Detection of open spina bifida by the lemon sign: pathologic correlation.

This study was undertaken to evaluate the association of medial displacement of the frontal bones of the fetal calvarium, the lemon sign, with open spina bifida (OSB) and to assess other pathologic findings associated with this change. During the past 8 years, 8 cases of OSB were seen in our institution. The lemon sign was retrospectively identified in 6/6 cases of OSB scanned before 22 weeks gestation, while it was not seen in 3/3 cases examined after 26 weeks. One case was evaluated with serial studies before and after 22 weeks. Scalloping of the frontal bones was associated with a wide variety of pathological findings. This sign may prove to be an important marker for OSB.