Axial CT with contrast of the chest (above) shows asymmetry of the sternocleidomastoid muscles, right larger than left. Transverse US of the chest (middle) at the same level of the CT better shows the enlarged right sternocleidomastoid muscle. Sagittal US of the sternocleidomastoid muscles (bottom) shows the normal smooth contour of the left sternocleidomastoid muscle and the spindle shaped appearance of the right sternocleidomastoid muscle.
Pediatric Imaging 