Carpal Tunnel Syndrome

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Jan 27, 2022
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Introduction

  • Carpal tunnel syndrome (CTS) is a peripheral neuropathy caused by compression of the median nerve as it passes under the transverse carpal ligament at the wrist.
  • Symptoms consist of pain, numbness, and tingling; mostly in the hand
  • Treatment includes non-surgical and surgical management
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Most common entrapment neuropathy. Covers up to 90% of all neuropathies

Etiology

  • Previous wrist fracture
  • Occupational factor
    • Exposure to hand-transmitted vibration
    • Repeated and forceful activities of the wrist
  • Pregnancy
  • Rheumatoid arthritis
  • Osteoarthritis
  • Obesity
  • Diabetes
  • Other systemic disorders
    • Systemic amyloidosis
    • Hypothyroidism
    • Acromegaly

Innervation of the median nerve at the hand

Table 1: The Median Nerve Motor Distribution

Muscle
Function
Thenar muscles
Abductor pollicis brevis
Thumb abduction
Opponens pollicis
Thumb opposition
Flexor pollicis brevis (superficial head)
Thumb flexion
Intrinsic muscles
Lumbricals I-II
- MCP flexion at the joint - PIP and DIP extension
MCP: MetaCarpoPhalangeal ; PIP: Proximal InterPhalangeal; DIP: Distal InterPhalangeal

Figure 1: Superficial muscles of the hand (Palmar view of the left hand)

CFCF. (2015, October 14). English: Based off: Wikimedia Commons. https://commons.wikimedia.org/wiki/File:1121_Intrinsic_Muscles_of_the_Hand_Superficial_sin.png ‌
CFCF. (2015, October 14). English: Based off: Wikimedia Commons. https://commons.wikimedia.org/wiki/File:1121_Intrinsic_Muscles_of_the_Hand_Superficial_sin.png

Figure 2: The Median Nerve Sensory Distribution

notion image
 

Pathophysiology

  • The carpal tunnel is a narrow osteofibrous outlet, lying between the transverse carpal ligament and the carpal bones, which contains flexor tendons and the median nerve
  • ↑ carpal tunnel pressure → compression of components within a confined space, including the median nerve → altering in the median nerve’s microvascular structure → ↓ endoneurial blood flow → edema and hypoxia → axonal degeneration

Figure 3: The Carpal Tunnel Cross Section

notion image

Clinical features

Mild to Moderate

  • Symptoms progress within the distribution of the median nerve, including the palmar aspect of the thumb, index, middle fingers, and radial half of the ring finger
    • Pain
    • Numbness/tingling/burning sensation
  • Worsen at night or after repetitive motions
💡
The palmar branch arises from the median nerve ABOVE the wrist level → NO sensory loss in the thenar eminence

Moderate to Severe

  • Symptoms mentioned above, plus motor dysfunction (weakening opponens pollicis, abductor pollicis brevis, and superficial head of the flexor pollicis brevis)
    • Weakened grip strength → dropping objects
    • Thenar atrophy → loss thumb opposition

Figure 4: Thenar atrophy

notion image

Diagnostics Evaluation

Provocative tests

  • Phalen’s maneuver
    • Holds the patient's wrist in full flexion (90°)
    • Paresthesia occurs or worsens in the median nerve distribution within one minute → positive
    • Sensitivity: 57%. Specificity: 58%

Figure 5: Phalen’s maneuver illustration

notion image
  • Tinel’s sign
    • Taps over the carpal tunnel with fingertips or a reflex hammer
    • Shooting pain and/or numbness/tingling in the median nerve distribution → positive
    • Sensitivity: 36%. Specificity: 75%

Figure 6: Tinel’s sign illustration

notion image
 

Electrophysiological studies

  • Nerve conduction studies (NCS)
    • Confirm the diagnosis
    • Velocity decrease (prolongation of the distal motor and sensory latency)
  • Electromyography (EMG)
    • Evaluate the severity
    • Surgical prognosis

Differential Diagnosis

Cervical radiculopathy C6 or C7

  • Neck pain radiating to the shoulder and the forearm
  • Weakness of elbow flexion, extension, and arm pronation
  • Upper extremities hyporeflexia

Median neuropathy above the carpal tunnel

  • Impaired palmar cutaneous nerve → thenar eminence sensory loss
  • More proximal median-innervated muscles involvement (thumb flexion, wrist flexion, and arm pronation)

Arthritis

  • Rheumatoid arthritis, osteoarthritis, or other inflammatory arthropathies
  • Usually bilateral involvement
  • X-ray findings
  • Other lab findings

De Quervain tendinopathy

  • Tenderness at the distal radial styloid

Hereditary neuropathy with liability to pressure palsy (subvariant of Charcot-Marie-Tooth disease)

  • Autosomal dominant disorder
  • Nerve entrapment in multiple areas

Management

Mild to moderate

  • Conservative management
    • Lifestyle Modification
      • Avoiding repetitive motions
      • Using ergonomic devices (ergonomic keyboard, mouse pad, wrist rest)
      • Using voice recognition and dictation devices
    • Short-term oral corticosteroids
      • Prednisone 20 mg daily for the first week; 10 mg daily for the second week
      • Rapid response
      • Gradually wanes over 8 weeks after medication is discontinued
    • Splinting
      • Neutral and cock-up wrist splints deliver similar symptoms relief outcomes
      • Over-night splinting alone can reduce symptom severity and improve median nerve conduction velocities
      • Follow up for 06-08 weeks
    • Local corticosteroid injection
      • Bolus injection of 20 mg Triamcinolone acetonide without lidocaine beneath the transverse carpal ligament
      • In mild cases, a symptoms-free period might be up to one month after the injection
      • May be used as an adjuvant therapy before surgery
      • Carry a risk of median nerve injury

Moderate to severe (or fail conservative management)

  • Relieves symptoms significantly more than splinting, but not more than local corticosteroid injection

Figure 7: Open carpal tunnel release surgery

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Prognosis

  • If left untreated → Progress over time and can cause permanent median nerve damage
  • ~90% of mild to moderate cases improve with conservative management only
  • Up to one-third of the patients have recurring symptoms 5 years after surgery

Further Reading

  • Wright, A. R., & Atkinson, R. E. (2019). Carpal Tunnel Syndrome: An Update for the Primary Care Physician. Hawai'i journal of health & social welfare78(11 Suppl 2), 6–10.
  • Żyluk A. (2020). The role of genetic factors in carpal tunnel syndrome etiology: A review. Advances in clinical and experimental medicine : official organ Wroclaw Medical University29(5), 623–628. https://doi.org/10.17219/acem/118846

Bibliography

  1. Aboonq M. S. (2015). Pathophysiology of carpal tunnel syndrome. Neurosciences (Riyadh, Saudi Arabia), 20(1), 4–9.
  1. Geoghegan, J. M., Clark, D. I., Bainbridge, L. C., Smith, C., & Hubbard, R. (2004). Risk factors in carpal tunnel syndrome. Journal of hand surgery (Edinburgh, Scotland), 29(4), 315–320. https://doi.org/10.1016/j.jhsb.2004.02.009
  1. Herskovitz, S., Berger, A. R., & Lipton, R. B. (1995). Low-dose, short-term oral prednisone in the treatment of carpal tunnel syndrome. Neurology, 45(10), 1923–1925. https://doi.org/10.1212/wnl.45.10.1923
  1. LeBlanc, K. E., & Cestia, W. (2011). Carpal tunnel syndrome. American family physician, 83(8), 952–958.
  1. Palmer K. T. (2011). Carpal tunnel syndrome: the role of occupational factors. Best practice & research. Clinical rheumatology, 25(1), 15–29. https://doi.org/10.1016/j.berh.2011.01.014
  1. Sevy JO, Varacallo M. Carpal Tunnel Syndrome. [Updated 2021 Sep 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448179/
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