Background: Congenital muscular torticollis (CMT) in infancy is caused by the fibrotic change of the sternocleidomastoid muscle (SCMM). The etiology and management strategies remain controversial.
Methods: One hundred ninety-seven infants and children aged 1 month to 16 years who had CMT were examined by real-time ultrasonography of the SCMM between June 1995 and September 1996 in a prospective and longitudinal study. A total of 362 examinations were performed. There were 122 boys and 75 girls.
Results: The right side was involved in 117 patients (59.3%), the left side in 79 patients (40.1%), and both sides in one patient. The sonographic findings were homogeneous or heterogeneous (patchy) hyperechoic lesion within the SCMM, and all were diagnostic. The ultrasonographic appearance of the SCMM in this study has a close resemblance to the clinical course of CMT. The extent of fibrosis as represented by the cross section of lesion to muscle ratio (L/M ratio) decreased from 83.6% at 2 months to 59.9% at 9 months of age and further decreased to 40% beyond 1 year of age. This consistent decrease in fibrosis was caused by the increased normal muscle volume at the periphery and by the regenerated muscle fibers within the lesion. In this series of 197 patients, 32 (16.2%) eventually underwent surgery to release the SCMM because of persistent head tilt, chin deviation and limited range of neck motion beyond 1 year of age. The L/M ratio of the operative group was 62.7 +/- 16.0% compared with an L/M ratio of 54.5 +/- 14.2% (P = .035) for the nonoperative group at 1 year of age. The extent of fibrotic change in the cross section of the muscle was a significant factor in determining prognosis. In the longitudinal section, the fibrotic change was limited to only the lower third of the SCMM in 27 patients, and all of them recovered without operation. In 95 patients, the fibrotic lesion was limited to the middle and lower third or middle third only, and only six (6.3%) underwent operation. However, in 75 cases the entire length of muscle was involved, and 26 (34.7%) required surgical release of the contracted muscle. Whole-length muscle involvement was also important for predicting recovery without operative intervention.
Conclusions: Ultrasonographic study of the SCMM is not only a valuable diagnostic tool but can also serve as a useful guideline for the treatment of infants who have congenital muscular torticollis.