Compressive Neuropathies

• Median Nerve
• Carpal Tunnel Syndrome
• Associated with conditions that increase tissue deposition (multiple myeloma, rheumatoid arthritis, amyoidosis, acromegaly, mucopolysaccharidosis, hypothyroidism, pregnancy, diabetes)
• Compression of motor branches deep to transverse carpal ligament
• Paresthesias in the median nerve distribution, most severe at night (nocturnal dysesthesias), hypesthesia
• In advanced cases – weakness of abduction/opposition of thumb, wasting of lateral thenar eminence from weakness of LOAF muscles (lumbricals 1-2, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)
• Phalan’s test – wrist flexion for 30-60 sec exacerbates pain/numbness/paresthesias (80% positive)
• Tinel’s test – percussion over nerve at wrist (60% positive)
• Nerve conduction velocities normal in 25% of patients (sensory latency more sensitive than motor)
• EMG shows abnormalities in median nerve conduction at wrist
• Treatment:
• Splinting of wrist in neutral position (wrist cock-up in splints)
• Surgical decompression
• Pronator teres syndrome – median nerve between heads of pronator teres
• Generally no nocturnal symptoms (unlike carpal tunnel)
• Ache, fatigue of grip (especially thumb to index finger), paresthesias
• Numb palm (palmar cutaneous branch travels over transverse carpal ligament and is spared with carpal tunnel)
• Struther’s ligament – median nerve compression at elbow
• medial epicondyle to supracondylar process (anatomic variant); median nerve/brachial artery passes underneath
• Anterior interosseous nerve – median – weakness without sensory loss – affects pronator quadratus, flexor pollicis longus, flexor digitorum profundus 1-2, pinch sign (poor thumb and distal phalanx flexion
• Ulnar Nerve
• Pain in medial forearm/hand, inability to extend 4^th and 5^th fingers (“claw hand”), Froment’s sign (substituting flexion for adduction of thumb to grasp item between thumb and 1^st finger), interosseus and hypothenar atrophy
• claw hand (ulnar supplies lumbricals 4-5 – flex PIP, extend MCP), Wartenburg’s sign (cannot adduct 5^th finger due to weak third palmar interosseous muscle)
• Entrapment may occur at the elbow or wrist
• Arcade of Struthers – ulner nerve compression at medial head of triceps
• Cubital tunnel – ulnar nerve compression by heads of flexor carpi ulnaris
• Guyon’s Canal – ulnar nerve compression between transverse carpal ligament and palmaris fascia at wrist
• Etiology:  Direct trauma, recurrent subluxation of the nerve, cubital tunnel syndrome, compression from adjacent elbow structures
• Diagnosis:
• Tinel’s sign over ulnar nerve, especially at elbow
• EMG shows abnormalities in ulnar nerve conduction
• Treatment: Surgical decompression with or without transposition
• Radial Nerve
• Complete wrist drop, digital extensor paralysis, sensory deficit over posterior hand
• Entrapment usually occurs at elbow, but may occur above the elbow
• Spiral groove/intramuscular septum – of upper arm; causes wrist drop without triceps weakness
• Posterior interosseous nerve – radial – affects supinator, extensor digitorum, extensor carpi ulnaris, abductor pollicis longus, sensation over dorsolateral forearm and hand; finger extension weakness without wrist drop or sensory loss
• Radial tunnel – elbow pain without weakness “Saturday night palsy” – frequently follows a drunken sleep during which time the arm is allowed to hang off the bed, spares triceps
• Crutch palsy – secondary to improper crutch walking, triceps involved
• Displaced humeral shaft fractures

o Treatment: Surgical decompression

• Suprascapular Nerve
• Usually entrapped at suprascapular notch by transverse scapular ligament; can also be entrapped at level of scapular spine
• Causes atrophy of supraspinatous/infraspinatous muscles
• Treatment: surgical decompression
• Lateral Femoral Cutaneous Nerve (L2-3)
• Meralgia paresthetica – entrapment beneath inguinal ligament – anterolateral thigh numbness/dysesthesia, caused by obesity/pregnancy/diabetes
• Peroneal Nerve
• common peroneal nerve behind fibular head – weakness of EHL, tibialis anterior, toe extensors; may have sensory change
• Tibial Nerve
• Tarsal tunnel syndrome – posterior tibial nerve entrapment inferior to lateral malleolus, paresthesias of toes and sole of foot, often no motor abnormality but can have weakness of intrinsic foot muscles