Ruptured Dermoid Cyst of the Conus Medullaris in the Myelomeningocele Sac Revealed at the Initial Repair Surgery.

Background Dermoid cysts in the myelomeningocele (MMC) site are thought to arise in a delayed fashion because of iatrogenic implantation of dermoid elements at the time of the initial repair surgery. However, there have been few reports on dermoid elements already present at birth. Clinical presentation We report a patient, in whom dermoid cyst was located at dorsal aspect of the conus medullaris in the MMC sac. Between 23 +3 and 24 +4 weeks of gestation, rupture of the MMC sac occurred. At this time of gestation, we speculate that rupture of the dermoid cyst also occurred and dissemination of the cyst contents caused chemical arachnoiditis in the MMC sac. At the age of 1 day, surgery to repair MMC and postoperative histological findings revealed these rare pathologies. Conclusion Physicians should be aware of the possibility of rupture of a dermoid cyst in the MMC sac during fetal period.