Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India.
Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India.
World Neurosurg. 2020 Jan;133:142-149. doi: 10.1016/j.wneu.2019.09.076. Epub 2019 Sep 23.
Split cord malformations (SCMs) are among the rare congenital spinal anomalies. In 1992, Pang et al. proposed the unified theory of embryogenesis and explained the formation of SCM type 1 and 2. This theory has been widely accepted in the neurosurgical literature, backed by several studies. However, there have been reports in the literature that defy both the classification as well as the formation of SCMs, based on the unified theory of embryogenesis. We report a case of SCM that does not fit into this classification scheme and try to elucidate its embryologic basis, with review of the relevant literature. We also attempt to include this variety into the existing classification system of SCMs.
An 11-year-old boy presented with low backache after trivial trauma. He was neurologically intact. Imaging showed low-lying tethered cord and a midline ventral bony spur (D12, L1) with a single dural sac encasing both the hemicords. Surgical exploration showed a ventral bony spur with 2 hemicords, enclosed in a single dural tube. Excision of the bony spur and detethering of the filum terminal were performed. The postoperative course was uneventful and the patient was discharged satisfactorily.
SCMs possibly represent a continuum of changes beginning at the gestational age of days 20-30. Terminology such as mixed or intermediate type is used to denote SCMs that show features of both type 1 and type II. We prefer using type 1.5 SCMs for all such cases, thereby avoiding confusion and maintaining uniformity in the nomenclature. However, further experimental studies are required to substantiate our understanding of these complex embryologic anomalies on the basis of current hypotheses.
脊髓分裂畸形（SCM）是罕见的先天性脊柱畸形之一。1992 年，Pang 等人提出了胚胎发生的统一理论，并解释了 1 型和 2 型 SCM 的形成。该理论得到了几项研究的支持，在神经外科学文献中得到了广泛认可。然而，文献中也有报道称，根据胚胎发生的统一理论，SCM 的分类和形成都存在争议。我们报告了一例不符合该分类方案的 SCM 病例，并尝试阐明其胚胎学基础，同时回顾相关文献。我们还试图将这种变异纳入现有的 SCM 分类系统。
一名 11 岁男孩在轻微创伤后出现腰痛，神经功能完整。影像学显示低位拴系脊髓和中线腹侧骨嵴（D12、L1），单一硬脊膜囊包裹两个半脊索。手术探查显示有一个腹侧骨嵴，有 2 个半脊索，被单个硬脊膜管包裹。行骨嵴切除术和终丝松解术。术后过程顺利，患者满意出院。
SCM 可能代表从妊娠第 20-30 天开始的一系列变化。使用混合或中间型等术语来表示具有 1 型和 2 型特征的 SCM。我们更喜欢使用 1.5 型 SCM 来表示所有这些病例，从而避免混淆并保持命名的一致性。然而，需要进一步的实验研究来证实我们基于当前假说对这些复杂胚胎学异常的理解。
