Carpal Tunnel Syndrome

Carpal Tunnel Syndrome (CTS) is the most common entrapment neuropathy caused by the median nerve compression at the wrist level. Early symptoms include pain, numbness, and tingling, mainly in hand. Those symptoms, unfortunately, are often being overlooked by patients and even physicians, resulting in hang hypotrophy in the later stage. Rapid response has been observed in response to short-term oral corticosteroids. Other measures include splinting, local steroid injection, and carpel ligament release surgery. To provide a better understanding of CTS, this chapter highlights the etiology, clinical features, diagnostic evaluation, management, and prognosis of this condition

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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

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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

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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
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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

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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

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  • 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

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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

Table 2: Differential diagnosis of Carpal tunnel syndrome

Conditions
Characteristics
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
Positive Spurling test
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
Positive Grind test
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

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  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
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  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
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