Eur J Anat, 21 (1): 71-75 (2017)

Unilateral absence of ascending and transverse trapezius fibers accompanied by mild thoracic scoliosis: a case report

Rosa S. Valtanen¹, Aaron Z. Katrikh², Alessandra Y. Chen¹, M. Elena Stark²

¹David Geffen School of Medicine at UCLA, ²David Geffen School of Medicine at UCLA, Department of Pathology and Laboratory Medicine, Division of Anatomy, Los Angeles, USA

ABSTRACT During routine anatomical dissection at the David Geffen School of Medicine at UCLA, a variation of partial unilateral trapezius muscle absence was found in a 95-year-old Caucasian female. A broad sheet of aponeurosis originating from all thoracic vertebrae completely replaced the ascending fibers of the left inferior trapezius muscle. Transverse fibers of the left trapezius muscle appeared hypotrophied and were sparsely distributed within the aponeurosis. Descending fibers of the left trapezius muscle were comparable to the right side. The main clinical finding was a grossly visible 5-degree thoracic scoliosis toward the intact trapezius muscle. No other significant abnormalities in musculature or anatomy could be found. While others have reported on unilateral, bilateral, complete, and partial absence of trapezius muscle, to our knowledge this case is unique from those previously reported in the literature.

Keywords: Partial absence of trapezius muscle â?? Hypoplastic trapezius muscle - Underdeveloped trapezius muscle â?? Mild thoracic scoliosis