Paediatric Imaging

Fibromatosis colli

abnormal enlargement of the sternocleidomastoid muscle developing at 2-8 weeks of life, sometimes with associated torticollis. There are associations with complicated delivery and intrauterine torticollis due to malposition. Clinically a mass or fusiform enlargement of the sternocleidomastoid muscle is found. The mass grows rapidly initially, then stabilises and eventually regresses with no mass palpable after 2 years. Histologically there are atrophic changes in the muscle with partial replacement by fibrous tissue. There is no inflammatory infiltrate.

CT demonstrates focal or diffuse isodense enlargement of the sternocleidomastoid muscle. T2-weighted MRI shows low signal consistent with fibrous tissue and confirms the lack of involvement of surrounding structures. Ultrasound appearances can be variable but usually there is a hyperechoic mass or diffuse sternocleidomastoid enlargement (Fig.1) of mixed echogenicity. Treatment is by physiotherapy.

JC

Fig.1

Fibromatosis colli. Ultrasound demonstrates the enlarged sternocleidomastoid muscle.

Fibromatosis colli, Fig.1