The cloverleaf skull anomaly: an anatomic and histologic study of two specimens.

Two neonatal human specimens exhibiting the cloverleaf skull anomaly were studied in detail using gross, radiographic and histologic techniques. Both specimens exhibited premature fusion of the right and left coronal sutures, right and left lambdoidal sutures, and midsagittal sutures. Although the specimens grossly exhibited a similar trilobed appearance of the craniofacial complex, the interrelationship and spatial orientation of their respective articular and skeletal components differed markedly. The development of the cranial base in one specimen appeared normal, while in the other specimen, the synchondroses between the supraoccipital, exoccipital, basioccipital, basisphenoid, and presphenoid bones were prematurely obliterated histologically, resulting in a substantial decrease in the length of the cranial floor. The latter specimen also exhibited micromelic shortening of the limbs with abnormal chondrocyte proliferation and maturation at the epiphyseal growth plates. The alterations in the size and shape of the calvarial bones subsequent to premature sutural synostosis were more severe in the specimen with premature closure of the cranial base synchondroses. The striking differences observed in the anatomic and histologic analysis of the specimens demonstrated tha the cloverleaf skull malformation must be etiologically and pathogenetically heterogeneous.