*2.5.6.1 Carpal tunnel syndrome (CTS)*

**Anatomy:** The median nerve passes between the two heads of the pronator teres muscle and reaches the forearm. In the forearm, nerve gives off branches that innervate the palmaris longus muscle, the flexor carpi radialis muscle and the flexor digitorum superficialis muscle. The palmar cutaneous branch separates from the median nerve approximately 5 cm proximal to the wrist fold. At the wrist level, the median nerve is located on the ulnar side of the flexor carpi radialis tendon and passes through the carpal tunnel [1, 16]. Carpal tunnel is lined by transverse carpal ligaments on the volar side and carpal bones on the dorsal side. In addition to the median nerve, two tendons for the 2nd, 3rd, 4th, 5th fingers (flexor digitorum superficialis and profundus) and one for the thumb (flexor pollicis longus) pass through the carpal tunnel. A total of 9 separate flexor tendon median nerves pass through the tunnel together (**Figure 16**). As the nerve passes through the carpal tunnel, it gives off motor branches that innervate the lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis muscles. Also, it provides sensory innervation of the palmar face of the radial 3,5 fingers [1, 8, 9, 35].

**Description:** Carpal tunnel syndrome is the most common peripheral nerve entrapment of the upper extremity. It is the compression of the median nerve under the carpal transverse ligament at the wrist level [8, 35].

**Causes:** Obesity, female gender, concomitant diseases (such as diabetes, pregnancy, rheumatoid arthritis, hypothyroidism, connective tissue diseases, pre-existing median mononeuropathy), repetitive wrist movements, mass lesions (eg, ganglion, lipoma, neurofibroma, fibro lipomatous hamartoma genetic predisposition and use of aromatase inhibitors are among the important causes of carpal

**Figure 16.** *The schematic drawing of the carpal tunnel and its elements.*

tunnel syndrome. Also, carpal tunnel syndrome is associated with professions that require prolonged use of hand-held vibrating hand tools and long and repeated wrist flexion and extension [1, 8, 35, 53].

**Clinical features:** The first complaint of patients with CTS is the numbness and tingling spreading to the first three fingers of the hand, and the burning and pain sensation in the wrist. This complaint is especially aggravated at night. It has been reported that complaints were reduced by waving the hand. As the motor fibers begin to be affected over time, atrophy begins to occur in the lumbrical muscles of the 2nd and 3rd fingers, and the patient's hand weakness, incompetence (dropping something from the hand, inability to do fine hand skills) begins to develop [1, 8, 35, 53].
