From the Guidelines
Muscle wasting associated with carpal tunnel syndrome primarily affects the thenar muscles of the hand, particularly the abductor pollicis brevis, opponens pollicis, and the superficial head of the flexor pollicis brevis. These muscles form the thenar eminence, which is the fleshy mound at the base of the thumb. In carpal tunnel syndrome, the median nerve becomes compressed as it passes through the carpal tunnel in the wrist, leading to impaired nerve function. Since the median nerve innervates these thenar muscles, prolonged compression results in denervation and subsequent atrophy of these muscles. This muscle wasting is often visible as a flattening of the thenar eminence and can lead to weakness in thumb opposition and abduction, making fine motor tasks difficult. The severity of muscle wasting correlates with the duration and degree of nerve compression, with advanced cases showing significant functional impairment. Early intervention for carpal tunnel syndrome is crucial to prevent permanent muscle atrophy and functional loss, as supported by the findings of a Cochrane review 1, which compared carpal tunnel surgery with non-surgical treatment and found surgery to be more effective in most outcome measures. Key points to consider in the management of carpal tunnel syndrome include:
- The importance of early diagnosis and treatment to prevent long-term nerve damage and muscle atrophy
- The role of surgical intervention, such as open or endoscopic release, in relieving symptoms and improving functional status, as discussed in the study 1
- The potential benefits and risks of different treatment approaches, including the risk of nerve injury associated with endoscopic release, as noted in the study 1
From the Research
Muscle Wasting with Carpal Tunnel Syndrome
- Muscle wasting associated with carpal tunnel syndrome is often characterized by thenar atrophy, which affects the muscles of the thumb, particularly the abductor pollicis brevis (APB) 2.
- The APB muscle is responsible for thumb abduction and is commonly affected in cases of carpal tunnel syndrome, leading to weakness and atrophy of the thenar muscles 2, 3.
- Other hand muscles, such as the lumbrical muscles, palmaris longus, and flexor digitorum superficialis, can also be affected by carpal tunnel syndrome, although the APB muscle is the most commonly associated with muscle wasting 4.
- The severity of muscle wasting can vary, with some patients experiencing mild or no muscle atrophy despite having severe carpal tunnel syndrome 3.
- Muscle coherence and force coordination during precision pinch can be affected by carpal tunnel syndrome, particularly when the wrist is in a flexed position 5.