The lemon sign: not a specific indicator of meningomyelocele.

The association of the "lemon sign" with myelomeningocele has been well documented. This study was performed to determine if this sign is exclusive to myelomeningocele. The study population included all abnormal fetuses in our data base with this sonographically observed finding, from 1988 to 1991 (total of 23 cases). Twelve fetuses were found to have a myelomeningocele and six an encephalocele. Five fetuses with the lemon sign demonstrated a variety of structural anomalies not involving the neural tube. This sonographic finding appears not to be limited to cases of myelomeningocele.