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Hand II: Nerve Entrapment Nadia Afridi MD, BSc (Med) Justin Paletz MD, FRCSC Basic Nerve Facts Anatomy – Endoneurium • Surrounds axons of peripheral nerves – Fascicles • Groups of axons – Perineurium • Surrounds individual fascicles – Epineurium • Intraneural • Outer circumferential Basic Nerve Facts Anatomy – Epineurium • Intraneural • Outer circumferential Basic Nerve Facts Anatomy – Epineurial repair • Outer epineurium sutured – Fascicular bundle and perineurial repair • Inner epineurium repaired – Fascicular repair • Perineurium sutured Basic Nerve Facts Anatomy – Vascular supply • Arteriae nervorum – Enter nerve segmentally – Divide into longitudinal superficial and interfascicular arterioles – Longitudinal epineurial and perineurial vessels • ALLOW FOR INTRANEURAL DISSECTION FOR FASCICULAR REPAIR – Internal neural anatomy • Discrete bundles and branches Basic Nerve Facts Physiology – Peripheral nerve signaling • Localized potentials – Short distances – Decrease over distance – Key for intercellular junctions and sensory nerve endings • Action potentials – Conducted impulses that DO NOT decrease over distance Basic Nerve Facts Physiology – Peripheral nerve signaling • Action potentials – Unmyelinated fibers • Rate of conduction directly proportional to cross section of axon – Myelinated fibers • Impulse jumps from each site of interrupted myelin sheath (Node of Ranvier) • SALTATORY CONDUCTION Basic Nerve Facts Physiology – Peripheral nerve transport mechanism • Nutrient production • Axoplasmic transport systems • Breakdown products – retrograde axoplasmic transport • Disruption of transport systems Basic Nerve Facts Nerve injury – Two classification systems • Seddon – Neuropraxia, axonotomesis, neurotmesis – Based on clinical evaluation and judgment of injury – Preoperative assessment • Sunderland – 1st to 5th degree – Histology – Applicable after nerve exploration Basic Nerve Facts Nerve repair – Timing • Functional results of primary and early secondary nerve repair similar • Primary best: – – – – – – Proximal injuries Identifiable nerve ends Minimal contamination Without associated injuries Healthy patient Trained surgeon • Delayed primary repair within 7 days Basic Nerve Facts Nerve repair – Timing • Secondary repair – After 7 days – Nerve stumps approximated and tagged – Repair within 6 months • Better result than after 6 months • Optimal timing of repair – Controversial • Immediate • 3 weeks - fibrosis ideal for repair? Basic Nerve Facts Nerve repair – Patient age • Younger patient – Better functional outcome – Optimal recovery in less than 20 years of age • Motor/sensory nerve – Digital nerve repairs • Good results up to 50 years of age – Condition of the wound • Increased intraneural damage with extensive injuries Basic Nerve Facts Nerve repair – Level of Injury • More proximal injury – Worse functional return – Tension of repair • Elasticity of neural tissues • Elongation by 20% – After this point nerve conductivity diminishes – Gap size • Worse results with gap > 2.5 cm • Bridge with grafting, neurotization Basic Nerve Facts Nerve repair – Technique • Alignment • Precise match of motor and sensory fascicles • No significant difference in outcome by type of repair – Epineurial – Perineurial – Group Fascicular Basic Nerve Facts Nerve repair – Technique • Epineurial – Conventional technique – Aligned with two or three sutures – Advantages: • Short execution time • Technical ease • Minimal magnification • Intraneural contents undisrupted – Disadvantages • Imprecise alignment • Performance by poorly trained personnel Basic Nerve Facts Nerve repair – Technique • Perineurial (Fascicular or Funicular) – Technique of choice in nerve grafting – Best in nerves with fewer than 5 fascicles – Advantages: • Better fascicular alignment • More axons entering endoneurial tubes – Disadvantages: • Longer operative time • Increased fibrosis at suture site • Vascular compromise of fasciculi • Trauma to nerve Basic Nerve Facts Nerve repair – Technique • Group fascicular repair – Possible when nerve transection at level of distinct functional groupings – Motor-motor, sensory-sensory Basic Nerve Facts Nerve repair – Nerve grafting • Recommended for gaps > 2 cm • Interfascicular technique • Best recovery if grafting performed between 6-12 months postinjury • Sural nerve most common donor • Multiple other described techniques: – Vascularized nerve – Various donors Nerve Entrapment Epidemiology – Increasing rate of CTS – Risk factor: • • • • Female gender Pregnancy Diabetes Rheumatoid arthritis – Small carpal tunnel area not a risk factor – No universal acceptance of job related issues Nerve Entrapment Pathophysiology – Systemic conditions • • • • • Diabetes Alcoholism Hypothyroidism Exposure to industrial solvents Aging – Depression of nerve function – Lowers threshold for manifestation of compression neuropathy Nerve Entrapment Pathophysiology – Ischemia/Mechanical Factors • Earliest manifestation – Reduced epineurial blood flow – 20-30 mmHg compression • Interference in venular flow – 40-50 mmHg • Impairment of arteriolar and interfascicular capillary flow – 60-80 mmHg • Complete blockage of nerve perfusion Nerve Entrapment Pathophysiology – Double crush phenomenon • Axoplasmic transport systems disrupted – Mechanical – Diabetes etc… • “A nerve with a conduction disorder at one level is more vulnerable to a conduction disorder at a second level” Nerve Entrapment Diagnosis – History • • • • • • Patient’s description Duration and rate of progression Accurate localization of sensory loss Functional loss? Positional or nocturnal variance? Ask about legal involvement (USA) Nerve Entrapment Diagnosis – Physical • Brief limb survey • Screening sensation test – Light touch of affected area compared to known normal • Two point discrimination – Can remain normal if minimal number of fibers functioning normally Nerve Entrapment Diagnosis – Sensory testing • Semmes Weinstein – Slowly adapting fibers – Simple and inexpensive • Vibration test • Both most sensitive to progressive changes in nerve function Nerve Entrapment Diagnosis – Electrodiagnostic studies • Diagnostic gold standard • Can aid in confirming diagnosis in some cases • Fallible to user error and sensitivity of equipment Nerve Entrapment Diagnosis – Radiographic examination • Occasionally useful • Rule out neck pathology in diffuse presentation • Cxray – Pancoast tumor • MRI – Best study for showing nerve compression at brachial plexus down to carpal tunnel Median nerve Anatomy – Derived from C5-T1 – Runs medial to axillary and brachial arteries – Passes deep to bicipital aponeurosis and flexor muscle mass – 80% passes between two heads of pronator teres – Continues between FDS and FDP – Emerges in forearm radial to superficialis tendons – Passes under transverse carpal ligament Median nerve Anatomy – Superficial trunk supplies: • • • • Pronator teres FCR PL FDS index – Deep trunk supplies (anterior interosseus nerve): • • • • FDP to index and middle FPL Pronator quadratus Sensation to radial carpal joint Median nerve Anatomy – 5-6 cm proximal to anterior wrist crease • Palmar cutaneous branch – Innervates skin at base of palm – Does not pass through carpal tunnel – Beneath transverse carpal ligament • Recurrent motor branch – Supplies thenar muscles, 1st and 2nd lumbricals • Three proper digital nerves and two common digital nerves Median nerve Anatomy – Martin-Gruber anastomosis • Motor connnection median and ulnar nerve proximal forearm • Between anterior interosseus nerve and ulnar nerve more distally – Riche-Cannieu anastomoses • Motor connection between median and ulnar motor branches in the palm Median nerve Anatomy – Carpal tunnel • Boundaries – Roof (Volar): • Transverse carpal ligament – Floor (Dorsal): • Volar ligaments and carpal bones – Lateral wall (Radial): • Scaphoid tuberosity and trapezial crest – Medial wall (Ulnar): • Pisiform and hook of the hamate Median nerve - Entrapment Carpal Tunnel Syndrome • Pain and paresthesias palmar radial hand – – – – – Worse at night Driving Exacerbated with repetitive forceful use Sensation of swelling Normal sensation in area of palmar cutaneous branch of median nerve • Motor function – Late sign • Clumsiness • Thenar atrophy • Weak thumb abduction Median nerve - Entrapment Carpal Tunnel Syndrome – Provocative tests • Tinel’s sign – Production of paresthesias with percussion at the carpal tunnel entrance • Compression test • Phalen’s test – Symptoms with wrist flexion • Reverse Phalen’s test • Tourniquet test – Above systolic pressure Median nerve - Entrapment Carpal Tunnel Syndrome – Sensory testing – early • Semmes-Weinstein monofilament • Vibrometry – Late • Two point discrimination Median nerve - Entrapment Carpal Tunnel Syndrome – Electrodiagnostic studies • Sensory and motor – False negative as high as 10-20% • Diagnostic criteria – Distal motor latency >4.5 ms – Distal sensory latency >3.5 ms – Asymmetry between hands • Motor > 1 ms, Sensory > 0.5 • Comparison to ulnar nerve – >0.8 ms difference Median nerve - Entrapment Carpal Tunnel Syndrome – Treatment • Conservative – – – – Attempt in mild disease with intermittent paresthesias Splinting to prevent wrist flexion Systemic anti-inflammatory medications Steroid injection • Controversial • Transient relief in 80% • 22% symptom free after 12 months – Ergonomic adjustments – Failure to respond • Surgical decompression Median nerve - Entrapment Carpal Tunnel Syndrome – Surgical technique • Open – Variety of skin incisions – Incision between 3rd and 4th metacarpals – Caution re: palmar cutaneous branch and recurrent motor branch – Through palmar fascia – Transection of transverse carpal ligament • Endoscopic – Controversial Median nerve - Entrapment Carpal Tunnel Syndrome – Outcomes • 80% patients experience excellent or good results • 10-15% fair results • 5-10% poor results • Pain relief IMMEDIATE • Maximum recovery 6-12 months after surgery – Numbness – Weakness Median nerve - Entrapment Pronator syndrome – Presentation: • • • • Distal arm and proximal forearm pain Pain increases with activity Paresthesias in median nerve distribution Tinel’s sign – Positive over nerve • Symptoms increased by resisted forceful pronation with elbow extended Median nerve - Entrapment Pronator syndrome – Four sites median compression at elbow: • Ligament of Struthers – Supracondylar process of humerus to superficial head of pronator • Lacertus fibrosus – Biceps • Pronator teres • FDS fibrous arch of origin Median nerve - Entrapment Pronator syndrome – Provocative tests • Ligament of Struthers – Elbow flexion • Lacertus fibrosus – Resisted elbow flexion • Pronator teres – Resisted pronation with the elbow extended and digits relaxed • FDS fibrous arch – Median symptoms with resisted FDS of the long finger Median nerve - Entrapment Pronator syndrome – Electrodiagnostic studies • Nerve conduction and EMG not helpful – 50% of diagnoses can be confirmed with EMG • Serial clinical exams more useful – Persistent pain and physical findings – Normal electrodiagnostic studies – Diagnosis still relevant Median nerve - Entrapment Pronator syndrome – Treatment • Conservative – Same • Operative – Above elbow flexion crease to distal forearm – Examine and release all four sites of possible entrapment Median nerve - Entrapment Pronator syndrome – Outcomes • Almost successful as wrist median decompression • 60-70% patients experience improvement Median nerve - Entrapment Anterior interosseus syndrome – Presentation • • • • • Vague deep forearm pain Aggravated by activity Relieved by rest No sensory disturbance Weakness of index FDP, FPL – Characteristic posture • Unable to form “6” with fingers Median nerve - Entrapment Anterior interosseus syndrome – Provocative tests • Test pronator quadratus – Resisted forced supination with elbow maximally flexed – Eliminated effect of humeral pronator teres • Pain elicited with resisted flexion long FDS – Site of compression • Fibrous bands in pronator teres Median nerve - Entrapment Anterior interosseus syndrome – Electrodiagnostic studies • Useful in this neuropathy • Electromyographic evaluation – Index FDP – FPL – Pronator quadratus Median nerve - Entrapment Anterior interosseus syndrome – Treatment • Conservative – Splinting – Observation – NSAIDS • Surgical – Confirmation of diagnosis – Failure of spontaneous improvement in 2 months Ulnar nerve Anatomy – Continuation of medial cord of brachial plexus • C8 and T1 – Axilla • Lies deep to pectoralis minor • Between axillary artery and vein – Descends in arm medial to brachial artery between coracobrachialis and triceps Ulnar nerve Anatomy – Passes through medial intermuscular septum – Lies in groove at medial head of triceps – Fascial arch • Arcade of Struthers – Lies across nerve 70% patients – 7-10 cm proximal to medial epicondyle – Passes posterior to medial epicondyle – Cubital tunnel – Passes between humeral and ulnar heads of FCU Ulnar nerve Anatomy – Small branches to elbow joint – Innervates proximal FCU – Dorsal sensory branch • 4-6 cm proximal to wrist • Outside of Guyon’s canal – Nerve of Henle • Ulnar artery Ulnar nerve Anatomy – Guyon’s canal • Triangular • Roof – Superficial volar carpal ligament • Medial – Pisiform • Lateral – Hook of the hamate Ulnar nerve Anatomy – Hand • Deep (motor) branch – – – – – – Hypothenar eminence Midpalm Interossei Two ulnar lumbricals Adductor pollicis Deep head of FPB • Superficial (sensory) branch – Radial carpal joint – Ulnar aspect hand • Palmar cutaneous branch of ulnar nerve absent when nerve of Henle present Ulnar nerve - Entrapment Ulnar tunnel syndrome – Presentation: • Rare • Entrapment of ulnar nerve in Guyon’s canal – Numbness in ulnar two digits – Sensation in dorsal sensory branch spared • Pure motor, sensory or mixed • Etiologic factors – Use of “heel of hand” – Space occupying lesions • Ganglia, bony, pseudoaneurysms Ulnar nerve - Entrapment Ulnar tunnel syndrome – Presentation: • Pain in wrist – Numbness – Tingling – Burning – Provocative tests • Sustained hyperextension or flexion of wrist Ulnar nerve - Entrapment Ulnar tunnel syndrome – Physical • Intrinsic weakness • Sensory testing • Allen test – Dopplers • Fractures of hook of hamate – Electrodiagnostic studies • Establish diagnosis Ulnar nerve - Entrapment Ulnar tunnel syndrome – Treatment • Conservative – Splint – NSAIDs • Surgical – Refractory to conservative care – Documented anatomic lesions – Release Guyon’s canal Ulnar nerve - Entrapment Cubital tunnel syndrome – “Tardy ulnar palsy” – Presentation: • • • • • 2nd most common site Repetitive elbow flexion-extension Elbow pain Sensory disturbance in ulnar nerve distribution Weakness of ulnar intrinsics – 1st dorsal interosseus – Adductor pollicis – Key pinch strength • Interosseus wasting Ulnar nerve - Entrapment Cubital tunnel syndrome – Physical • • • • • • • Tinel’s at medial epicondyle Subluxation of nerve Snapping of triceps Decreased pinch strength Intrinsic atrophy Weakness in small FDP and FCU “wish sign” – Crossing middle over index Ulnar nerve - Entrapment Cubital tunnel syndrome – Wartenberg’s sign • Abducted habitus of small finger • Weak adduction by third palmar interosseus – Froment’s sign • Compensatory hyperflexion of thumb IP • Hyperextension thumb MP secondary to loss of adductor pollicis and FPB (deep head) – Claw hand • MP hyperextension Ulnar nerve - Entrapment Cubital tunnel syndrome – Provocative tests • Elbow flexion test – Increase in cubital tunnel pressure with flexion – Aggravates symptoms Ulnar nerve - Entrapment Cubital tunnel syndrome – Electrodiagnostic studies • Can confirm cubital tunnel • Conduction velocities useful – Vary with elbow position – Three segments: • Above elbow • Across elbow • Forearm – Dip in CV across elbow with forearm recovery significant (>20%) Ulnar nerve - Entrapment Cubital tunnel syndrome – Treatment • Conservative management – – – – Splint NSAIDs Avoidance of elbow trauma Inappropriate to attempt if: • MUSCLE ATROPHY, WEAKNESS OR PERMANENT SENSORY CHANGES Ulnar nerve - Entrapment Cubital tunnel syndrome – Treatment • Surgical – Four approaches: 1. Simple decompression – fascial covering split 2. Medial humeral epicondylectomy 3. Anterior subcutaneous transposition 4. Anterior submuscular transposition – Latter two approaches most commonly used Ulnar nerve - Entrapment Cubital tunnel syndrome – Treatment • Surgical – Keypoints: • Protect medial antebrachial cutaneous nerve of forearm and its branches • Release Arcade of Struthers and Osborne’s ligament • Split FCU but protect motor nerve • Excise band between medial epicondyle and shaft of humerus • Hemostasis Ulnar nerve - Entrapment Cubital tunnel syndrome – Treatment • Surgical – Technique • Incision midway between olecranon and medial epicondyle • 8 cm proximal and 6 cm distal • Identification proximally and distal dissection • Cubital tunnel release • Protect articular sensory and FCU branches • Release of intermuscular septum Ulnar nerve - Entrapment Cubital tunnel syndrome – Outcomes • Minimal compression – Excellent results in 90% • Moderate compression – Excellent in 50% Radial nerve Anatomy – Arises from C5-T1 (posterior cord) – Descends around humerus in spiral radial groove beneath lateral head of triceps – Emerges through lateral intermuscular septum • 10-15 cm proximal to lateral epicondyle Radial nerve Anatomy – Travels: • Medial – between brachialis and biceps tendon • Lateral – brachioradialis and ECRL, ECRB – Supplies: • brachioradialis, ECRL, ECRB Radial nerve Anatomy – Divides at elbow into: • Superficial sensory division – Travels under brachioradialis – Emerges at midforearm subcutaneously • Deep motor branch – Posterior interosseus nerve – Passes deep under fibrous proximal margin of supinator • Arcade of Froshe – Innervation to extensors, sensory to wrist Radial nerve - Entrapment Radial tunnel syndrome – Presentation • Pain localized to tender extensor muscle mass • Radiates to wrist and dorsum hand • Worse with use of arm • Heaviness and fatigability • Often misdiagnosed as lateral epicondylitis • Involves both divisions of radial nerve – Weakness with digital extension Radial nerve - Entrapment Radial tunnel syndrome – Physical examination • Tenderness over “mobile wad” – Brachioradialis and radial wrist extensors – Provocative tests • Firm pressure over radial nerve at supinator muscle • Third finger test – Increased pain with resisted extension of long finger with elbow extended • Resisted supination Radial nerve - Entrapment Radial tunnel syndrome – Electrodiagnostic studies • Usually normal Radial nerve - Entrapment Radial tunnel syndrome – Treatment • Conservative – Rest from repetitive motions – Splints – Concurrent lateral epicondylitis • Steroid injection – Spontaneous remission can occur in mild cases Radial nerve - Entrapment Radial tunnel syndrome – Treatment • Surgical – Indicated in failed conservative treatment – CRITICAL release of: • Arcade of Froshe • Vascular leash of Henry Radial nerve - Entrapment Posterior interosseus compression – Presentation • Aching pain – Similar to radial tunnel syndrome • Weakness of digital extensors • No sensory disturbance – Physical • Weakness of ECU, thumb and finger extensor, APL Radial nerve - Entrapment Posterior interosseus compression – Electrodiagnostic studies • Can be confirmatory Radial nerve - Entrapment Posterior interosseus compression – Treatment • Conservative – Splinting – Systemic steroids (short course) • Surgical – Indicated if no recovery after 3 months of conservative treatment Radial nerve - Entrapment Wartenberg’s syndrome – Presentation • Involvement of superficial sensory branch of radial nerve – Dorsoradial aspect of the hand • Emerges between brachioradialis and ECRL – Compressed by scissor like action with pronation • Complaints of pain and paresthesias with forearm pronated • Differentiate – deQuervain’s tenosynovitis Radial nerve - Entrapment Wartenberg’s syndrome – Provocative tests • Forceful pronation of forearm against resistance – 30-60 seconds – Tightens brachioradialis across the nerve – Diagnosis • Electrodiagnostic studies • Local anaesthetic block Radial nerve - Entrapment Wartenberg’s syndrome – Treatment • Conservative – – – – Splinting NSAIDs Local steroid injection Changes in work activities • Surgical – Failed conservative treatment – Release fascia of brachioradialis and ECRL