Carpal Tunnel Syndrome

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Definition & Anatomy - Tunnel Trouble

  • Definition: Median nerve entrapment neuropathy at the wrist within the carpal tunnel.
  • Carpal Tunnel Borders:
    • Roof (Volar): Transverse Carpal Ligament (TCL).
    • Floor (Dorsal) & Walls: Carpal bones (concave arch).
  • Contents (10 structures): 📌 1 Median nerve, 9 tendons:
    • 4 Flexor Digitorum Superficialis (FDS).
    • 4 Flexor Digitorum Profundus (FDP).
    • 1 Flexor Pollicis Longus (FPL). Carpal Tunnel Anatomy: Median Nerve & Tendons

⭐ The palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel and passes superficial to the TCL, thus sensation over the thenar eminence is typically spared in CTS.

Etiology & Risk Factors - Squeeze Factors

  • Increased Volume of Tunnel Contents:
    • Fluid accumulation: Pregnancy (edema), hypothyroidism (myxedema), heart failure.
    • Inflammatory swelling: Tenosynovitis (e.g., Rheumatoid Arthritis, gout), infection.
    • Mass lesions: Ganglion cysts, lipomas, tumors.
    • Hemorrhage: Post-traumatic hematoma.
  • Decreased Carpal Tunnel Space:
    • Bony encroachment: Distal radius fracture malunion, lunate dislocation, osteophytes (OA).
    • Soft tissue thickening: Acromegaly.
    • External compression: Constrictive casts/splints.

⭐ Sustained wrist flexion or extension dramatically ↑ intracarpal pressure.

Clinical Features - Nerve Numbness

  • Sensory (Early):
    • Pain & paresthesia (tingling, burning) in median nerve distribution:
      • Thumb, index, middle, radial half of ring finger.
      • Spares thenar eminence (palmar cutaneous branch).
    • Nocturnal paresthesia: Awakens patient; classic.
    • Flick sign: Shaking hand for relief.
  • Motor (Late):
    • Thenar muscle weakness (Abductor Pollicis Brevis - APB).
    • Difficulty with fine motor tasks, e.g., buttoning.
    • Thenar atrophy (severe cases: ape-hand deformity).
    • Clumsiness, dropping objects. Median nerve anatomy, damage, diagnosis, and treatment

⭐ Sparing of sensation over the thenar eminence is key; the palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel and does not pass through it.

Diagnosis & Tests - Pinpointing Pain

  • Provocative Tests:
    • Phalen Test: Wrist flexion for 60s → symptoms.
    • Tinel Sign: Tap over median nerve → symptoms.
    • Durkan Test (Carpal Compression): Direct pressure over carpal tunnel for 30s → symptoms.
  • Electrodiagnostic Studies (NCS/EMG):
    • Gold standard for confirmation & severity.
    • Key Findings:
      • ↓ Sensory/motor nerve conduction velocity (NCV) across tunnel.
      • ↑ Distal motor latency (DML > 4.5 ms).
      • ↑ Distal sensory latency (DSL).
      • EMG: Thenar denervation (severe cases).
  • Imaging:
    • Ultrasound (USG): Median nerve cross-sectional area (CSA) > 10-12 mm² at inlet/pisiform.
    • MRI: Not routine; for suspected mass, atypical presentation, or failed surgery.

Ultrasound: Normal vs. Carpal Tunnel Median Nerve

⭐ The Carpal Compression Test (Durkan Test) is often considered the most sensitive provocative clinical test for Carpal Tunnel Syndrome (CTS).

Management - Releasing Relief

  • Conservative (Mild-Moderate Symptoms):

    • Wrist Splinting: Neutral position, especially at night.
    • NSAIDs: Symptomatic relief.
    • Corticosteroid Injections: Intra-carpal; diagnostic & temporary relief.
    • Activity Modification: Ergonomic changes, avoid triggers.
    • Yoga & Physical Therapy.
  • Surgical (Carpal Tunnel Release - CTR):

    • Indications:
      • Failure of >3-6 months conservative trial.
      • Thenar muscle atrophy or weakness.
      • Progressive sensory loss.
      • Severe symptoms or EMG evidence of denervation.
    • Techniques:
      • Open CTR: Standard, direct visualization.
      • Endoscopic CTR (ECTR): Smaller incision, potentially faster initial recovery.

⭐ Night-time wrist splinting in a neutral position is often the most effective initial conservative treatment for mild to moderate Carpal Tunnel Syndrome.

High-Yield Points - ⚡ Biggest Takeaways

  • Caused by median nerve compression within the carpal tunnel, it's the most common entrapment neuropathy.
  • Classic symptoms: nocturnal pain and paresthesia in the thumb, index, middle, and radial half of the ring finger.
  • Thenar muscle atrophy and weakness are significant late findings.
  • Key provocative tests include Phalen's maneuver (wrist flexion), Tinel's sign (percussion over nerve), and Durkan's test (carpal compression).
  • Nerve Conduction Studies (NCS) are the gold standard for confirming diagnosis and assessing severity.
  • Treatment progresses from conservative (e.g., night splinting, steroid injections) to surgical carpal tunnel release.
  • Strongly associated with conditions like diabetes mellitus, hypothyroidism, rheumatoid arthritis, and pregnancy due to fluid retention or connective tissue changes.

Practice Questions: Carpal Tunnel Syndrome

Test your understanding with these related questions

A patient at the orthopedics OPD complains of troubled sleep at night due to numbness and tingling sensation involving his lateral 3 digits. His symptoms are relieved as he lays his arms hanging from the bed. Which of the following options correctly describes his condition and the test used to assess it?

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Flashcards: Carpal Tunnel Syndrome

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Dislocation of the _____ (bone) may cause acute carpal tunnel syndrome.

TAP TO REVEAL ANSWER

Dislocation of the _____ (bone) may cause acute carpal tunnel syndrome.

lunate

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