Congenital Dermal Sinus Elements in Each Tethering Stalk of Coexisting Thoracic Limited Dorsal Myeloschisis and Retained Medullary Cord

Abstract

<b><i>Introduction:</i></b> The embryogenesis of limited dorsal myeloschisis (LDM) likely involves impaired disjunction between the cutaneous and neural ectoderms during primary neurulation. Because LDM and congenital dermal sinus (CDS) have a shared origin in this regard, CDS elements can be found in the LDM stalk. Retained medullary cord (RMC) is a closed spinal dysraphism involving a robust, elongated, cord-like structure extending from the conus medullaris to the dural cul-de-sac. Because the RMC is assumed to be caused by impaired secondary neurulation, concurrent RMC and CDS cannot be explained embryologically. In the present article, we report a case in which CDS elements were noted in each tethering stalk of a coexisting LDM and RMC. <b><i>Case Presentation:</i></b> A 2.5-month-old boy with left clubfoot and frequent urinary and fecal leakage had 2 tethering tracts. The upper tract, which ran from the thoracic tail-like cutaneous appendage, had CDS elements in the extradural stalk and a tiny dermoid cyst in the intradural stalk immediately after the dural entry. In the lower tract, which ran from the lumbosacral dimple, the CDS as an extradural stalk continued to the RMC at the dural cul-de-sac. Both stalks were entirely resected through skip laminotomy/laminectomy at 1 stage to untether the cord and resect the CDS elements. <b><i>Conclusion:</i></b> Surgeons should be aware that CDS elements, in addition to LDM, may coexist with RMC that extends out to the extradural space.

Surgical histopathology of a filar anomaly as an additional tethering element associated with closed spinal dysraphism of primary neurulation failure

“…In Patient 6, there was no E-LC but NGT. We think that small islands of E-LC may have been missed during routine sectioning of the surgical specimen, as were described elsewhere;[ 9 ] hence, it was determined to be positive E-LC w/NGT. Thus, E-LC w/ NGT was noted in 8 (66.7%) out of 10 fila, including C-LSs.…”

“…In cases of suspected RMC, the border between the true cord and nonfunctional C-LS was determined by tracing the evoked CMAPs by stimulation in the rostrocaudal direction, beginning from the functional cord, and proceeding to the nonfunctional C-LS, as described previously. [ 9 , 10 ]…”

“…The detailed clinicopathological findings of LDM in Patients 6-10 have been described before [ Table 2 ]. [ 6 , 9 , 12 - 14 ]…”

“…[ 7 , 10 , 18 , 20 , 21 , 25 ] As a nonfunctional RMC is indistinguishable from the functional conus on neuroimaging and in the intraoperative view, confirmation of the presence of a nonfunctional C-LS with intraoperative neurophysiological monitoring (IONM) is essential for the diagnosis of RMC. [ 7 , 9 , 10 , 20 , 21 , 23 ] Histopathology of the C-LS resected at surgery typically shows a central canal-like, ependyma-lined canal with surrounding neuroglial tissues (E-LC w/NGT), corroborating the picture of a remnant of the cavitary medullary cord, which is normally regressed but can remain due to late arrest of secondary neurulation before the degenerative phase. [ 20 , 21 ]…”

“…When there are alterations present in both the primary and secondary neurulation, we can find the coexistence of dysraphism that presents with elements from the two forms of neural tube defects. [ 8 , 9 , 15 , 21 ] While Gupta and Rajshekhar[ 4 ] stressed that closed spinal dysraphism of primary neurulation failure could be associated with filar anomalies, such as filar lipoma (or fatty filum) or TFT, resulting from impaired secondary neurulation, as an additional tethering element, detailed histopathological findings have not been fully demonstrated. Our previous report demonstrated that some filar lipomas also contain E-LC w/NGT, which is the characteristic histopathology of the C-LS of RMC.…”