Massage & Bodywork

May/June 2013

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4 2 The thumb's strength and stability comes from the guy-wire-like arrangement of thenar-eminence muscles (Image 2), together with the deeper adductor pollicis brevis (Image 3, semitransparent). Note the continuity of the thenar-eminence muscles with the carpal tunnel's flexor retinaculum (orange). The median (left) and ulnar (right) nerves (yellow) are also pictured. Image 3 courtesy Primal Pictures. Used by permission. 2. Since its three constituent muscles (abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis) are some of the thumb's bulkiest, the thenar eminence also provides the lion's share of palm-to-thumb grip strength (for example, when using large tools such as hammers and shovels, or in massage techniques involving squeezing or kneading). The CarPaL TunneL ConneCTion Overuse of the thenar eminence is also intimately connected to neurovascular compression and the symptoms of carpal-tunnel syndrome (such as hand, palm, or wrist pain, numbness, and tingling). Because all three of its muscles have direct connective tissue continuity with the carpal tunnel's flexor retinaculum (Image 3), repeated or heavy use of the thenar muscles can contribute to tension, strain, or shortness of this carpal ligament, which may narrow the carpal-tunnel space and compress its contents. This thenar-eminence/carpaltunnel connection works in both directions—thenar muscles can contribute to tunnel compression, and tunnel compression can cause thenar pain. While most palm muscles are innervated by the ulnar nerve (which does not pass through the carpal tunnel), the muscles of the thenar eminence are typically innervated by the median nerve (which does pass through the carpal tunnel, Image 3). It is compression of this median nerve that is most often responsible for the pain of carpal-tunnel syndrome (see "Working with Wrist and Carpal Bones," Massage & Bodywork, May/June 2009, page 122). In fact, thenar-eminence pain is one of the most common effects of median nerve compression, and atrophy of these muscles (particularly the flexor pollicis brevis, Image 4) is a possible long-term result of unresolved carpal-tunnel neurovascular compression. Direct myofascial manipulation of the thenar eminence has been anecdotally observed to lessen carpaltunnel compression symptoms, but if you notice atrophy accompanied by pain here, referral to a rehabilitative specialist is probably indicated.2 It is also important to remember that median nerve compression symptoms can be related to compression anywhere along the median nerve's length, such as at the cervical nerve roots distally through the brachial plexus, or in the arm, elbow, or forearm, not just in the hand or wrist. Thenar eMinenCe TeChniQue While it's important to keep a global perspective with respect to carpaltunnel symptoms, these symptoms aren't the only reasons to work the thenar eminence. Most anyone who uses his or her hands will truly appreciate focused local work with the structures of the thumb's base. 3 Thenar eminence/ flexor pollicis brevis atrophy (arrows) as a result of untreated median nerve compression. 4 See what benefits await you. 115

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