Carpal Tunnel Syndrome

Median nerve compression at the wrist within the carpal tunnel. The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) (the roof) and the carpal bones (the floor).

• The transverse carpal ligament is ~ 4 cm wide and directly overlies the median nerve.
• Note that, importantly, the palmar cutaneous branch of the median nerve has its takeoff ~ 5 cm proximal to the transverse carpal ligament. This proximal takeoff means that classically, the palmar cutaneous branch is superficial to the transverse carpal ligament and thus not impacted in carpal tunnel syndrome -- so the thenar eminence is spared.
• This transverse carpal ligament attaches to 4 carpal bones (pisiform, hamate, scaphoid, and trapezium):
• On the ulnar side (medially): the pisiform (proximally) and the hook of the hamate (distally).
• On the radial side (laterally): the scaphoid tuberosity (proximally) and the trapezium (distally).
• Within the carpal tunnel, the median nerve is compressed by the overlying transverse carpal ligament (the roof) and the 9 tendons beneath it.
• We can group these as the tendon(s) of flexor pollicis longus (1), flexor digitorum superficialis (4), flexor digitorum profundus (4).

Numbness and tingling in digits 1, 2, 3, and the lateral (radial) side of digit 4. In severe cases, wasting of the abductor pollicis brevis (the thenar eminence) can be observed. Paresthesias often awaken the patient from sleep (hands are flexed). Essentially any condition that either directly or indirectly increases compression within the carpal tunnel or increases tissue inflammation can be a risk factor for carpal tunnel syndrome. Predisposing Activities:

• Repetitive flexion/extension hand movements (eg, screw driver)

Specific risk factors include: Edema*: Pregnancy, Obesity Structural*: Trauma, Osteoarthritis, Tumors/Cysts Inflammatory*: Rheumatoid arthritis and other related disorders Metabolic*: Diabetes mellitus, Hypothyroidism, Amyloidosis Carpal tunnel syndrome is a clinical diagnosis that can be supported with EMG/NCS (Electromyography/Nerve Conduction Study) testing. Common provactive physical exam testing includes:

• Tinel sign
• Phalen maneuver

• Wrist splints (especially at night)
• Activity adjustment (avoid flexion/extension activities)
• NSAIDs to reduce inflammation
• Steroid injection
• Surgical decompression (division of the transverse carpal ligament)