Ipsilateral Hypertrophy of the Mastoid Process in Surgical Cases of Congenital Muscular Torticollis

Abstract

OBJECTIVE: This study was to investigate ipsilateral hypertrophy of the mastoid process in the patients with congenital muscular torticollis (CMT). DESIGN: Retrospective cross-sectional study. PATIENTS: Children with CMT. METHODS: A total of 212 surgical cases of patients with CMT (age: 50.9 +/- 44.3 months) and 212 age- and gender-matched controls (age: 50.4 +/- 44.2 months) were included. The mastoid process volume was calculated and compared for both groups on the computed tomography axial images. A linear regression analysis was performed between the age and the intrasubject volume difference in the mastoid process. RESULTS: The volume of the mastoid process in the CMT side was significantly larger than that of the non-CMT side in the CMT group (32.2 +/- 30.3 cm(3) vs 21.9 +/- 22.8 cm(3): P < .001). In the control group, there was no significant difference between the volume of the right and left mastoid process (21.6 +/- 24.6 cm(3) vs 21.2 +/- 23.8 cm(3): P = .472). The intrasubject volume difference in the mastoid process in the CMT group showed a linear increase with the age (adjusted R (2) = 0.286: P < .001), and the volumetric asymmetry of the mastoid process became more severe over age compared to the control group. CONCLUSION: We showed ipsilateral hypertrophy of the mastoid process in patients with CMT and demonstrated that the volumetric asymmetry increased with age.