Opponens Pollicis

Median Nerve, Medial Cord, Anterior Division, Lower Trunk, C8, Tl. 

This muscle inserts into the lateral half of the palmar surface of the 1st Metacarpal. It lies deep to the Abductor Pollicis Brevis and lateral to the Flexor Pollicis Brevis. 

Midpoint of a line drawn between the radial aspect of the carpometacarpal (C-MC) and the metacarpophalangeal joints (MP-I). 

The electrode is placed between the abductor pollicis brevis and the 

If the electrode is inserted too deeply it will be in the adductor pollicis. If placed too medially it will be in the abductor pollicis brevis. 

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Studies Blood chemistries including thyroid and parathyroid tests are normal. Nerve conductions showed severe bilateral dyssdiwannian neuropathy of the median nerves, with prominent conduction block across both wrists. Nerve conductions across the elbow and elsewhere were normal. BMG showed, in both hands, slight-moderate recent denervation in the opponens pollicis and abductor pollicis brevis. Nerve conductions and BMG in the lower limbs were normal. 

The thenar muscles are innervated by the recurrent branch of the median nerve and are basically responsible for the complex movement of the thumb. They include the superficial abductor pollicis brevis, the flexor pollicis brevis and the deep opponens pollicis muscles. The abductor pollicis brevis is a broad flat muscle located on the more lateral side of the thenar eminence. It arises from the radial side of the transverse carpal ligament and the tubercle of the trapezium and inserts into the base of the proximal phalanx. The flexor pollicis brevis is located medial to the abductor pollicis and has two muscular bellies the superficial head arises from the transverse carpal ligament and the tubercle of the trapezium, the deep head (first palmar interosseous muscle) from the trapezoid and the capitate. Both heads insert through the radial sesamoid over the metacar-... 

Fig. 10.47a-c. Ape hand deformity in the right hand of a patient with severe median neuropathy at the carpal tunnel level, a Photograph of the palmar aspect of the hand reveals a skin depression (arrows) due to loss in bulk of the intrinsic muscles at the thenar eminence, b Transverse 12-5 MHz US image at the dorsal aspect of the hand demonstrates a hyperechoic appearance of the abductor pollicis brevis (asterisk) and opponens poUicis (star) related to neurogenic fatty atrophy, d Contralateral healthy side. The insert at the upper right side of the figure indicates probe positioning... 

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