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Updated: Nov 13 2023

Carpal Tunnel Syndrome

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  • Summary
    • Carpal Tunnel Syndrome is a compressive neuropathy of the median nerve at the level of the wrist.
    • Diagnosis is made by clinical signs and symptoms (night pain, hand weakness/clumsiness, numbness in median nerve distribution) and positive provocative tests (i.e Tinel's, Durkan's).
    • Treatment is generally conservative with night splints and injections with carpal tunnel release reserved for refractory cases.
  • Epidemiology
    • Incidence
      • affects 0.1-10% of general population
      • Up to 70% of patients have bilateral carpal tunnel syndrome
    • Demographics
      • More common in women than men
    • Risk factors
      • female sex
      • obesity
      • pregnancy
      • hypothyroidism
      • rheumatoid arthritis
      • advanced age
      • chronic renal failure
      • smoking
      • alcoholism
      • repetitive motion activities
      • mucopolysaccharidosis (children)
      • mucolipidosis
  • Etiology
    • Pathophysiology
      • mechanism
        • exposure to repetitive vibratory exposure (e.g., typing on a keyboard)
        • certain athletic activities
          • cycling
          • tennis
          • throwing
      • pathoanatomy
        • most common causes of nerve compression
          • pathologic (inflamed) synovium - most common cause of idiopathic CTS
          • repetitive motions in a patient with normal anatomy
          • space occupying lesions (e.g., gout)
      • Associated conditions
        • diabetes mellitus
        • hypothyroidism
        • rheumatoid arthritis
        • pregnancy
        • amyloidosis
  • Anatomy
    • Carpal tunnel borders
      • scaphoid tubercle and trapezium radially
      • hook of hamate and pisiform ulnarly
      • transverse carpal ligament palmarly (roof)
      • proximal carpal row dorsally (floor)
    • Carpal tunnel contents
      • four flexor digitorum superficialis (FDS) tendons
      • four flexor digitorum profundus (FDP) tendons
      • flexor pollicis longus (FPL) 
        • most radial structure
      • median nerve
    • Median nerve
      • Terminal branch of medial and lateral cords of brachial plexus; receives input from nerve roots of C5-T1 
      • Path 
        • Travels with brachial artery between the biceps and brachialis muscles, enters antecubital fossa medial to biceps tendon
        • travels deep to the lacertus fibrosis and gives a branch to the pronator teres
      • Branches
        • Anterior interosseous nerve (AIN) 
          • AIN arises from the median nerve approximately 4 cm distal to the medial epicondyle (and 5-8 cm distal to lateral epicondyle)
          • Travels between FDS and FDP initially, then between FPL and FDP, then it lies on the anterior surface of the interosseous membrane traveling with the anterior interosseous artery to pronator quadratus
          • Terminal branches innervate the joint capsule and the intercarpal, radiocarpal and distal radioulnar joints.
        • Palmar cutaneous branch of median nerve
          • lies between PL and FCR at level of the wrist flexion crease
          • arises approximately 5 cm proximal to wrist crease
          • supplies sensation over the thenar eminence 
        • Recurrent motor branch of median nerve
          • Innervates abductor pollicis brevis, opponens pollicis, and the superficial head of the flexor pollicis brevis
          • 50% are extraligamentous with recurrent innervation
          • 30% are subligamentous with recurrent innervation
          • 20% are transligamentous with recurrent innervation
            • cut transverse ligament far ulnar to avoid cutting if nerve is transligamentous
          • Three common digital nerves supplying sensation to thumb, index, long, and radial half of ring finger 
            • Branching proper digital nerves
    • Carpal tunnel is narrowest at the level of the hook of the hamate
  • Presentation
    • Symptoms
      • numbness and tingling in radial 3-1/2 digits
      • clumsiness
      • pain and paresthesias that awaken patient at night
    • Physical exam
      • thenar atrophy
      • self administered hand diagram
        • the most specific test (76%) for carpal tunnel syndrome
      • carpal tunnel compression test (Durkan's test)
        • is the most sensitive test to diagnose carpal tunnel syndrome
        • performed by pressing thumbs over the carpal tunnel and holding pressure for 30 seconds.
          • onset of pain or paresthesia in the median nerve distribution within 30 seconds is a positive result.
      • Phalen test
        • wrist volar flexion against gravity for ~60 sec produces symptoms
        • less sensitive than Durkin compression test
      • Tinel's test
        • provocative tests performed by tapping the median nerve over the volar carpal tunnel
      • Semmes-Weinstein testing
        • most sensitive sensory test for detecting early carpal tunnel syndrome
        • measures a single nerve fiber innervating a receptor or group of receptors
      • innervation density test
        • static and moving two-point discrimination
          • A failure to discriminate two points held 5mm or less apart from one another is a positive test suggestive of CTS 
        • measures multiple overlapping of different sensory units and complex cortical integration
        • the test is a good measure for assessing functional nerve regeneration after nerve repair
    • CTS-6 Evaluation Tool: a validated clinical tool for diagnosis of CTS. A score >12 is indicative of 80% probability of CTS. A score of >5 is indicative of 25% probability.   
      • CTS-6 Evaluation Tool 
      • Numbness predominantly or exclusively in median nerve territory 
      • 3.5
      • Nocturnal Numbness 
      • 4
      • Thenar atrophy and/or weakness
      • 4/5 weakness or less 
      • 5
      • Positive Phalen test
      • 5
      • Loss of 2-point discrimination
      • Threshhold of 5mm
      • 4.5
      • Positive Tinel sign 
      • 4
  • Imaging
    • Radiographs
      • not necessary for diagnosis and not routinely indicated
    • Ultrasound 
  • Studies
    • Diagnostic criteria
      • numbness and tingling in the median nerve distribution
      • nocturnal numbness
      • weakness and/or atrophy of the thenar musculature
      • positive Tinel sign
      • positive Phalen test
      • loss of two-point discrimination
    • EMG and NCV
      • overview
        • provides objective evidence of a compressive neuropathy
          • valuable in work comp patients with secondary gain issues
        • not needed to establish diagnosis (diagnosis is clinical)
      • nerve conduction velocity (NCV)
        • prolonged latencies (slowing) of NCV
          • distal sensory latency of > 3.5 ms
          • motor latencies > 4.5 ms
        • slower conduction velocities
          • velocity of < 52 m/sec is abnormal
          • slower conduction velocity less specific than prolonged latencies
        • represents only the largest diameter, myelinated fibers in the nerve
      • electromyography (EMG)
        • test the electrical activity of individual muscle fibers and motor units
          • details insertional and spontaneous activity
        • potential pathologic findings
          • increased insertional activity
          • sharp waves
          • fibrillations
          • fasciculations
          • complex repetitive discharges
      • Electrodiagnostic study (EDS) results are associated with outcomes (prognosis) after carpal tunnel surgery
        • Patients with severe EMG/NCV findings tend to improve less than patients with middle-range findings.
    • Histology
      • nerve histology characterized by
        • edema, fibrosis, and vascular sclerosis are most common findings
        • scattered lymphocytes
        • amyloid deposits shown with special stains in some cases
  • Differential
    • AIN compressive neuropathy
    • Pronator syndrome
    • Ulnar tunnel syndrome
    • Cervical radiculopathy 
  • Diagnosis
    • Clinical and EMG/NCS
      • diagnosis can be made purely based on history and physical examination and can be confirmed with EMG/NCS.
  • Treatment
    • Nonoperative
      • NSAIDS, night splints, activity modifications
        • indications
          • first line of treatment
        • modalities
          • night splints (good for patients with nocturnal symptoms only)
          • activity modification (avoid aggravating activity)
      • steroid injections
        • indications
          • adjunctive nonoperative treatment
          • diagnostic utility in clinically and electromyographically equivocal cases
        • outcomes
          • 80% have transient improvement of symptoms (of these 20% remain symptom-free at one year)
          • failure to improve after injection is poor prognostic factor
            • surgery is less effective in these patients
    • Operative
      • carpal tunnel release
        • indications
          • failure of nonoperative treatment (including steroid injections)
            • temporary improvement with steroid injections is a good prognostic factor that the patient will have a good result with surgery)
          • acute CTS following ORIF of a distal radius fx
        • outcomes
          • pinch strength returns in 6 week
          • grip strength is expected to return to 100% preoperative levels by 12 weeks postop
          • rate of continued symptoms at 1+ year is 2% in moderate and 20% in severe CTS
          • improved patient reported-outcomes with surgery at 6 and 12 months as compared to splinting, NSAIDs/therapy, and a single steroid injection
      • revision CTR for incomplete release
        • indications
          • failure to improve following primary surgery
            • incomplete release - most common reason
        • outcomes
          • 25% will have complete relief after revision CTR
          • 50% some relief
          • 25% will have no relief
  • Technique
    • Open carpal tunnel release
      • antibiotics
        • prophylactic antibiotics, systemic or local, are not indicated for patients undergoing a clean, elective carpal tunnel release
      • technique
        • internal neurolysis, tenosynovectomy, and antebrachial fascia release do not improve outcomes
        • Guyon's canal does not need to be released as it is decompressed by carpal tunnel release
        • lengthened repair of transverse carpal ligament only required if flexor tendon repair performed (allows wrist immobilization in flexion postoperatively)
      • complications
        • correlate most closely with experience of surgeon
        • incomplete release
        • progressive thenar atrophy due to injury to an unrecognized transligamentous motor branch of the median nerve
        • lumbrical muscle weakness secondary to neuropraxia of the proper palmar digital nerve to the index finger
    • Endoscopic carpal tunnel release
      • advantage is accelerated rehabilitation
      • long term results same as open CTR
      • most common complication is an incomplete division of transverse carpal ligament
  • Prognosis
    • Good prognostic indicators include
      • night symptoms
      • short incisions
      • relief of symptoms with steroid injections
      • not improved when incomplete release of transverse carpal ligament is discovered
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