Department of Neurosurgery, Fukuoka Children's Hospital, Fukuoka, Japan.
Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Pediatr Neurosurg. 2022;57(3):184-190. doi: 10.1159/000523976. Epub 2022 Mar 8.
The retained medullary cord (RMC) is a newly defined entity of closed spinal dysraphism that is thought to originate from regression failure of the medullary cord during the last phase of secondary neurulation. The terminal myelocystocele (TMC) is an unusual type of closed spinal dysraphism, characterized by localized cystic dilatation of the terminal part of the central canal that then herniates through a posterior spinal bifida. The co-occurrence of RMC and TMC is extremely rare.
We treated a baby girl with a huge sacrococcygeal meningocele-like sac with two components. Untethering surgery and repair surgery for the sac revealed that RMC, associated with intramedullary arachnoid cyst (IMAC), was terminated at the bottom of the rostral cyst, forming the septum of the two cystic components, and the caudal cyst was TMC derived from the central canal-like ependymal lining lumen (CC-LELL) of the RMC at the septum. IMAC within the RMC communicated with TMC, and both contained xanthochromic fluid with the same properties.
We speculated that the mass effect of the coexistent IMAC impeded the flow of cerebrospinal fluid in the CC-LELL within the RMC and eventually formed a huge TMC. In surgical strategies for such complex pathologies, it is important to identify the electrophysiological border between the functional cord and nonfunctional RMC and the severe RMC to untether the cord, as with a typical or simple RMC.
残留的髓芯（RMC）是一种新定义的闭合性脊髓脊膜膨出实体，据认为它起源于继发性神经发生的最后阶段髓芯的回归失败。终末脊髓脊膜膨出（TMC）是一种不常见的闭合性脊髓脊膜膨出，其特征是中央管末端的局部囊性扩张，然后通过后脊柱裂疝出。RMC 和 TMC 的同时发生极为罕见。
我们治疗了一名女婴，她的骶尾部有一个巨大的脑膜膨出样囊，由两个部分组成。对囊进行松解和修复手术发现，RMC 伴有髓内蛛网膜囊肿（IMAC），在颅侧囊肿的底部终止，形成两个囊性成分的隔膜，而尾侧囊肿是源自 RMC 的中央管样室管膜衬里管腔（CC-LELL）的 TMC。RMC 内的 IMAC 与 TMC 相通，两者均含有黄变液，性质相同。
我们推测共存的 IMAC 的质量效应阻碍了 RMC 内 CC-LELL 中的脑脊液流动，最终形成了一个巨大的 TMC。在这种复杂病变的手术策略中，重要的是要识别功能性脊髓和非功能性 RMC 以及严重 RMC 之间的电生理边界，以便像典型或简单的 RMC 一样松解脊髓。
