Sternocleidomastoid ultrasonography data for muscular torticollis in infants

Introduction: This study was performed to obtain normative ultrasonographic data of the sternocleidomastoid (SCM) muscle in infants and to describe an ultrasound method for evaluating muscular torticollis. Methods: The thickness and cross-sectional area (CSA) of the sternal and clavicular heads of the SCM in 84 subjects were analyzed retrospectively. The diagnostic performance of ultrasonography (US) was estimated using receiver-operating characteristic analysis. Results: Muscle thickness increased with age until 10 months. There were no significant differences in thickness or CSA between the right and left sides (P > 0.05) in normal subjects. A ratio of the thickness of the affected side to the unaffected side for the sternal head of the SCM muscle of >1.19 showed a diagnostic sensitivity of 97.9% and specificity of 96.4%. Conclusions: Distinguishing the heads of the SCM muscle and comparing the thickness of the same head on both sides using US may be helpful for evaluating torticollis in infants.