The differential for an intra-dural, extramedullary lesion includes lipoma, epidermoid or dermoid cyst, neurenteric cyst, arachnoid cyst, nerve sheath tumor, meningioma, paraganglioma and metastases. In this case, the lack of high signal suppression on STIR indicates that the lesion is not of fat composition.
The combination of a lesion anterior to the cord and multple segmentation anomalies should strongly suggest a neurenteric cyst, as was histologically proven in this case. The high T1 signal can be ascribed to proteinaceous material within the cyst.
A neurenteric cyst is due to the persistence of the neurenteric canal (canal of Kovalevsky). This results in a potential tract from the mesentery of the gut, passing through malsegmented vertebrae, the spinal canal and cord, through bifid laminae and into the dorsal skin. In practice, the fistula is not fully patent, and a neurenteric cyst is most commonly seen anterior to the cord. At surgery, a fibrous tract to the mediastinum, mesentery or vertebrae may be seen.