A rare case of retained medullary cord with sacral subcutaneous meningocele and thoracic arachnoid cyst.

Background: A retained medullary cord (RMC) is an uncommon, closed spinal dysraphism characterized by a robust extended cord-like structure that extends continuously from the conus medullaris to the dural cul-de-sac. There have been six reports of RMC extending to a related sacral subcutaneous meningocele. To the best of authors' knowledge, the combination of retained medullary cord with thoracic arachnoid cyst has never been reported in the literature.

Case presentation: We present a case of the above combination in a 2-year-old child who underwent resection of RMC and fenestration of associated anteriorly placed arachnoid cyst under neuromonitoring. It is prudent to delineate functional and nonfunctional cord segment with neuromonitoring before truncating. The child improved significantly after surgery, and at 1-year follow-up, the child was able to walk with support.

Conclusion: Surgery for RMC involves delineation with neuromonitoring and resection of the nonfunctional cord. Fenestration of the arachnoid cyst must be included in surgical planning, which can be performed as a staged procedure or at same setting.