adduction, shoulder extension, internal rotation
• Branches: 
• Median
• Brachialis branch from MSK or ECRB branch from PIN can be transferred for AIN
• Ulnar nerve c8-t1,
• AIN to ulnar nerve for ulnar nerve palsy (for intrinsic function) (use for high ulnar nerve injuries)
• Radial
• Axillary: nerve arises from posterior cord (C5-C6) giving off branches to teres minor and deltoid (shoulder abduction) –> can be seen in glenohumeral joint dislocations, proximal humerus fractures or arthroscopy

• Axillary nerve Transverses through quadrangular space
• Nerve to triceps (radial) to axillary nerve
• MSK nerve: provides motor axons to brachialis, biceps brachii (strongest supinator, and provides elbow flexion), coracobrachialis

• Remember LABC continuation of MSK in the forearm (lateral arm sensation)
• Laceration to musculocutaneous nerve:  can transpose ulnar nerve to biceps and median to brachialis
• (Oberlin Transfer) For elbow flexion may do FCU to MSK or median nerve to brachialis 
• Syndromes:
• Thoracic outlet syndrome:  pain in right upper chest and back, intermittent coolness of the hand, numbness and tingling of her right ring and little fingers. Positive Adson test (compression at scalenes resulting in loss of radial pulse) and positive Roos (elevated arm) test
• treatment is resection of first rib, scalenectomies or both, need studies first to determine if vascular or nerve etiology, then typically conservative management (non invasive and electrodiagnostics first)
• Radiation induced brachial plexopathy: when radiation is directed at chest, sensory symptoms with generalized swelling and weakness, most prominent in c5-c6 distribution, should be no venous changes, allen will be normal, no horner
• EMG
• Preganglionic injuries: SNAP normal but clinically insensate, CMAP low or absent
• preganglionic root signifies loss of motor with preservation of sensory conductivity; post ganglionic both sensory and motor
• Postganglionic: SNAP and CMAP low or absent
• Treatment: 
• Free functional muscle transfer provided mainly by the gracillis (obturator nerve). Other options include the latissimus, rectus, and vastus lateralis 

EMG/NCS

• Nerve Conduction: Latency, conduction velocity, amplitude (number of functional axons in the nerve)
• How does it work? (distal to proximal)
• Ring electrodes on finger and wrist electrode (for carpal tunnel)–> latency
• EMG has muscle electrodes that are picked up at a wrist electrode–> amplitude?
• Electrodiagnostic criteria for CTS:
• Distal motor latency >4.5ms (or difference 1ms bt sides)
• Distal sensory latency >3.5ms (or difference between 0.5ms)
• Sensory latencies vulnerable to technical factors
• Cubital tunnel NCV <45-50ms (meters per second) or decrease 15% across the elbow
• Testing across elbow vulnerable to technical factors
• Nerve conduction studies depend on first recorded impulse picked up with large myelinated fibers –> can overlook thinly myelinated smaller fibers (picks up the fastest)
• Amplitude –> number of functioning nerve fibers
• Will show later with motor end plate loss (# recruited)
• Caveats:
• Carpal tunnel –> focal demyelinating, late axon loss
• Conduction velocity latency can be normal in early stages (largest myelinated nerve fibers)
• Advanced can have decreased # or amplitude of nerve fibers 
• Cubital tunnel –> focal demyelinating and axon loss
• Guyons –> axon loss
• Neuropraxia –> demyelinating conduction block –> should not have any amplitude changes, latencies only
• Axonotmesis –> axon loss –> decrease or loss of amplitude and will effect nerve latencies
• False positives 40% (in patients without symptoms), sensitivity for cubital tunnel ranges from 37-86%
• EMG: needle emg –> proximal to distal
• Resting gives sharp or fibrillation waves
• Strength of contraction depends on pattern (recruitment)
• Rest activity: acute or chronic denervation –> early shows fibrillations and sharp waves; late reveals fasciculations, polyphasic
• Fibrillations: individual muscle fibers deprived of innervation –> spontaneously depolarize, occurs 1.5 to 4 weeks and present for months
• Reflections fiber hypersensitivity to Ach and extrajunctional receptors
• Large polyphasic waves for reinnervation
• Activation phase: (recruitment phase) muAP
• EMG can show where nerve injury is, CMAP (compound muscle action potential) amplitudes can reveal how severe nerve injury is (NCS), any MUAP from EMG can show recovery or not (3 months)

• EMG can help access viability of donor
• CRPS
• Reflex sympathetic dystrophy or complex regional pain syndrome: progressive complex pain syndrome –> swelling stiffness and discoloration of hand (vasomotor instability of sympathetic nervous system), hyperhidrosis, osteoporosis, trophic changes may occur (acute subacute chronic); can occur as soon as 10 days with burning pain

• Diagnosis is helpful with bone scan: type I has no etiology, two has neural causality
• Ascorbic acid or vitamin C has been used prophylactically to treat CRPS
• Stellate ganglion blocks reduce sympathetic tone
• C sensory fibers are responsible fibers in CRPS

Miscellaneous

• Potential complication of dequervian’s repair is injury to superficial radial nerve, repair if possible –> if not transposition into brachioradialis, neurolysis stripping etc
• Post-tourniquet syndrome: edema, stiffness, pallor, weakness without paralysis, subjective numbness

• 2 hours recommended tourniquet time, if longer needed then 5 minutes perfusion for every 30 minutes, wide tourniquets better
• Risks for wrong site surgery from high volume, cases in same day, multiple surgeons, deformities
• Myoelectric prosthesis provide more complex movements than body-powered prosthesis
• In compartment syndrome, the median nerve is affected before the ulnar nerve
• Vibration used as modality to desensitize amputation stump neuromas