From a series of 1,833 patients with craniosynostosis, 278 cases with metopic synostosis were analysed. The prevalence of metopic synostosis was estimated in the region of 1 in 15,000 children.
Patients and methods: All patients with metopic suture fusion were selected, excluding cases where additional sutures were involved. The age at diagnosis was between 15 days and 15 years. The diagnosis was based on clinical and radiological evaluation. The search for associated malformations was based on clinical evaluation, CT or MRI scans, bone X-rays and ultrasounds. If possible, a study of the karyotype was performed in case of associated malformation. Family information was obtained through contact with the families, generally in person or sometimes by telephone. The series was divided into three groups: isolated trigonocephaly (group 1), trigonocephaly associated with other malformations without any known syndrome (group 2) and well delineated syndromes (group 3).
Results: There were 213 males and 65 females, a sex ratio of 3.3. Family information was obtained from 222 probands distributed among 216 families. There was no maternal or paternal age effect. The frequency of twinning was 7.9%, with three concordances for metopic synostosis in three monozygotic twin pairs. A positive family history was obtained in 13 of the 216 pedigrees, giving a 6% figure of familial cases. A vertical transmission was observed in only one case; in all other cases, there were two affected children with normal parents. Eleven familial cases were isolated trigonocephalies, and two were syndromic. Nine of the 53 available karyotypes were abnormal, involving the chromosomes 7, 9, 11 or 13. There were 208 observations in the group 1. In 53 cases (group 2), associated malformations involved mainly the heart (12 cases), the limbs (six cases), the brain (five cases) and the genito-urinary tract (four cases). These malformations were unique in 32 cases and multiple in 21 cases. Some: of the observations could represent new syndromes. Seventeen syndromes represented group 3. Nine were chromosomal syndromes. Eleven presented with multiple malformations. An in utero exposure to valproic acid was observed in two cases of the group 1, five cases of the group 2 and one case of the group 3.