The role of congenital muscular torticollis in the development of deformational plagiocephaly.

Background: Numerous risk factors have been associated with the development of deformational plagiocephaly, although the etiology remains unclear. Torticollis and sternocleidomastoid imbalance are implicated, but reporting is variable. The authors sought to determine the incidence of torticollis/sternocleidomastoid imbalance in deformational plagiocephaly.

Methods: The authors prospectively evaluated 371 infants with cranial asymmetry between 2002 and 2003. Demographic data and medical history were recorded, and a questionnaire was administered. Cranial asymmetry and head rotation were assessed, and variables were statistically analyzed.

Results: Two-hundred two patients were included. Mean age at initial evaluation was 6.1 months (range, 3 to 16 months). Sixty-eight percent (n = 138) were male; 74 percent (n = 149) were flat on the right occiput; 14 percent (n = 28) were from a multiple pregnancy (24 twins, four triplets); 27 percent (n = 54) were premature; and four percent (n = 8) were syndromic. Ninety-three percent (n = 188) of parents did not notice flattening at birth. Ninety-two percent (n = 186) recalled a preferential head position after birth, and in 95 percent of these infants (n = 177 of 186) this improved with age. Only 24 percent (n = 48) of infants had been previously diagnosed or treated for torticollis. Mean cranial asymmetry was 12.5 mm (range, 8 to 25 mm). Ninety-seven percent (n = 195) of infants had head rotational asymmetry of 15 degrees or greater, with more rotation to the flat side. The mean rotational difference was 24 degrees (range 0 to 60; SD 9.8). There was a negative correlation (p = 0.004) between age and head rotational asymmetry (i.e., younger patients exhibited greater asymmetry) and a positive correlation (p = 0.043) between cranial asymmetry and head rotational asymmetry.

Conclusions: The incidence of torticollis/sternocleidomastoid imbalance in deformational plagiocephaly is underreported. Because this condition improves rapidly during early infancy, the findings may be subtle and evidenced only by a history of preferential head rotation. The major cause of deformational plagiocephaly is limited head mobility in early infancy secondary to cervical imbalance.