Difference of accessory nerve size between infants with postural torticollis and congenital muscular torticollis

Abstract

Purpose To investigate the upper trapezius muscle thickness (UTMT) using ultrasound (US) in infants with congenital muscular torticollis (CMT) and correlation among sternocleidomatoid muscle thickness (SCMT), accessory nerve (AN) and UTMT in CMT. Method The study recruited 17 infants with the difference of the thickness of the SCM muscle on both sides greater than 2 mm on ultrasonography (group 1-CMT) and 21 infants with the difference of the thickness of the SCM muscle on both sides less than 2 mm (group 2-postural torticollis (PS)). A physiatrist performed B-mode US measured the SCMT, UTMT, and calculated the cross-sectional area (CSA) of the AN in both groups (Figure 1). We calculated SCMT, UTMT, and AN ratio (affected/unaffected thickness) in both groups. We also evaluated the correlation among sternocleidomatoid muscle thickness (SCMT), CSA of AN and UTMT in both groups. Result SCMT, UTMT, and CSA of the AN in affected side in group 1 was significantly greater than that in group 2 (Table 1). SCMT, UTMT, and CSA of the AN in affected side was significantly greater than that in unaffected side in group 1. However, there was no significant differences in group 2 (Table 2). CSA of the AN in affected side in group 1 was positively correlated with UTMT (r = 0.55, Table 3) and not with SCMT. There was no correlation among SCMT, UTMT, and CSA of the AN in affected side in group 2. Conclusion This study demonstrated that SCM size affect upper trapezius muscle thickness via different accessory nerve size in infants with congenital torticollis.