Age / Sex : 61 / M

Chief complaint : Left medial elbow pain for 2 years


What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).


Courtesy : 김완태 ( Wan Tae Kim ), 중앙보훈병원 ( Veterans Health Service Medical Center )

Anconeus epitrochlearis (Accessory muscle)

Discussion

Findings:

Axial and coronal MR images shows well demarcated soft tissue mass like lesion of isointense signal intensities compared with the skeletal muscles, superficial to the cubital tunnel.

Diagnosis:  

Anconeus epitrochlearis (Accessory muscle)

Discussion:

Anconeus epitrochlearis muscle is a congenial accessory muscle that originates from the medial humeral epicondyle and attaches to the medial side of the olecranon. It is also known as the accessory anconeus muscle or epitrochleoanconeus muscle and should not be confused with the anconeus muscle which is present at the lateral aspect of the elbow.

The prevalence has ranged from 4% to 34% in cadaveric studies. The anconeus epitrochlearis muscle is usually seen bilaterally.

It can be asymptomatic or symptomatic when there is compression of the ulnar nerve within the cubital tunnel, leading to ulnar neuritis.

References:

1. Morgenstein A, Lourie G, Miller B. Anconeus epitrochlearis muscle causing dynamic cubital tunnel syndrome: a case series. J Hand Surg Eur Vol. 2016 Feb;41(2):227-229.


2. Stein JM, Cook TS, Simonson S et al. Normal and variant anatomy of the elbow on magnetic resonance imaging. Magn Reson Imaging Clin N Am. 2011;19(3):609-619.


3. Sookur PA, Naraghi AM, Bleakney RR et al. Accessory muscles: anatomy, symptoms, and radiologic evaluation. Radiographics. 2008;28(2):481-499.