Occipital plagiocephaly: Deformation or lambdoid synostosis: I. morphometric analysis and results of unilateral lambdoid craniectomy

Between 1987 and 1992, 30 infants aged 1.4-13 months (mean 7.3 months) underwent unilateral lambdoid strip craniectomy at the Children’s Hospital of Buffalo for occipital plagiocephaly. Males outnumbered females (22:8) and right-sided occipital flattening was significantly more common than left-sided flattening (25:5). The deformity was noticed at an average age of 3.2 months; 16% of the infants had an asymmetry at birth. Positional preferences (a distinct tendency to lie preferentially on the back, in most cases with the head turned to the ipsilateral side) were described in 79% of infants for whom this information was available, and torticollis was present in 10%. Pre- and postoperative CT scans were analyzed using several morphometric measurements. Asymmetries were measured between the flattened and contralateral sides, both posteriorly and anteriorly, using a translucent grid placed over the CT slice showing maximum asymmetry. The average maximum asymmetry between the flattened and contralateral sides was 24% posteriorly and 16% anteriorly. Significant improvements were seen postoperatively, with both anterior and posterior asymmetries improving by an average of one third (p < 0.05). However, when compared with CT scans from a control group of infants without synostosis, the operated group showed persistent and significant asymmetries postoperatively. The morphometric measurements described allow an objective and reproducible means of assessing the results of various treatments for this disorder. The improvements following unilateral lambdoid craniectomy are difficult to interpret in isolation; we suggest that future efforts be directed toward similarly assessing the results of both nonoperative treatments such as positional changes and molding helmets, and more aggressive surgical treatments that have been advocated for this disorder.