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COMPRESSION NEUROPATHIES

Nerve compression overview

  • Compression of over 20 mmHg interferes with nerve vasculature and has adverse effects on protein synthesis, axonal transport, saltatory conduction, and myelin sheath integrity

  • Motor deficits occur first, followed by paraethesia, then muscle atrophy

  • Chronic nerve compression does not typically result in axonal damange in early stages

  • Associated comorbidities are thyroid disorders, collagen vascular disease, obesity, pregnancy, amyloidosis and diabetes

  • History:

    • Pattern of paraesthesia, pain, weakness​

    • Determine duration and rate of symptom progression

    • Relationship of symptoms to activities or extremity position

    • Nocturnal disturbance

    • Difficulty manipulating small objects, dropping items

    • Hand-arm vibratory syndrome (cold intolerance and weak pinch-grip)

  • Special tests:​

    • Vibration using tuning fork​

    • Innervation threshold with Semmes-Weinstein monofilament testing

    • Innervation density with static two point discrimination

    • Phalen's sign, Tinel's sign, Durkan's compression test

Nerve compression overview

Median nerve anatomy

  • C5-7

  • Formed from medial and lateral cords of the brachial plexus​

  • Courses between brachialis muscle and intermuscular septum medial to brachial artery

  • Passes under ligament of Struthers at the supracondylar rim

  • Crosses antecubital fossa under the bicipital poneurosis (lacertus fibrosis)

  • Diverges from the brachial artery to pass between heads of the pronator teres muscle

    • Anterior interosseous nerve (AIN) descends on the volar surface of the interosseous membrane​

      • Innervates index and middle lexor digitorum profundus (FDP) and the flexor pollicis longus (FPL), pronator quadratus (PQ)​

      • Sensation to radiocarpal, radioulnar and carpometacarpal joints

  • Continues between the FDP and FPL muscle and deep to PQ

  • In the distal forearm, it travels between FDP and flexor digitorum superficialis (FDS)

  • Travels deep to palmaris longus (PL) to enter the carpal tunnel

  • Palmar cutaneous branch of median nerve branches off approximately 5cm proximal to carpal tunnel

    • Sensation to the thenar eminence​

  • Recurrent motor nerve

    • Branching variations include beyond the transverse carpal ligament, below the ligament (subligamentous) or through the ligament (transligamentous)​

    • Motor innervation to abductor pollicis brevis (APB), opponens pollicis (OP), superficial belly of flexor pollicis brevis (FPB), index and middle lumbricals

  • Carpal tunnel

    • Floor - Carpal bones​

    • Ulnar - Hook of hamate, triquetrum, pisiform

    • Radial - Scaphoid, trapezium, fascial septum

    • Roof - Transverse carpal ligament from scaphoid tuberosity/ trapezium to pisiform and hook of hamate

    • Contents - FPL, 4 FDS, 4 FDP and the median nerve

Median nerve anatomy

Carpal tunnel syndrome

  • Overview

    • Most common upper extremity compression neuropathy​

    • Pain (worse at night) and paraesthesia over the volar hand

    • Thenar eminence is often spared of paraesthesia

  • Diagnosis

    • Weakness of thumb opposition​

    • Thenar muscle atrophy is a late sign

    • Decreased light touch sensation in median nerve distribution

    • Nerve conduction velocities shows motor latencies are usually greater than 4.5 ms and sensory latency is greater than 3.5 ms

  • Treatment​

    • Nonsurgical​

      • Wrist splint​

      • Activity modification, ergonomic workstation

      • Nonsteroidal anti-inflammatory medications

      • Steroid injection into carpal tunnel

    • Surgical​

      • Surgical release of transverse carpal ligament​

      • Re-exploration indicated if postoperative symptoms persist

      • Sensitive palmar scar is a common complication

      • Can be performed endoscopically

        • Smaller and less tender scar and faster return to work​

        • Higher rates of neurapraxia

        • Higher incidence of recurrent carpal tunnel syndrome due to incomplete transverse carpal ligament release

        • Risk of recurrent motor nerve branch injury due to inability to visualise anatomic variants

Carpal tunnel syndrome

Pronator syndrome

  • Overview

    • Median nerve adherence/ compression ​at:

      • Lacertus fibrosus​

      • Pronator teres

      • Arch of the flexor digitorum superficialis (FDS)

    • Anomalies or vascular branches in the distal forearm​

    • Entrapment beneath the ligament of Struthers between the supracondylar process of the distal humerus and fascia of the pronator teres (PT)

  • Diagnosis​

    • Tingling with tapping over PT, on elbow flexion, forearm pronation, active resistance to finger flexion​

    • Weakness of thumb interphalangeal joint (IPJ) flexion [flexor pollicis longus (FPL)] and index finger distal IPJ flexion [index flexor digitorum profundus (FDP)]

  • Treatment​

    • Surgical release indicated of ligament of Struthers, bicipital aponeurosis and tendinous arch of the FDS

Pronator syndrome

Anterior interosseous syndrome

  • Overview

    • Median nerve adherence/ compression ​at:

      • Lacertus fibrosus​

      • Pronator teres

      • Arch of the flexor digitorum superficialis (FDS)

    • Anomalies or vascular branches in the distal forearm​

    • Entrapment beneath the ligament of Struthers between the supracondylar process of the distal humerus and fascia of the pronator teres (PT)

  • Diagnosis​

    • Tingling with tapping over PT, on elbow flexion, forearm pronation, active resistance to finger flexion​

    • Weakness of thumb interphalangeal joint (IPJ) flexion [flexor pollicis longus (FPL)] and index finger distal IPJ flexion [index flexor digitorum profundus (FDP)]

  • Treatment​

    • Surgical release indicated of ligament of Struthers, bicipital aponeurosis and tendinous arch of the FDS

Anterior interosseous syndrome

Radial nerve anatomy

  • C5-7

  • Terminal branch of posterior cord

    • Bifurcates from axillary nerve running posterior to axillary/ brachial artery

  • Posterior to brachial artery and anterior to triceps/ subscapularis muscle

  • Posterior to profunda brachii artery between lateral/ medial heads of triceps

  • Transects lateral intermuscular septum with the radial collateral artery

    • 10cm proximal to distal humerus, travels​ between brachialis and brachioradialis muscle

    • Distally, enters between brachialis and extensor carpi radialis longus (ECRL) muscle

  • Radial tunnel:​

    • Floor - Radiocapitellar joint bursa​

    • Roof - Brachioradialis tendon

    • Radial - ECRL and extensor carpi radialis brevis (ECRB) tendons

    • Ulnar - Biceps tendon

    • Distal - Supinator muscle

  • 1cm lateral to the biceps tendon at the cubital fossa

  • Branches at the elbow, traverses the medial and lateral heads of supinator

    • Posterior interosseous nerve (PIN) runs deep to the arcade of Frohse and is distally adjacent to the extensor digitorum communis tendon​

      • Supplies extensor indicis propius, extensor pollicis longus and dorsal wrist capsule​

    • Superficial radial nerve is a sensory branch to the dorsal radial aspect of the hand

  • Points of radial nerve compression:​

    • Proximal to the radial tunnel​

    • Vascular leash of Henry from the radial recurrent artery

    • Proximal tendinous margin of ECRB

    • Arcade of Frohse (most common)

Radial nerve anatomy

Radial tunnel syndrome

  • Overview

    • Pain during movement at the elbow radiating distally to the dorsal hand, accompanied by tingling of the hand and weakness of grip

  • Diagnosis​

    • Pain over ECRB during forceful extension of the middle finger with the elbow held at full extension

    • Lidocaine injection into the compartment temporarily alleviates symptoms

  • Treatment​

    • Surgical release of radial nerve using anterolateral approach (between brachioradialis and brachialis muscles

    • Up to 50% of cases do not respond to surgery

Radial tunnel syndrome

Posterior interosseous nerve syndrome

  • Overview

    • Weakness and pain during finger/wrist extension without sensory involvement

    • Causes- Trauma, acute bleeding from arteriovenous malformation, rheumatoid arthritis, soft tissue mass, traction neurapraxia

  • Diagnosis​

    • Weakness in index finger extension and paraesthesia

    • Plain radiograph of elbow to assess for radial head displacement

    • Ultrasound or MRI if suspicious of soft tissue mass

    • Electrodiagnostic testing

  • Treatment​

    • Nonsurgical

      • Trial with resting splint​

      • Steroid injections

    • Surgical​

      • Surgical release of radiocapitellar joint fascia, leash of Henry, ECRB lateral edge, arcade of Frohse through anterolateral approach (between brachioradialis and brachialis muscle) and posterior approach (between EDC and ECRB muscle)

Posterior interosseous nerve syndrome

Wartenberg's syndrome

  • Overview

    • Pain during movement at the elbow radiating distally to the dorsal hand, accompanied by tingling of the hand and weakness of grip

  • Diagnosis​

    • Pain over ECRB during forceful extension of the middle finger with the elbow held at full extension

    • Lidocaine injection into the compartment temporarily alleviates symptoms

  • Treatment​

    • Surgical release of radial nerve using anterolateral approach (between brachioradialis and brachialis muscles

    • Up to 50% of cases do not respond to surgery

Wartenberg's syndrome

Ulnar nerve anatomy

  • C8-T1

  • Terminal branch of medial cord

  • Transects medial intermuscular septum in middle arm 10cm proximal to medial epicondyle to enter posterior arm

  • Covered by arcade of Struthers 8cm proximal to medial epicondyle

  • Passes medial to medial head of triceps and posterior to medial epicondyle into cubital tunnel

    • Covered by flexor carpi ulnaris (FCU) tendon/ arcuate ligament of Osborne​

    • Floor - capsule/ medial collateral ligament

    • Joint capsule/ bursa of elbow innervated by ulnar nerve

  • Passes between FCU heads and innervates them

  • Distally traverses between FDP/FDS muscle bellies and innervates ring and little FDPs

  • Travels radial to FCU tendon and ulnar to hook of hamate to enter Guyon's canal

    • Starts at proximal volar carpal ligament, ends with fibrous hypothenar origin radial to pisiform bone​

    • Roof - Volar carpal ligament

    • Ulnar - Pisiform/ FCU, pisohamate ligament, abductor digit minimi muscle

    • Radial - Hook of hamate

    • Floor - Transverse carpal ligament and hypothenar muscles

    • Neurovascular bundle and fatty tissue run below abductor and flexor digiti minimi​

    • The motor branch travels deep to the pisohamate ligament (arcuate ligament)​​

  • Innervates:​

    • Motor - palmaris brevis, dorsal interossei, palmar interossei, ring and small finger lumbricals, adductor pollicis, deep belly of flexor pollicis brevis, abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi​

    • Sensory - ring (volar and dorsal) and ulnar half of little (volar and dorsal) fingers through proper digital nerves, and hypothenar eminence and dorso-ulnar hand via dorsal branch

Ulnar nerve anatomy

Cubital tunnel syndrome

  • Overview

    • Ulnar-sided forearm tingling and pain extending to the ulnar half of the ing finger, the entire small finger, and ulnar dorsal half of the hand that may involve weakness and atrophy

    • Causes include aponeurotic compression, tumour, trauma, ulnar nerve subluxation, anatomic variation

  • Diagnosis​

    • Percussion and compression over cubital tunnel provokes symptoms

    • Recreation or increase of symptoms on elbow flexion and forearm supination

    • Froment's sign, Wartenberg's sign, ulnar partial claw hand

    • Decreased sensation in the ulnar half of ring finger, entire small finger, and ulnar dorsal half of hand

    • Decreased small finger FDP strength

    • Intrinsic muscle weakness with or without atrophy

  • Treatment​

    • Nonsurgical - Anterior elbow splint with elbow at 30° flexion

    • Surgical - Decompression of the cubital tunnel

      • Medial approach​

      • Caution to avoid damage to medial antebrachial cutaneous nerves of the forearm

      • Sites of surgical decompression

        • Arcade of Struthers​

        • Ligament of Osborne

        • Medial intermuscular septum

        • Proximal fascia between the 2 heads of FCU

        • Fascial bands within FCU tunnel

      • Results somewhat unpredictable - partial improvement may be expected

Cubital tunnel syndrome

Guyon's canal syndrome

  • Overview

    • Wrist pain with numbness, tingling and burning in the little finger and ulnar half of the ring finger

    • Causes include occupational trauma, vascular thrombosis, ulnar artery aneurysm, synovial inflammation, and carpal ganglion cyst arising from triquetrohamate joint

  • Diagnosis​

    • Weakness of intrinsic muscles of the hand, but little finger FDP normal power

    • Sensory deficit on ulnar half of ring finger and entire little finger, but sapred on dorsal ulnar hand

    • Clawing typically absent

    • Electrodiagnostic testing

  • Treatment​

    • Nonsurgical - NSAIDs, resting splint, reduction of repetitive hand motion

    • Surgical - Decompression of Guyon's canal and treatment of underlying cause

Guyon's canal syndrome
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