Accessory brachialis muscle
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- origin: anterior surface of the lower humeral diaphysis
- course: variably medial or lateral to the brachialis muscle
- insertion: variable, including pronator teres or common flexor tendon and proximal radial shaft
- innervation: musculocutaneous nerve or median nerve
Descriptions of origin and course of accessory brachialis muscles have been quite variable. They seem to originate from the anterior lower diaphysis and either medial or lateral intermuscular septum with some reports describing it coursing medially 1-4 and others lateral to the brachialis muscle 5,6.
It might form a fibromuscular tunnel with the intermuscular septum containing the median nerve and the brachial artery 2 continuing into the cubital tunnel together with those neurovascular structures 2-4.
The accessory brachialis muscle might be visualized on imaging studies such as MRI or ultrasound coursing adjacent to the brachialis muscle.
History and etymology
A slip of the brachialis anticus muscle coursing over the brachial vessels and the median nerve had been already described by the British surgeon and anatomist John Wood (1825-1891) in 1867 7,9.
An accessory brachialis muscle might be mistaken for a soft tissue tumor, its knowledge is also helpful in patients undergoing elbow surgery 2.
- 1. Loukas M, Louis R, South G, Alsheik E, Christopherson C. A Case of an Accessory Brachialis Muscle. Clin Anat. 2006;19(6):550-3. doi:10.1002/ca.20285 - Pubmed
- 2. Akhtar M, Fatima N, Kumar S, Kumar B, Kumar V. An Accessory Brachialis Muscle Associated with Abnormal Arrangement of Structures in the Cubital Fossa. Int J Res Med Sci. 2015;3(12):3907-10. doi:10.18203/2320-6012.ijrms20151469
- 3. Vadgaonkar R, Rai R, Ranade A, Nayak S, Pai M, Lakshmi R. A Case Report on Accessory Brachialis Muscle. Rom J Morphol Embryol. 2008;49(4):581-3. - Pubmed
- 4. Paraskevas G, Natsis K, Ioannidis O, Papaziogas B, Kitsoulis P, Spanidou S. Accessory Muscles in the Lower Part of the Anterior Compartment of the Arm That May Entrap Neurovascular Elements. Clin Anat. 2008;21(3):246-51. doi:10.1002/ca.20608 - Pubmed
- 5. Nelluri V, Swamy R, Nayak S, Kumar N, Patil J. Bulky Accessory Brachialis Muscle with Abnormal Aponeurosis: A Case Report. Proceedings of Singapore Healthcare. 2016;25(4):249-251. doi:10.1177/2010105816641698
- 6. Pai M, Nayak S, Vadgaonkar R et al. Accessory Brachialis Muscle: A Case Report. Morphologie. 2008;92(296):47-9. doi:10.1016/j.morpho.2008.04.003 - Pubmed
- 7. Wood J. IV. Variations in Human Myology Observed During the Winter Session of 1866-67 at King's College, London. Proc R Soc Lond. 1867;15:518-46. doi:10.1098/rspl.1866.0119
- 8. Sookur P, Naraghi A, Bleakney R, Jalan R, Chan O, White L. Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation. Radiographics. 2008;28(2):481-99. doi:10.1148/rg.282075064 - Pubmed
- 9. British Medical Journal Publishing Group. John Wood, F.R.S., F.R.C.S. BMJ. 1892;1(1619):96-7. doi:10.1136/bmj.1.1619.96