retained medullary cord
A rare closed dysraphism with terminal stalk characterized by persistent rudimentary spinal cord below conus. It contains non-functional neural tissue and is typically isolated. The diagnostic is suggested by attenuated conus without fat, further confirmed by pathological analysis (glioneuronal core with ependyma-lined lumen, nerve roots, and dorsal root ganglia). Differential diagnostic with intraoperative neurophysiological monitoring is mandatory as neuroimaging fails to distinguish it from functional conus.