Radiology quiz

aFall 2001

A 3 ½-week-old healthy male infant presented with a right neck mass. This boy had been delivered vaginally at term; pregnancy and delivery were uncomplicated. On exam, the boy had a 2-cm, firm, well-circumscribed mass palpable in the right neck, above the medial right clavicle. The mass was superficial but not fixed to skin. Tenderness was difficult to determine as he became irritable when the neck was manipulated. The infant's head was held tilted toward the right and the chin was directed to the left. The right occiput was flattened. An ultrasound study of the neck showed a fusiform enlargement of the sternocleidomastoid (SCM) muscle with heterogeneous echogenicity (Figure 1).

What is the diagnosis?

Answer:  Sternocleidomastoid pseudotumor of infancy, or fibromatosis colli (Figure 2).

Follow-up:  The parents began passive range of motion exercises, rotating the infant's head fully to each side with several repetitions, 4 to 5 times daily. The infant was held and positioned to encourage active rotation to look to the right side. At a 6-month follow-up visit, the mass had disappeared. Head position and tracking were normal. The cranial outline was symmetrical.

Discussion:  The differential diagnosis of neck masses in infancy includes infection, congenital cysts, neoplasm, or traumatic lesions. The sternocleidomastoid tumor of infancy, or fibromatosis colli, is a localized fibrous tissue mass within the sternocleidomastoid (SCM) muscle. An ipsilateral head tilt and contralateral chin rotation commonly occur, giving rise to the popular connotation—"torticollis." Fetal intrauterine malposition, birth trauma, or vascular compromise has been proposed as possible etiologies for this benign, self-limited condition. Associated problems may include congenital hip dysplasia, clubfoot, and Erb's palsy.[1]

The lateral neck mass commonly is noted by a parent at 4 to 6 weeks of age and occurs with equal frequency on the right and left sides of the neck. The diagnosis of fibromatosis colli often can be made on the basis of a thorough history and physical exam. However, additional studies may be helpful to confirm the clinician's impression. We advocate ultrasound as the adjunctive study of choice in infants with this suspected pseudotumor.[2] Ultrasonography is a noninvasive study that is relatively inexpensive and provides highly specific imaging for this condition. This modality can be performed without the need for sedation and avoids exposure to ionizing radiation. In these cases, the ultrasound demonstrates a mass within the mid to lower sternocleidomastoid muscle with an equal frequency of heterogeneous or homogeneous characteristics (Figure 1).[3] Synchronous movement of the mass with the muscle is seen with real time sonography.[4]

The mass of fibromatosis colli disappears by 6 to 8 months of age in 80% of cases. Five to 20% of patients may develop true muscular torticollis.[5,6] Treatment is conservative and includes passive and active range of motion exercises to prevent contracture and permanent shortening of the SCM muscle.[7] Uncorrected rotation and tilting of the head will lead to permanent fibrosis and contraction of the SCM muscle with progressive craniofacial growth asymmetry (nonsynostotic positional plagiocephaly)—hence the urgency for prompt and appropriate intervention.[8] In such cases, surgical release may be necessary.

REFERENCES

1.  Tom LWC, Handler SD, Wetmore RF, Potsic WP: The sternocleidomastoid tumor of infancy. Int J Pediatr Otorhinolaryngol 1987;13:245–255.

2.  Maddalozzo JM, Goldenberg JD: Pseudotumor of infancy—the role of ultrasonography. Ear Nose Throat J 1996;75:248–254.

3.  Chan FA, Altenberg A: Congenital muscular torticollis. J Am Med Assoc 1944;125:476–483.

4.  Kraus R, Han BK, Babcock DS, Oestreich AE: Sonography of neck masses in children. Am J Rheumatol 1986;146:609–613.

5.  Hulbert KF. Congenital torticollis. J Bone Joint Surg (Br) 1995;32: 50–59.

6.  Coventry MB, Harris LE: Congenital muscular torticollis of infancy. J Bone Joint Surg (Am) 1959;41:815–822.

7.  Cheng JCY, Tang SP, Chen TMK, Wong MWN, Wong EMC. The clinical presentation and outcome of treatment of congenital muscular torticollis in infants—a study of 1,086 cases. J Pediatr Surg 2000;35:1091–1096.

8.  Demerbile S, Atayurt HF. Congenital muscular torticollis and sternomastoid tumor: results of nonoperative trteatment. J Pediatr Surg 1999;32:549–551.

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