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Updated: Aug 21 2023

Carpal Tunnel Syndrome

4.3

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Images
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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
    • Risk factors
      • female sex
      • obesity
      • pregnancy
      • hypothyroidism
      • rheumatoid arthritis
      • advanced age
      • chronic renal failure
      • smoking
      • alcoholism
      • repetitive motion activities
      • mucopolysaccharidosis
      • mucolipidosis
  • Etiology
    • Pathophysiology
      • mechanism
        • exposure to repetitive motions and vibrations
        • 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
    • Branches of median nerve
      • palmar cutaneous branch of median nerve
        • lies between PL and FCR at level of the wrist flexion crease
      • recurrent motor branch of median nerve
        • 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
    • 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 tunnels 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
        • 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
  • Imaging
    • Radiographs
      • not necessary for diagnosis
  • 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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