Cloverleaf skulls: etiologic heterogeneity and pathogenetic variability.

Cloverleaf skulls (Kleeblattschädel-Syndromen, trilobular skulls) have different modes of development (pathogenetic variability). Synostosis may involve various sutures in different types of cloverleaf skulls. Their facial features, radiographic findings, and CNS anomalies are also reviewed. Different causes of cloverleaf skulls have been identified (etiologic heterogeneity). One table lists 26 different conditions with trilobular skulls identified under various etiologic headings: monogenic, chromosomal, disruptive, iatrogenic, and distinctive conditions of unknown cause. Discussed in detail are type 2 thanatophoric dysplasia, type 2 Pfeiffer syndrome, Apert syndrome, amniotic bands, Say-Poznanski syndrome, and COH syndrome. Another table summarizes the relative frequencies of the cloverleaf skull syndromes.