Subclavius posticus muscle - an accessory muscle

Case contributed by Dr Matt Skalski

Patient Data

Age: 55
Gender: Male

There is a curvilinear structure that is isointense to muscle on all sequences (however only T1-weighted images are show here), traveling from the superior angle of the scapula to the sternocleidomastoid (SCM) muscle through the posterior cervical space.  This finding is bilateral. 

Annotated image

The accessory muscle is indicated by the blue asterisks.

Case Discussion

The subclavius posticus muscle is a somewhat rare accessory muscle (although on dissection is found in up to 9% - so maybe not so rare), and may occasionally be associated with thoracic outlet syndrome (TOS); however, there is no evidence of TOS in this case. 

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Case information

rID: 30797
Published: 9th Sep 2014
Last edited: 19th May 2020
Inclusion in quiz mode: Included