THE DIFFERENTIAL-DIAGNOSIS OF POSTERIOR PLAGIOCEPHALY - TRUE LAMBDOIDSYNOSTOSIS VERSUS POSITIONAL MOLDING

The diagnosis and treatment of posterior plagiocephaly is one of the m ost controversial aspects of craniofacial surgery. The features of tru e lambdoid synostosis versus those of deformational plagiocephaly seco ndary to positional molding are inadequately described in the literatu re and poorly understood. This has resulted in many infants in several craniofacial centers across the United States undergoing major intrac ranial procedures for non-synostotic plagiocephaly. The purpose of thi s study was to describe the detailed clinical, imaging, and operative features of true lambdoid synostosis and contrast them with the featur es of positional plagiocephaly. During a 4-year period from 1991 to 19 94, 102 patients with posterior plagiocephaly were assessed in a large multidisciplinary craniofacial program. During the same period, 130 p atients with craniosynostosis received surgical treatment. All patient s were examined by a pediatric dysmorphologist, craniofacial surgeon, and pediatric neurosurgeon. Diagnostic imaging was performed where ind icated. Patients diagnosed with lambdoid synostosis and severe and pro gressive positional molding underwent surgical correction using standa rd craniofacial techniques. Only 4 patients manifested the clinical, i maging, and operative features of unilambdoid synostosis, giving an in cidence among all cases of craniosynostosis of 3.1 percent. Only 3 amo ng the 98 patients with positional molding required surgical intervent ion. All the patients with unilambdoid synostosis had a thick ridge ov er the fused suture, identical to that found in other forms of cranios ynostosis, with compensatory contralateral parietal and frontal bossin g and an ipsilateral occipitomastoid bulge. The skull base had an ipsi lateral inferior tilt, with a corresponding inferior and posterior dis placement of the ipsilateral ear. These characteristics were completel y opposite to the findings in the 98 patients who had positional moldi ng with open lambdoid sutures and prove conclusively that true unilamb doid synostosis exists as a specific but rare entity. Awareness of the features of unilambdoid synostosis will allow more accurate diagnosis and appropriate treatment of posterior plagiocephaly in general and i n particular will avoid unnecessary surgical intervention in patients with positional molding.