History
Patients typically complain of an intermittent "pins-and-needles" paresthesia in the median nerve distribution of the hand. Pain is generally worse at night than during the day. Patients may awaken with a burning pain or tingling that may be relieved with shaking their hands. Classic carpal tunnel syndrome (CTS) is associated with symptoms that affect at least 2 of the first through third digits; symptoms affecting the fourth and fifth digits, wrist pain, and radiation of pain proximal to the wrist may also occur, but classic CTS is not associated with symptoms on the palm or dorsum of the hand. [13]
Symptoms of probable CTS are the same as classic CTS except palmar symptoms may be present, unless confined solely to the ulnar aspect. Possible CTS involves symptoms in at least one of the first 3 digits. The sensitivity of classic or probable CTS symptoms for diagnosing CTS is 80%. CTS is unlikely if no symptoms are present in any of the first 3 digits. [13]
Symptoms are most often bilateral, insidious in onset, and progressive in nature. With advanced nerve compression, an aching sensation is persistent and static and may radiate to the forearm and elbow. Enquire with regard to repetitive strain risk, such as waitperson, assembly packing, computer keyboard work, playing a musical instrument, or craftwork. Determine if any significant trauma has occurred. The presence of symptoms in the ring and small finger may be much more common than previously thought. [20]
Physical
Weakness of resisted thumb abduction (ie, movement of the thumb at right angles to the palm) is helpful in determining which patients will have an electrodiagnosis of CTS. [21]
Sensory hypalgesia as demonstrated by diminished ability to perceive painful stimuli applied along the palmar aspect of the index finger when compared with the ipsilateral little finger also is associated with the electrodiagnosis of CTS. [21]
Hyperflexion of the wrist for 60 seconds may elicit paresthesia in the median nerve distribution (ie, Phalen sign). A literature review showed the average sensitivity and specificity of the Phalen sign to be 68% and 73%, respectively. [3]
Tapping the volar wrist over the median nerve (ie, Tinel sign) may produce paresthesia in the median distribution of the hand. Pooled data show the sensitivity and specificity of the Tinel sign to be 50% and 77%, respectively. [3]
Shaking or flicking one's hands for relief during maximal symptoms (ie, Flick sign) has been shown to have a sensitivity of 47% and specificity of 62%. [3]
The loss of 2-point discrimination in the median nerve distribution or abductor pollicis brevis atrophy has a high specificity (>90%) but low sensitivity (< 25%). [3]
Causes
Causes of carpal tunnel syndrome include the following:
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Inflammation of the flexor tendon sheath caused by activities involving repetitive wrist flexion (eg, assembly packing, computer keyboard work, playing a musical instrument, craftwork)
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Edema from trauma of any type (eg, fractures), which can compress the median nerve
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Compression of the median nerve from pregnancy [22] or oral contraceptive–related edema
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Strong association between being overweight or obese and the presence of CTS
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Renal failure and hemodialysis
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Chemotherapy for breast cancer (anastrozole) [23]
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Carpal tunnel syndrome. Carpal and Guyon tunnels. Drawing showing the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). The flexor retinaculum (medium gray region) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region) forms the volar boundary of the Guyon tunnel. * = flexor pollicis longus tendon, * = flexor carpi radialis tendon. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Carpal tunnel syndrome. Carpal and Guyon tunnels. Transverse 5-12-MHz ultrasound scan corresponding to the image above shows the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. The flexor retinaculum (open arrowheads) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. * = flexor pollicis longus tendon. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Carpal tunnel syndrome. Carpal and Guyon tunnels. Drawing showing the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region) forms the roof of the carpal tunnel. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Carpal tunnel syndrome. Carpal and Guyon tunnels. Transverse 5-12-MHz ultrasound scan corresponding to the image above shows the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (open arrowheads) forms the roof of the carpal tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. * = flexor pollicis longus tendon. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Carpal tunnel syndrome. Normal findings on an axial spin-echo T1 MRI of the carpal tunnel showing the intermediate signal intensity of the median nerve (arrow).
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Carpal tunnel syndrome. Normal findings of isointense-to-hypointense appearance of the median nerve on fast spin-echo T2-weighted MRI (arrow). Note the fairly well-defined nerve fascicles within the median nerve sheath.
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Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with fat saturation. Note the increased T2-weighted signal within the median nerve (arrow). A slightly increased cross sectional area of the nerve is noted but the nerve architecture is preserved, consistent with early or mild inflammation.
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Carpal tunnel syndrome. Fast spin-echo T2-weighted MRI illustrates more pronounced increased signal within the median nerve (arrow). Note the small amount of fluid within the carpal tunnel, a secondary sign of inflammation. Slightly less optimal fat saturation is noted than on other images, which is a common occurrence.
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Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with greater increase in signal and loss of definition within the nerve (arrow). Inflammatory change is noted within the carpal tunnel, adjacent to the flexor digitorum superficialis tendons. The appearance is consistent with pronounced inflammatory change within the carpal tunnel.
