PERIPHERAL NERVE INJURIES ALI AL-OMARI, MD ASS. PROFESSOR ORTHOPAEDICS AND SPINE SURGERY FACULTY OF MEDICINE JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY

Structure of a nerve epineural sheath: surrounds peripheral nerve Epineurium surrounds a group of fascicles to form peripheral nerve functions to cushion fascicles against external pressure Perineurium connective tissue covering individual fascicles primary source of tensile strength and elasticity of a peripheral nerve  provides extension of the blood-brain barrier provides a connective tissue sheath around each nerve fascicle

Fascicles a group of axons and surrounding endoneurium Endoneurium fibrous tissue covering axons participates in the formation of Schwann cell tube Myelin made by Schwann cells functions to increase conduction velocity Neuron cell cell body - the metabolic center that makes up < 10% of cell mass axon - primary conducting vehicle dendrites - thin branching processes that receive input from surrounding nerve cells

Nerve fiber types Fiber Type Diameter (uM) Myelination Speed Example A 10-20 heavy fast touch B < 3 moderate medium ANS C < 1.3 none slow pain

Pathology of nerve injuries Mechanisms: Ischaemia: 15 min numbness and tingling 30 min loss of pain 45 min muscle weakness Relief of ischemia intense parasthesia for 5 min “pins and needles” sensation restored within 30 seconds muscle power after 10 mins Stretching: 8% affect microcirculation 15%  disrupt axons Examples: Stingers, suprascapular nerve stretching, peroneal nerve after valgus correction in total knee replacement.

Pathology of nerve injuries 3) Compression/crush: Local deformation local ischemia increase vascular permeability endoneural edema axon compression poor axonal transport and nerve dysfunction. fibroblasts invade if compression persists scar impairs fascicular gliding 30 mmHg parasthesia (increase latencies) 60 mmHg complete conduction block. 4) Laceration: Better than compression injuries Ends retract nerve stop producing neurotransmitters nerve start to product proteins of axon regeneration.

Pathology of nerve injuries Regeneration after transection: From proximal to distal Neural sheet intact or repaired Distal segment undergoes Wallerian degeneration (axoplasm and myelin are degraded distally by phagocytes). Existing Schwann cells proliferate and line up on basement membrane. Lee et al. reviewed peripheral never injury and repair. They commented that Wallerian degeneration is initiated 48 to 96 hours after transection. The Schwann cells then align themselves longitudinally, creating columns of cells called Büngner bands. At the tip of the regenerating axon is the growth cone.  Proximal budding (occurs after 1 month delay) leads to sprouting axons that migrate at 1mm/day to connect to the distal tube.

Pathology of nerve injuries Factors affect recovery: Age (most important) Level of injury (distal vs proximal) 2nd most important. Mechanism of injury (sharp vs crush) Repair timing (time limit for repair 18 months). NOTE: PAIN IS FIRST INDICATOR TO RETURN OF FUNCTION

Radiculopathy Weakness in muscles supplied by the nerve root (myotome) Process affecting the nerve root, most commonly by a herniated disc Weakness in muscles supplied by the nerve root (myotome) Sensory loss in the area of the skin supplied by the nerve root (dermatome)

Mononeuropathy Weakness in muscles supplied by the nerve Dysfunction of a single peripheral nerve Weakness in muscles supplied by the nerve Sensory loss in the area of the skin supplied by the cutaneous branches of the nerve

Polyneuropathy Symetrical dysfunction of peripheral nerves Sensory Motor Metabolic, DM, viral ….

Polyneuritis Multiplex Asymetrical involvement of several peripheral nerves Metabolic, viral…

Plexopathy Trunk lesion Cord lesion Can refer to involvement of the entire plexus, or parts of the plexus Trunk lesion Cord lesion Distribution of weakness and numbness depends upon the part of the plexus affected

Neuroma Sprouting of nerve fibers aimlessly resulting in pain and sensitivity to touch along its distribution

Double-crush phenomenon Blockage of axonal transport at one point makes the entire axon more susceptible to compression elsewhere. Cervical radiculopathy or proximal nerve entrapment may coexist with distal nerve compression in double-crush syndrome. Outcome of surgical decompression may be disappointing unless all points of compression are addressed. Logical to start with less complex distal releases first.

Causes Of Neuropathy Metabolic Toxic Viral Compression trauma

Classifications Seddon classification: Neurapraxia Axonotmesis Mild nerve stretch or contusion Focal conduction block No wallerian degeneration Disruption of myelin sheath Epineurium, perineurium, endoneurium intact Prognosis excellent, recovery expected Axonotmesis Incomplete nerve injury Wallerian degeneration distal to injury Disruption of axons Sequential loss of axon, endoneurium, perineurium (Sunderland class 2, 3, and 4) May develop neuroma-in-continuity Recovery unpredictable  

Neurotmesis Complete nerve injury Focal conduction block Wallerian degeneration distal to injury Disruption of all layers, including epineurium Proximal nerve end forms neuroma Distal end forms glioma Worst prognosis

Classifications Sunderland classification 1st degree 2nd degree same as neurapraxia 2nd degree same as axonotmesis 3rd degree  injury with endoneurial scarring most variable degree of ultimate recovery 4th degree nerve in continuity but at the level of injury there is complete scarring across the nerve) 5th degree same as neurotmesis

Classifications

Classifications

Clinical features Nerve injuries are easily missed if associated with fractures and dislocations. Always test for nerve injuries in any significant trauma, pre- and post- operation or manipulation. Full neurological exam (abnormal gaits, weakness in specific muscle group, change in sensibility) If nerve injuries is diagnosed look for accompanying vascular injuries. OPEN WOUND  EARLY EXPLORATION.

Clinical features Tinel’s sign: Level, type and degree of damage. Low energy neurapraxia High energy axonotmesis or neurotmesis. In doubtful case, wait and see to role out complete transection. Time of recovery!!! Tinel’s sign: Peripheral tingling provoked by percussion the nerve at site of injury. Sensitive spot progress distally in regenerating nerve.

Clinical features Electrodiagnostic tests: EMG (Electromyography) NCV (LATANCIES MORE IMPORTANT THAN VELOSITY)

Principles of Localization Certain sites are prone to nerve entrapments/injuries Nerve opposing bone Ulnar nerve at the elbow Closed spaces Carpal tunnel Adjacent structures Median nerve at the elbow, adjacent to the brachial artery

Principles of localization, cont Order in which branches arise Movements at specific joints Single nerve Elbow extension Radial Multiple nerves Elbow flexion Musculocutaneous

Typical deformities : Wrist drop ---- radial nerve injury Claw hand ---- ulnar nerve injury Foot drop ---- common peroneal nerve injury Ape thumb ---- median nerve injury Winging of scapula ---- long thoracic nerve injury Pointing index ---- median nerve injury

Factors Affecting Recovery In favor Younger age Type of injury More distal injury Time of repair: first 3 weeks Pure motor or sensory

Treatment Nonoperative Operative observation with sequential EMG indications neuropraxia (1st degree) axonotmesis (2nd degree) Operative surgical repair neurotomesis (3rd degree)

Treatment Open wound early exploration and primary repair with 10-0 epineural repair, if large defect more than 2.5 cm despite of mobilization autograft (sural, saphenous, lateral antebrachial, etc) vs allograft (collagen conduits) physiotherapy. Close wound  wait and see failure of recovery within time frame (good care for paralyzed part and dynamic splint) delayed repair with resection of proximal neuroma and distal glioma.

Treatment Direct muscular neurotization Epineural Repair insert proximal nerve stump into affected muscle belly results in less than normal function but is indicated in certain cases Epineural Repair primary repair of the epineurium in a tension free fashion first resect proximal neuroma and distal glioma it is critical to properly align nerve ends during repair to maximize potential of recovery

Treatment Fasicular repair indications three indications exist for grouped fascicular repair median nerve in distal third of forearm ulnar nerve in distal third of forearm sciatic nerve in thigh technique similar to epineural repair, but in addition repair the perineural sheaths (individual fascicles are approximated under a microscope) outcomes no improved results have been demonstrated over epineural repair Nerve grafting autologous graft remains the gold standard of repair for segmental defects > 5cm is autologous nerve grafting  allograft the only synthetic graft which shows equal results to autologous nerve grafting is a collagen conduit collagen conduits allow for nutrient exchange and accessibility of neurotrophic factors to the axonal growth zone during regeneration

COMPRESSION NEUROPATHies OF THE UPPER LIMB

Entrapment neuropathy is caused by the direct pressure on a single nerve. Symptoms & signs depend on which nerve is affected. Earliest symptoms to occur: tingling & neuropathic pain. Followed by reduced sensation or complete numbness Muscle weakness is noticed later, followed by muscle atrophy.

Pathophysiology COMPRESSION VENOUS OBSTRUCTION + ISCHEMIA ANOXIC SEGMENT NEURAL EDEMA & DILATATION OF SMALL VESSELS EXACERBATION OF ORIGINAL COMPRESSION CONT OF VICIOUS CYCLE PERSISTENT EDEMA + ANOXIA/ HYPOXIA FIBROSIS IMPAIRMENT OF SUPPLY DEFICIENCY OF VITAL NUTRIENTS FUNCTIONAL IMPAIRMENT PERMANENT IMPAIRMENT OF FUNCTION IF LEFT UNTREATED

MEDIAN NERVE CARPAL TUNNEL SYNDROME ANTERIOR INTEROSSEOUS SYNDROME 3 important compression neuropathies from distal to proximal CARPAL TUNNEL SYNDROME ANTERIOR INTEROSSEOUS SYNDROME PRONATOR SYNDROME

CARPAL TUNNEL SYNDROME Results from compression of the median nerve within the carpal tunnel. Most common compression neuropathy in the upper limb. ANATOMY - Cylindrical cavity connecting the volar forearm with the palm. - Floor: transverse arch of carpal bones - Medially: hook of hamate, triquetrum & pisiform - Laterally: scaphoid, trapezium & fibro osseous flexor carpi radialis sheath. - Roof: proximally flexor retinaculum, transverse carpal ligament over the wrist and aponeurosis between thenar & hypothenar muscles distally.

CONTENTS: Tendons of flexor digitorum superficialis & profundus in a common sheath Tendon of flexor pollicus longus in an independent sheath Median nerve

ETIOLOGY: DECREASE IN SIZE OF CARPAL TUNNEL Bony abnormalities of the carpal bones Acromegaly INCREASE IN CONTENTS OF CANAL Forearm & wrist fractures (colle’s, scaphoid) Dislocations & subluxations (scaphoid rotary subluxation, lunate volar dislocation) Post traumatic arthritis (osteophytes) Aberrant muscles (lumbricals, palmaris longus, palmaris profundus) Local tumours (neuroma, lipoma, ganglion, cysts, multiple myeloma) Persistent medial artery Hyrertrophic synovium Hematoma (hemophilia, anti coagulation therapy, trauma)

EXTERNAL FORCES DM Alcoholism Double crush syndrome NEUROPATHIC CONDITIONS DM Alcoholism Double crush syndrome Exposure to industrial solvents INFLAMMATORY CONDITIONS Rheumatoid arthritis Gout Non specific tenosynovitis Infections EXTERNAL FORCES Vibration Direct pressure

Thyroid disorders (esp. hypothyroidism) Renal failure ALTERATIONS OF FLUID BALANCE Pregnancy Menopause Eclampsia Thyroid disorders (esp. hypothyroidism) Renal failure Long term hemodialysis Raynaud’s disease Obesity

Clinical Features Paresthesias and pain (often at night) in volar aspect of radial 3½ digits (thumb, index, long and radial half of ring) Large sensory fibers (light touch, vibration) are affected before small fibers (pain and temperature) Pain usually wake up patient from sleep Weakness, loss of fine motor control, and abnormal two- point discriminationare later findings. Thenar atrophy may be present in severe denervation

CLINICAL FEATURES: SIGNS : Tinel's sign, thenar atrophy, sensory changes in the distribution of median nerve Tinel’s sign: percussing the median nerve at the wrist. Phalen’s test: Patient places elbow on table, forearm vertical with wrist flexed. Numbness & Tingling in median nerve distribution occurs in 60 seconds in + ve cases. Reverse Phalen’s test: Sustained extension of the wrist may also aggravate the symptoms. Not a reliable test.

TOURNIQUET TEST: Inflating a BP cuff on the arm to a pressure above systolic pressure will initiate symptoms (paraesthesia & numbness). DURKAN’S TEST: Application of direct pressure on the carpal tunnel with either pressure manometer or by thumb of the examiner for 30 seconds will produce the symptoms. SENSORY TESTS Weber’s 2 point discrimination test: Test is positive in about one-third cases. Semmes - Weinstein monofilaments: Monofilaments of increasing diameters are touched to palmar side of the digit until the patient can tell which digit is touched.

INVESTIGATIONS: Electro diagnostic studies: Most reliable confirmatory test. Conduction time & latency for both sensory & motor conduction is determined. CT & MRI: If mass is suspected within the carpal tunnel LABORATORY TESTS: specific cause is suspected Renal & thyroid function, RA factor, ESR, Anti nuclear antibody, uric acid, blood sugars. Radiographs: Wrist AP, Lateral, Carpal tunnel views. Useful in detecting congenital anomalies, fractures, Calcific deposits or tumours of carpal bones. TREATMENT: NON OPERATIVE OPERATIVE

NON OPERATIVE: OPERATIVE: Activity modification NSAID’S Splinting Treating the underlying disease Local steroid injections OPERATIVE: OPEN CARPAL TUNNEL RELEASE ENDOSCOPIC CARPAL TUNNEL RELEASE

OPEN CARPAL TUNNEL RELEASE: Incision & deeper dissection are performed ulnar to the longitudinal plane between the ulnar border of the ring finger & a point along the wrist crease noted by flexing the ring finger against the palm. Transverse carpal ligament is divided proximally to distally.

COMPLICATIONS: Incomplete division of transverse carpal ligament. Division of palmar cutaneous branch or motor branch of median nerve. Injury to superficial palmar vascular arch. Reflex sympathetic dystrophy. Palmar hematoma Loss of grip strength.

Co existent ulnar tunnel release. Limited wrist & finger extension. ENDOSCOPIC CARPAL TUNNEL RELEASE Emerging technology for open decompression of the carpal tunnel. CONTRAINDICATIONS: Co existent ulnar tunnel release. Limited wrist & finger extension. Tenosynovitis Previous surgery

ANTERIOR INTEROSSEOUS SYNDROME Anterior interosseous branch of the median nerve supplies the flexor digitorum profundus to the index finger, flexor pollicis longus & pronator quadratus. Provides sensation to the volar aspect of carpus. POTENTIAL SITES OF COMPRESSION: Fibrous bands of the flexor digitorum superficialis Fibrous bands of the deep or superficial heads of the pronator teres. LESS COMMMON CAUSES Anomalous muscles Enlarged / thrombosed vessels Tumours Enlarged bursae

Weakness of flexion in the IP joint of the thumb. CLINICAL FEATURES: Weakness of flexion in the IP joint of the thumb. Weakness of flexion in the DIP joint of index finger. No sensory loss Pain is exacerbated by exercise & relieved by rest. Number of cases occur due to a viral neuropathy. TREATMENT INITIALLY: CONSERVATIVE SURGICAL: INDICATIONS No resolution of symptoms Severe symptoms SURGICAL EXPLORATION: Identification & division of the offending structure.

PRONATOR SYNDROME Below lacertus fibrosus Anatomical sites of compression: Below lacertus fibrosus Between the 2 heads of pronator teres

Numbness in the distribution of the median nerve. CLINICAL FEATURES Ache or discomfort in the forearm associated with weakness or clumsiness of the hand. Numbness in the distribution of the median nerve. Night pain is not common. Phalen’s test & Tinel's sign: negative Difficult to demonstrate electrophysiological abnormality.

Possible sites checked Appropriate release is done. TREATMENT CONSERVATIVE: NSAID’S Splinting with the elbow at 90 degrees, slight forearm pronation & wrist flexion. SURGICAL: Exploration of distal 5 to 8 cm of the course of the median nerve in the arm combined with its course in the upper forearm. Possible sites checked Appropriate release is done.

ULNAR NERVE At the elbow (cubital tunnel syndrome) Ulnar nerve gets entrapped at 2 common sites: At the elbow (cubital tunnel syndrome) Guyon’s canal (ulnar tunnel syndrome)

CUBITAL TUNNEL SYNDROME Second commonest nerve entrapment of the upper limb ANATOMY: CUBITAL TUNNEL Starts at the groove between the olecranon & the medial epicondyle. Tunnel is formed by a fibrous arch connecting the 2 heads of the flexor carpi ulnaris & lies just distal to the medial epicondyle.

Tight fascial band over the cubital tunnel. Medial head of triceps CAUSES OF ENTRAPMENT ARCADE OF STRUTHER’S: Formed by superficial muscle fibres of the medial head of triceps attaching to the medial epicondyle ridge by a thickened condensation of fascia. Tight fascial band over the cubital tunnel. Medial head of triceps Aponeurosis of flexor carpi ulnaris Recurrent subluxation of ulnar nerve, results in neuritis. Osteophytic spurs Cubitus valgus following supra condylar fracture.

Hand weakness & clumsiness CLINICAL FEATURES Numbness involving the little finger & the ulnar half of the ring finger. Hand weakness & clumsiness Tenderness over the ulnar nerve at the elbow. Tinel’s sign is positive: exacerbation of paraesthesia’s with light percussion over the ulnar nerve. Advanced cases : clawing of the ring & little fingers

TREATMENT NON OPERATIVE: Early stages Activity modification Immobilization of the elbow in 30 degrees of extension, followed by periods of mobilization with elbow padding. SURGICAL: Decompression of the nerve by dividing of the basic offending structure. Anterior transposition of the ulnar nerve Medial epicondylectomy

ULNAR TUNNEL SYNDROME Ulnar nerve is compressed as it passes through GUYON’S canal in the wrist. Less common than entrapment of the ulnar nerve at the elbow.

Medial wall : pisiform & pisiohamate ligament. ANATOMY: GUYON’S CANAL ROOF: composed of palmar carpal ligament blending into the FCU tendon attaching to the pisiform & the pisiohamate ligaments. Medial wall : pisiform & pisiohamate ligament. Lateral wall: hook of hamate & some fibres of the transverse carpal ligament. Ulnar nerve enters guyon’s canal accompanied by ulnar A & Ulnar V. Guyon’s canal lies in the space between flexor retinaculum & volar carpal ligaments.

The anatomy of distal ulnar tunnel is divided into 3 zones. Zone 1:proximal to the bifurcation of the ulnar nerve & consists of both sensory & motor fibres of the nerve. Zone 2: represents the motor branch of the ulnar N distal to the bifurcation. Zone 3: represents the sensory branches of the ulnar nerve beyond its bifurcation.

Clinical presentations: ZONE 1 LESIONS : Mixed sensory & motor loss. ZONE 2 LESIONS : Isolated motor deficit. ZONE 3 LESIONS : Isolated ulnar N sensory loss. Common Causes in zone 1 & 2: ganglions, fractures of the hook of hamate. Zone 3: ulnar artery thrombosis OTHER CAUSES: Malunited fracture of fourth/fifth metacarpal. Anomalous muscles Occupational trauma

INVESTIGATIONS X RAY : Oblique/carpal tunnel views Delineate bony anatomy to diagnose hook of hamate fractures. MRI: Ganglia, space occupying lesions TREATMENT Operative release of the canal by reflecting the FCU, pisiform & pisiohamate ligament ulnarly. Distal deep fascia of the forearm below the wrist crease should be released. Resection of any space occupying lesion Treatment of hook of hamate fractures.

RADIAL NERVE PROPER RADIAL NERVE PALSY “SATURDAY NIGHT PALSY” POSTERIOR INTEROSSEOUS NERVE SYNDROME RADIAL TUNNEL SYNDROME WARTENBERG’S SYNDROME

Proper radial nerve Rarely compressed by lateral head of triceps, typically compromised in setting of humerus trauma or related surgical approaches “Saturday night palsy”—Intoxicated patient passes out with arm hanging over chair, wakes up with wrist drop. Clinical findings include weakness of proper radial nerve–innervated muscles such as triceps, brachioradialis, and ECRL plus muscles innervated by the PIN. Sensory deficits may be present in distribution of superficial sensory branch. EMG may be helpful. May be initially observed but may be explored if no significant recovery after 3 months

Posterior interosseous nerve compression syndrome PIN is a branch of the radial nerve that provides motor innervation to the extensor compartment Symptoms include lateral elbow pain and distal muscle weakness. Radial deviation with active wrist extension because ECRL innervated by proper radial nerve more proximally. PIN innervates the ECRB, supinator, EIP, ECU, extensor digitorum communis (EDC), extensor digiti minimi, APL, EPB, and EPL. Patients may also have dorsal wrist pain, where the terminal nerve fibers provide sensory innervation to the dorsal wrist capsule. Terminal branch is located on the floor of the fourth extensor compartment. EMG may be helpful.

Anatomic sites of compression include Fascial band at the radial head Recurrent leash of Henry Edge of the ECRB Arcade of Frohse (the most common site, proximal edge of the supinator) Distal edge of the supinator

Unusual causes include chronic radial head dislocation, Monteggia fracture- dislocation, radiocapitellar rheumatoid synovitis, and space-occupying elbow mass (e.g., lipoma) PIN palsy is differentiated from extensor tendon rupture by a normal wrist tenodesis test. Nonoperative treatment includes activity modification, splinting, and NSAIDs. Operative intervention warranted if no recovery by 3 months Surgical decompression of anatomic sites of compression provides good to excellent results for 85% of patients.

RADIAL TUNNEL SYNDROME Characterized by lateral elbow and radial forearm pain without motor or sensory dysfunction Provocative tests include resisted long-finger extension (positive if resistance reproduces pain at the radial tunnel) and resisted supination Lateral epicondylitis coexists in a small percentage of patients. The point of maximum point tenderness is anterior and distal to the lateral epicondyle.

Despite affecting the same nerve (PIN) and sites of compression,electrodiagnostic tests are typically normal. Prolonged nonoperative treatment for up to 1 year with activity modification, splints, NSAIDs, and local modalities. Success of surgical decompression less predictable than for PIN syndrome, with good to excellent results in only 50% to 80% after prolonged postoperativerecovery

Wartenberg syndrome Compressive neuropathy of superficial sensory branch of the radial nerve Compressed between brachioradialis and ECRL with forearm pronation (by a scissor-like action between the tendons) Symptoms include pain, numbness, and paresthesias over the dorsoradial hand. Provocative tests include forceful forearm pronation for 60 seconds and a Tinel sign over the nerve. Initially treated by activity modification, splinting, and NSAIDs Surgical decompression warranted if 6-month trial of nonoperative treatment fails.

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