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Sectional Neuroanatomy of the Upper Limb II: Shoulder and Upper Arm

Liu, Shirley; Taber, Katherine H.; Duncan, Gregory; Chiou-Tan, Faye; Hayman, L. Anne

Journal of Computer Assisted Tomography: January-February 2001 - Volume 25 - Issue 1 - p 154-157
Graphic Anatomy

This article is the second in a series of three that presents an anatomic functional guide to the peripheral innervation of the shoulder and upper limb. It illustrates the axial anatomy of the shoulder and upper arm. The next article continues this format for the lower arm and hand. Together, all three papers can be used to rapidly identify each upper limb muscle and its innervation(s). They can also be used to locate the peripheral nerve trunks, and correlate lesions with the classic pattern(s) of muscle denervation and altered sensation.

From the Department of Radiology (S. Liu, K. H. Taber, L. A. Hayman), Herbert J. Frensley Center for Imaging Research (S. Liu, K. H. Taber, L. A. Hayman), Department of Psychiatry & Behavioral Sciences (K. H. Taber, L. A. Hayman), Department of Molecular and Cellular Biology (G. Duncan), and Department of Physical Medicine & Rehabilitation (F. Chiou-Tan), Baylor College of Medicine, Houston, TX 77030, U.S.A.

Address correspondence and reprint requests to Dr. L. A. Hayman, Department of Radiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030-3498, U.S.A. E-mail:

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Magnetic resonance (MR) imaging of the brachial plexus and upper limb holds the possibility of directly visualizing nerve lesions and detecting diagnostically useful patterns of muscle denervation (1). This would be a significant contribution since clinical examination often elicits only vague motor and sensory deficits. To assist the radiologist in interpreting these images, the authors have created a much-needed functional anatomic atlas. It is designed to orient the reader despite the wide variations in the shape and size of the upper limb muscles. It illustrates the most common patterns of motor and sensory innervations. Individual anatomic differences and partial nerve injuries will, of course, produce variations or patchy denervation patterns, respectively (2–4).

While the first article in this series provided sagittal anatomic schematics of the brachial plexus (1), this article provides axial anatomic schematics of the shoulder and upper arm (Fig. 1). Both use the same format for numbering and color-coding the muscles according to the classic patterns of peripheral nerve innervation (2–6). Muscles with two sources of nerve supply are shaded with the designated colors of both nerves. Table 1 summarizes the expected patterns of muscle denervation following total nerve lesions at seven of the axial levels. Note that only muscles distal to the lesion will be fully denervated. A positive correlation between MR imaging abnormalities in or around a nerve and the distal muscle denervation pattern increases the probability that the lesion is, in fact, clinically significant. For example, the clinical significance of a lesion surrounding the nerves in the axilla at level C would be determined by assessing the muscles supplied by the musculocutaneous, radial, median, and ulnar nerves. Although the suprascapular, axillary, and long thoracic nerves do not fall within the axial sections chosen for the atlas, injury to these structures can be inferred if patchy changes of muscle denervation are seen in the muscles they supply.

FIG. 1.

FIG. 1.

FIG. 1.

FIG. 1.

Injury to the nerves in the axilla and upper limb occurs in a variety of clinical settings. An unconscious patient can externally compress the axilla (axillary crutches) or the nerves of the upper arm (“Honeymooner's Palsy” or “Saturday Night Palsy”). These nerves can also be injured by neoplasms or hematomas, and as a result of postprocedure complications after anesthesia or axillary angiography (7). Imaging could play a vital role by detecting the extent of injury, determining the prognosis, and deciding if surgical intervention or exploration is needed. It could also contribute to the planning of occupational therapy.

The next article will provide the same information for the lower arm and hand. Together, the three articles comprise a guide that can be used to 1) predict the clinical picture for a given plexal or peripheral nerve lesion, or 2) directly detect nerve involvement, or 3) extrapolate lesion location when a constellation of denervated muscles are seen on upper limb magnetic resonance imaging or an electromyographic study.

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1. Taber KH, Maravilla K, Chiou-Tan F, Hayman LA. Sectional neuroanatomy of the upper limb I: Brachial plexus. J Comput Assist Tomogr 2000; 24:983–6.
2. Hollinshead WH. General survey of the upper limb. In: Hollinshead WH, ed. Anatomy for Surgeons: The Back and Limbs. 2nd Ed. New York: Harper & Row, 1999:247–58.
3. Christoforidis AJ. Atlas of Axial, Sagittal, and Coronal Anatomy with CT and MRI. Philadelphia: Saunders, 1988:1–563.
4. el-Khoury GY. Sectional Anatomy by MRI/CT. New York: Churchill Livingstone, 1990:1–733.
5. Lumley JSP. Upper limb. In: Lumley JSP, ed. Surface Anatomy. 2nd Ed. Edinburgh, Scotland: Churchill Livingstone, 1996:56–83.
6. Ellis H, Logan BM, Dixon AK. Upper limb. In: Ellis H, Logan BM, Dixon AK, Eds. Human Sectional Anatomy: Atlas of Body Sections, CT and MRI Images. 2nd Ed. Oxford: Butterworth Heinemann, 1999:221–42.
7. Dumitru D. Electrodiagnostic Medicine. 1st Ed. Philadelphia: Hanley and Belfus, 1995:585–685.

MR, upper limb; Electromyography, brachial plexus; Electromyography, upper limb; MR, brachial plexus

© 2001 Lippincott Williams & Wilkins, Inc.