P.S : the lower part of the trapezius ( shoulder region itself ), receives some supply from the cervical plexus and hence is relatively spared.
one more differential according to my friend, Emik ( an orthopedic ) is supraspinatus tendon injury, followed by atrophy.
I would like to see his SCM but it appears his trapezius is atrophied - possible accessory nerve palsy
I am putting forth another strong differential - AXILLARY NERVE INJURY. It's very subtle, but i looked carefully and noticed a slight drooping of the right shoulder and what we are seeing as trapezius atrophy, may well be deltoid atrophy. Another possibility is C4, C5 nerve root damage - which could affect the levator scapulae ( but that doesn't seem to be the case from this image. )
Now, that i know the entire story - it's a case of axillary nerve injury, leading to deltoid atrophy on the left side. @ Egyptian Doctor - Bro, this was really hard :ambivalence: same guy front on ( taken at the same time as above ) and even from this image it would be hard to pick, becos most rt. dominant people will have slightly bigger muscles on the right side. Read entire story here - Very interesting case of Axillary nerve damage in a 22-year-old rugby player « Functional Anatomy Seminars – Functional Anatomic Palpation Systems
