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. 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. 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.

Omphalocele-exstrophy-imperforate anus-spinal defects (OEIS) complex is a rare, life-threatening congenital malformation primarily treated with abdominogenital repair. The optimal indication and timing of neurosurgical interventions for the associated spinal cord lesions remains insufficiently studied. We reviewed spinal dysraphism in OEIS to evaluate the best timing for neurosurgical intervention. We retrospectively reviewed 10 patients with OEIS, analyzing their clinical and imaging data, as well as surgical and pathological findings. Terminal myelocystocele (TMCC) and spinal lipomas were observed in 5 patients each. Of the spinal lipomas, one had a single filar lipoma, while four had double lipomas (3 caudal and dorsal; 1 filar and dorsal). TMCC manifested with severe lower limb motor dysfunction in addition to abdominogenital disorder at birth, with the cyst-induced lumbosacral mass increasing over time. Spinal lipomas were less symptomatic except for abdominogenital issues and demonstrated minimal growth of the intraspinal lipoma over time. Untethering surgery was performed in 8 patients (5 TMCC; 3 spinal lipomas) at a median age of 3 (range, 2-10) months for TMCC and 6 (range, 2-14) months for spinal lipomas. One TMCC patient (surgery at 10 months) experienced postoperative cerebrospinal fluid leakage, necessitating three reoperations. Magnetic resonance imaging is essential to diagnose spinal cord malformations accurately. The necessity and timing of surgical intervention differ between TMCC and spinal lipomas. Since TMCC lesions tend to enlarge, surgery should be performed as soon as the patient's abdominogenital condition stabilizes. For spinal lipomas, surgery should be considered carefully based on the patient's neurological condition.

Retained medullary cord (RMC) and filar lipomas are believed to originate from secondary neurulation failure; filar lipomas are reported to histopathologically contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissue with ependyma-lined central canal (NGT w/E-LC) as a remnant of the medullary cord, which is a characteristic histopathology of RMC. With the addition of glial fibrillary acidic protein (GFAP) immunostaining, we reported the presence of GFAP-positive NGT without E-LCs (NGT w/o E-LCs) in RMC and filar lipomas, and we believe that both have the same embryopathological significance. We examined the frequency of GFAP-positive NGT, with or without E-LC, in 91 patients with filar lipoma. Eight patients (8.8%) had NGT w/E-LC, 25 patients (27.5%) had NGT w/o E-LC, and 18 patients (19.8%) had tiny NGT w/o E-LC that could only be identified by GFAP immunostaining. Combining these subgroups, 56% of the patients (n = 51) with filar lipoma had GFAP immunopositive NGT. The fact that more than half of filar lipomas have NGT provides further evidence that filar lipoma and RMC can be considered consequences of a continuum of regression failure that occurs during late secondary neurulation.

Retained medullary cord (RMC) is a recently defined term denoting closed spinal dysraphism arising from the failure of regression in secondary neurulation. Despite the acknowledgment of this condition, there needs to be more literature elucidating the radiologic manifestations of RMC. This study aimed to describe the MR imaging findings of RMC. A retrospective analysis was conducted on spinal MRI scans of pediatric patients with surgically confirmed RMC, from January 2014 to August 2023. The investigation focused on evaluating the following image characteristics: level and morphology of the cord-like structure (C-LS), the signal intensity in the far distal C-LS, nerve root-like structures originating from the C-LS, intradural fatty lesions, and arachnoid cysts. This study included 38 patients (19 girls, mean age 7.3 months) who showed a low-lying cord in all cases. The morphology of C-LS was either smooth tapered (50%) or hourglass with fusiform cystic dilatation (50%). The C-LS exhibited aberrant T2 hypointense signal compared to the juxta-proximal level. T2 hypointense signal vestigial nerves emanating from the C-LS and intradural fatty masses were observed (89.5%). Sacral arachnoid cysts in extradural location were identified in eight patients. The characteristic MR features of RMC revealed an extremely low-lying distal C-LS with smooth tapering or hourglass-shaped cystic dilatation of the caudal part, accompanied by an intradural fatty stalk and the aberrant signal vestigial nerve. This study suggests those radiologic findings can be RMC instead of the previously called terminal syrinx with low-lying conus.

Intramedullary spinal capillary hemangioma is a rare occurrence in pediatric patients, and only limited cases have been reported. This study presents the first two cases of spinal capillary hemangioma co-present with retained medullary cord and one case of spinal capillary hemangioma with lumbosacral lipomatous malformation. Previous literature on ten patients with this pathology was reviewed. We speculated pathogenesis, imaging features, and histopathologic findings of the disease.