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Ann Thorac Surg 2000;69:666
© 2000 The Society of Thoracic Surgeons

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Correspondence

Median-innervated intrinsic hand muscles

^a Clinical Neurophysiology Laboratories, University of California, San Francisco, CA 94143-0114, USA

To the Editor

In correspondence recently published in The Annals of Thoracic Surgery [1, 2] concerning a 1997 article by Urschel and Razzuk [3] on thoracic outlet syndrome, the motor root origin of the axons that supply the median nerve–innervated intrinsic hand muscles, the opponens pollicis and abductor pollicis brevis, was debated. Wilbourn and Cherington [1] claimed that these muscles are innervated by the C8 and T1 roots, whereas Urschel and associates [2] contended that they were, in fact, innervated by the C6 and C7 roots. The root origin of these fibers was central to the claim of Urschel and coauthors [2] that median motor nerve conduction studies can be used to assess "the upper plexus" (ie, fibers derived from the C5 to C7 roots).

I do not wish to comment directly on the central argument regarding the value of nerve conduction studies in assessing patients considered to have neurologic thoracic outlet syndrome other than that associated with a cervical rib and band, because my associates and I [4] have expressed views on this topic previously. It is important, however, for your readers to know that there is little active debate regarding the innervation of these hand muscles: there is almost unanimous agreement that they are innervated by the C8 and T1 roots by way of the lower trunk and medial cord of the brachial plexus.

It appears that Urschel and colleagues [2] were misled by incorrect information that appeared in one of the older American editions of Gray’s Anatomy. The latest American edition of that book [5], published in 1985, contains corrected information, namely, that the opponens pollicis and abductor pollicis brevis are innervated by the C8 and T1 roots. Thus, the latest American edition now aligns itself on this point with several of the English editions of Gray’s Anatomy, including the latest one [6].

References

1. Wilbourn A.J., Cherington M. Diagnosing upper plexus thoracic outlet syndrome with median motor nerve conduction studies. Ann Thorac Surg 1999;67:290-291.[Free Full Text]
2. Urschel H.C., Jr, Razzuk M.A., Crane C.R. Reply. Ann Thorac Surg 1999;67:291-292.[Free Full Text]
3. Urschel H.C., Jr, Razzuk M.A. Upper plexus thoracic outlet syndrome. Ann Thorac Surg 1997;63:935-939.[Abstract/Free Full Text]
4. Aminoff M.J., Olney R.K., Parry G.J., Raskin N.H. Relative utility of different electrophysiolgoic techniques in the evaluation of brachial plexopathies. Neurology 1988;38:546-550.[Abstract/Free Full Text]
5. Gray’s anatomy. 30th ed. (American). Philadelphia: Lea & Febiger, 1985:550.
6. Gray’s anatomy. 38th ed. (English). New York: Churchill Livingstone, 1995:589.

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