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

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 cm3 vs 21.9 ± 22.8 cm3 ; 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 cm3 vs 21.2 ± 23.8 cm3 ; 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.