Fibromatosis colli

Case contributed by Dr Ashesh Ishwarlal Ranchod

Presentation

The patient presents with a non-tender, right-sided, firm neck mass and torticollis.

Patient Data

Age: 6 months
Gender: Female
Ultrasound

There is a distinct, unilateral, fusiform enlargement of the symptomatic right sternocleidomastoid muscle belly. There is no well-circumscribed or delineated intramuscular mass and no calcifications or hemorrhage is present.

The left sternocleidomastoid is normal.

There are incidental predominantly anterior cervical chain, benign, reactive lymph nodes.

Ultrasound

On real-time sonography, there is a synchronous movement of the entire symptomatic sternocleidomastoid muscle. Both the enlarged belly and unaffected muscle fibers blend into each other and move synchronously as demonstrated in the video clips.

Photo

The chin is turned away to the contralateral unaffected side, in this case towards the left.

There is a well visualized focal infra-auricular visible fullness/mass representing the foreshortened left sternocleidomastoid and enlarged muscle belly confirmed on dynamic and static ultrasound examination.

Case Discussion

Fibromatosis colli is also called congenital muscular torticollis, sternocleidomastoid tumor, or pseudotumor of infancy. It is due to the benign fibroblastic proliferation of the affected sternocleidomastoid muscle. The exact pathogenesis is unclear, however, there is an association between fibromatosis colli and birth injury during breech delivery, instrumental delivery, and difficult labor. It has been theorized that during a difficult delivery there is neck compression and resultant ischemic injury or venous occlusion causing damage to the muscle fibers which then undergo fibrosis. Alternatively, there is muscle tearing and hematoma and consequent atrophy and fibrosis.

This case demonstrates typical ultrasound findings of fibromatosis colli in a 6-month-old child. The mum confirmed the identification of the neck "mass" at approximately 6 weeks of age with no progression in size. Recently the infant has had ongoing torticollis and presents with a continuous left-sided chin/facial tilt.

There is a reported incidence of associated skeletal abnormalities, so infants presenting with fibromatosis colli should be examined for the presence of developmental dysplasia of the hip and forefoot.

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