Fibromatosis Colli

  • Etiology:
    — Birth trauma leads to sternocleidomastoid muscle hemorrhage and pressure necrosis which leads to non-neoplastic fibroblastic proliferation which leads to contracture of sternocleidomastoid muscle
    — In utero compression of sternocleidomastoid muscle
  • Imaging:
    — Right side affected more than left side
    — Purely intramascular lesion
    — Fusiform thickening and shortening of sternocleidomastoid muscle lower half
    — Less commonly seen in trapezius muscle
  • Imaging US:
    — Modality of choice
    — Fusiform on sagittal imaging
    — Early on may appear hypervascular
    — Later on may appear hypovascular and fibrotic
    — Variable echogenicity
    — Calcific foci suggest prior hemorrhage
    — Discrete mass should not be seen
  • DDX:
  • Complications:
  • Treatment: Conservative range of motion therapy
  • Clinical:
    — Presents within 2-8 weeks of delivery as unilateral neck mass
    — 1/3 present with torticollis with chin turned away from affected side
    — More common in breech presentation and forceps delivery

Radiology Cases of Fibromatosis Colli

CT and US of fibromatosis coli / torticollis tumor
Axial CT with contrast of the chest (above) shows asymmetry of the sternocleidomastoid muscles, right larger than left. Transverse US of the chest (middle) at the same level of the CT better shows the enlarged right sternocleidomastoid muscle. Sagittal US of the sternocleidomastoid muscles (bottom) shows the normal smooth contour of the left sternocleidomastoid muscle and the spindle shaped appearance of the right sternocleidomastoid muscle.
US of fibromatosis coli
Transverse US of the neck shows a normal sized hyopechoic left sternocleidomastoid muscle lying above the jugular vein and carotid artery. The right sternocleidomastoid muscle is more heterogenous in echotexture and is 3-4 times larger in size than the left.
US of fibromatosis coli
Transverse US of the neck shows a normal sized hypoechoic right sternocleidomastoid muscle lying above the jugular vein and carotid artery. The left sternocleidomastoid muscle has a heterogenous echotexture and is 5-6 times larger in size than the right.