Type 1.5 split cord malformation

Type 1.5 split cord malformation

A subtype of split cord malformation with combined characteristics of types I and II.

A 11-year-old male child, presented with low backache after trivial trauma. He was neurologically intact. Imaging revealed low lying tethered cord and a midline ventral bony spur (D12, L1) with a single dural sac encasing both the hemi cords. Surgical exploration revealed a ventral bony spur with two hemicords, enclosed in a single dural tube. Excision of the bony spur and detethering of the filum terminal was done. Post-operative course was uneventful and the patient was discharged satisfactorily.

SCMs possibly represent, a continuum of changes beginning at the gestational age of day 20-30. Terminologies like mixed or intermediate type, are used to denote SCMs that showed features of both type 1 and type II.

Meena et al. prefered using type “1.5 SCMs” for all such cases, thereby avoiding confusion and maintaining uniformity in nomenclature. However, further experimental studies are required to substantiate our understanding of these complex embryological anomalies on the basis of currently available hypotheses.

This case doesn’t fit into this classification scheme and try to elucidate its embryological basis, with review of relevant literature. They also attempt to include this variety into the existing classification system of SCMs. 1).


A 52-year-old woman had hemicords within a single dural sac with a dorsal bony septum at the L5 level. A 9-year-old boy had hemicords within a single dural sac with a ventral bony septum and fibrous extension at the L3 level. Both patients underwent microsurgical treatments for removing the bony septum, detethering the spinal cord, and sectioning the filum terminale. The surgical procedure revealed an extradural partial bony septum and hemicords within an intact single dural sac in each patient. Both patients were discharged from the hospital without de novo nerve dysfunction. Published cases have validated that types I and II SCM can overlap.

Sun et al. recommend recent type 1.5 SCM as a normative terminology for this overlapping SCM and report two rare cases of this SCM.

They proposed an associated pathogenesis consisting of uneven distribution and regression to explain type 1.5 SCM. Furthermore, they postulate that the amount of condensing meninx primitiva might determine whether the left bony septum has fibrous extensions to the opposite dura in type 1.5 SCM 2).


1)

Meena RK, Doddamani RS, Gurjar HK, Jagdevan A, Chandra SP. “Type 1.5 split cord malformations: an uncommon entity”. World Neurosurg. 2019 Sep 23. pii: S1878-8750(19)32506-9. doi: 10.1016/j.wneu.2019.09.076. [Epub ahead of print] PubMed PMID: 31557552.
2)

Sun M, Tao B, Luo T, Gao G, Shang A. Type 1.5 Split Cord Malformation : A New Theory of Pathogenesis. J Korean Neurosurg Soc. 2021 Nov 22. doi: 10.3340/jkns.2020.0360. Epub ahead of print. PMID: 34802216.
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