Retained medullary cordの2症例

• Published in: 脊髄外科 Vol. 34; no. 1; pp. 79 - 83
• Main Authors: 吉藤, 和久, 大森, 義範, 木村, 幸子, 高橋, 秀史, 小柳, 泉, 三國, 信啓
• Format: Journal Article
• Language: Japanese
• Published: 日本脊髄外科学会 2020
• Subjects: retained medullary cord; secondary neurulation; spina bifida
• ISSN: 0914-6024; 1880-9359
• DOI: 10.2531/spinalsurg.34.79

A retained medullary cord (RMC) is an infrequently reported closed spinal dysraphism caused by regression failure of the medullary cord during secondary neurulation. RMC is characterized by the lack of conus medullaris and filum terminale formation on magnetic resonance imaging (MRI) and under a microscope. The remaining robust elongated medullary cord often causes tethered cord syndrome. We herein report two cases of RMC―one of the stand-alone type and the other associated with terminal myelomeningocystocele―and discuss a definition of RMC based on embryology that is yet to be completely accepted. We also consider surgical procedures.  Case 1 : A 4-year-old girl who presented with a lumbosacral subcutaneous mass at birth had continued enuresis until 4 years of age. MRI revealed a gradually shrinking spinal cord reaching the dural cul-de-sac without forming the conus medullaris and filum terminale. She underwent untethering surgery using the electromyographic procedure, and the function of the true conus medullaris and the true spinal nerves could be defined. The medullary cord and coccygeal nerves identified as non-functioning structures were resected. Her postoperative course was uneventful and the enuresis disappeared within 7 months after surgery.  Case 2 : A 3-month-old girl showed a lumbosacral subcutaneous mass with a small dimple at birth. MRI indicated a robust elongated spinal cord without formation of the conus medullaris and filum terminale. Sacral meningocele and enlargement of the caudal central canal, namely the terminal myelomeningocystocele, were observed. She underwent repair of the terminal myelomeningocystocele and untethering, using the same electromyographic procedure as that used in case 1.  It may be appropriate to define stand-alone RMC (as in case 1) as “narrow-sense RMC” and RMC associated with other anomalies (as in case 2) as “broad-sense RMC.” Otherwise, the definition of RMC should consist entirely of stand-alone RMC. Electrophysiological procedures are indispensable for defining the point of untethering.