Division of Pediatric Neurosurgery, Seoul National University Children's Hospital, Seoul, Republic of Korea.
Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Republic of Korea.
Childs Nerv Syst. 2021 Jun;37(6):2051-2056. doi: 10.1007/s00381-020-04943-6. Epub 2020 Oct 28.
Retained medullary cord (RMC) is thought to be a product of arrested secondary neurulation during the regression phase. A cord-like structure with a caudal non-functional part ends at the cul-de-sac. If the arrest occurs at the cavitation phase of secondary neurulation, the medullary cord has a cystic portion making "RMC of cystic type."
We report a case of a 4-month-old girl who had a low-lying conus with an extradural-looking dorsal cyst. Preoperative diagnosis was RMC with a lumbosacral extradural cyst such as an arachnoid cyst. At surgery, we found that the extradural cyst was an extension of dural sac with the caudal portion of the cystic RMC inside. The RMC was untethered and the dural sac was reconstructed. The histopathologic examination revealed findings compatible with cystic RMC attached to the cul-de-sac.
We regard this case as an intermediate form between the typical RMC in which is regarded as regression arrest occurred after the terminal balloon collapsed and the medullary cord detached from the skin to the normal cul-de-sac, and the terminal myelocystocele which is considered the result of arrest at the phase of the persisted terminal balloon attached to the skin.
残留的髓索（RMC）被认为是在回归阶段次级神经套发生停止时的产物。一种具有尾部无功能部分的索状结构终止于终末隐窝。如果在次级神经套的囊泡形成阶段发生阻滞，髓索就会有一个囊状部分，形成“囊性 RMC”。
我们报告了一例 4 个月大的女孩，其圆锥位置较低，有一个硬膜外样的背部囊肿。术前诊断为 RMC 伴腰骶部硬膜外囊肿，如蛛网膜囊肿。在手术中，我们发现硬膜外囊肿是硬脑膜囊的延伸，囊性 RMC 的尾部位于囊肿内。RMC 没有被束缚，硬脑膜囊被重建。组织病理学检查显示与终末隐窝附着的囊性 RMC 相符的发现。
我们认为这种情况是典型 RMC 的中间形式，典型 RMC 被认为是在终末气球塌陷后，脊髓索从皮肤退缩到正常终末隐窝的回归停止，而终末脊髓脊膜膨出则被认为是终末气球附着在皮肤时持续存在的阶段发生阻滞的结果。
