Congenital muscular torticollis: magnetic resonance imaging and ultrasound diagnosis.

The magnetic resonance imaging (MRI) and sonographic appearances of congenital muscular torticollis were studied in a 6-week-old female infant who presented with a firm mass in the right sternocleidomastoid muscle and clinical signs of torticollis. MRI and ultrasound were performed to exclude neoplasm. MRI showed a diffusely enlarged, right sternocleidomastoid muscle that was isointense to normal muscle on T1-weighted conventional spin-echo images. The muscle became progressively brighter and more heterogeneous in signal intensity on proton density- and T2-weighted conventional spin-echo sequences. A thin rim of bright signal intensity on the T2-weighted images surrounded most of the muscle. Ultrasound demonstrated fusi-form enlargement with patchy inhomogeneous areas of increased echogenicity. At 14 weeks there were signs of clinical improvement, with softening of the mass and decreased torticollis.