Transverse plane depiction of the paraspinal muscles included in the measurement at the level of C2/C3. Dorsal group (blue): M. biventer cervicis (1), M. longissimus atlantis et capitis (2), M. complexus (3), M. obliquus capitis caudalis (4); ventral group (red): Mm. intertransversarii (3), M. longus capitis (2), M. longus colli (1).