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. 2007 Jun 23:2:14.
doi: 10.1186/1749-7221-2-14.

Variations of the origin of collateral branches emerging from the posterior aspect of the brachial plexus

Luis Ernesto Ballesteros  1 , Luis Miguel Ramirez
Affiliations

Variations of the origin of collateral branches emerging from the posterior aspect of the brachial plexus

Luis Ernesto Ballesteros et al. J Brachial Plex Peripher Nerve Inj. .

Abstract

Background: The frequency of variation found in the arrangement and distribution of the branches in the brachial plexus, make this anatomical region extremely complicated. The medical concerns involved with these variations include anesthetic blocks, surgical approaches, interpreting tumor or traumatic nervous compressions having unexplained clinical symptoms (sensory loss, pain, wakefulness and paresis), and the possibility of these structures becoming compromised. The clinical importance of these variations is discussed in the light of their differential origins.

Methods: The anatomy of brachial plexus structures from 46 male and 11 female cadaverous specimens were studied. The 40-80 year-old specimens were obtained from the Universidad Industrial de Santander's Medical Faculty's Anatomy Department (dissection laboratory). Parametric measures were used for calculating results.

Results: Almost half (47.1%) of the evaluated plexuses had collateral variations. Subscapular nerves were the most varied structure, including the presence of a novel accessory nerve. Long thoracic nerve variations were present, as were the absence of C5 or C7 involvement, and late C7 union with C5-C6.

Conclusion: Further studies are needed to confirm the existence of these variations in a larger sample of cadaver specimens.

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Figures

Figure 1
Figure 1
Right BP with collateral origin variations for upper subscapular nerve and an accessory subscapular nerve. C5, C6, C7, C8, T1: spinal nerve ventral rami. ST: superior trunk. MT: middle trunk. IT: inferior trunk. LC: lateral cord. PC: posterior cord. MC: medial cord. A: axillary nerve. R: radial nerve. Mct: musculocutaneous nerve. U: ulnar nerve. M(LH): lateral head of median nerve. M(MH): medial head of median nerve. PM: pectoralis minor muscle. SSM: subscapularis muscle. DM: deltoid muscle. 1: dorsal scapular nerve.2: suprascapular nerve. 3: upper subscapular nerve (originating from the ST posterior cord). 4: accessory subscapular nerve. 5: lower subscapular nerve. 6: long thoracic nerve.
Figure 2
Figure 2
Right BP with collateral origin variations for lower subscapular nerve and thoracodorsal nerve. C4, C5, C6, C7, C8, T1, T2: spinal nerve ventral rami with prefixed C4 (asterisk) and postfixed T2 (asterisk). ST: superior trunk. MT: middle trunk. IT: inferior trunk. LC: lateral cord. PC: posterior cord. MC: medial cord. A: axillary nerve. R: radial nerve. Mct: musculocutaneous nerve. U: ulnar nerve. M: median nerve. ASM: serratus anterior muscle. SSM: subscapularis muscle. CP: cervical plexus. 1: dorsal scapular nerve (originating from C4). 2: suprascapular nerve. 3: upper subscapular nerve. 4: lower subscapular nerve (originating from the axillary nerve). 5: thoracodorsal nerve originating from MT posterior division. 6: long thoracic nerve.
Figure 3
Figure 3
Left BP with collateral origin variations for shared C5. C5, C6, C7, C8, T1: spinal nerve ventral rami. AA: axillary artery. LSM: levator scapula muscle. SSM: subscapular muscle. ASM: anterior serratus muscle. A: axillary nerve. R: radial nerve. U: ulnar nerve. M: median nerve.1: dorsal scapular nerve. 2: ramus from C5 to long thoracic (sharing the same root with dorsal scapular). 3: C6 ramus to long thoracic. 4: suprascapular nerve. 5: upper subscapular nerve. 6: lower subscapular nerve. 7: thoracodorsal nerve. 8: long thoracic nerve.
Figure 4
Figure 4
Left BP with collateral origin variations for subscapular nerves. C5, C6, C7, C8, T1: spinal nerve ventral rami. ST: superior trunk. MT: middle trunk. IT: inferior trunk. LC: lateral cord. PC: posterior cord. MC: medial cord. A: axillary nerve. R: radial nerve. Mct: musculocutaneous nerve. U: ulnar nerve. M: median nerve. ASM: serratus anterior muscle. SSM: subscapularis muscle. PMM: pectoralis minor muscle. 1. suprascapular nerve. 2: upper subscapular nerve (originating from the ST posterior cord). 3: accessory subscapular nerve. 4. lower subscapular nerve (originating from the thoracodorsal nerve). 5: long thoracic nerve. 6: dorsal scapular nerve (originating from C4).
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