Retained medullary cord and terminal myelocystocele as a spectrum: case report
Youngbo Shim1, Hyun Joo Park2, Kyung Hyun Kim1
1Division of Pediatric Neurosurgery, Seoul National University Children's Hospital, 101 Daehak-ro, Jongno-gu, 03080, Seoul, Republic of Korea.
Abstract:
The caudal portion of the spinal cord, the medullary cord, is formed by secondary neurulation. One of the distinctive features of secondary neurulation compared to primary neurulation is that the medullary cord normally degenerates into a filum in humans. Various anomalies have been known to originate from degenerating process errors. One anomaly is terminal myelocystocele (TMCC), which is a closed spinal dysraphism with an elongated caudal spinal cord. The terminal part is filled with cerebrospinal fluid (CSF) and protrudes into the dorsal extradural space. Another anomaly is the retained medullary cord (RMC), which is a nonfunctioning cord-like structure extending to the cul-de-sac. In a 1-month-old boy, we identified an RMC with cystic dilatation of the caudal end extending to the epidural space at the very bottom of the cul-de-sac, resembling a degenerating terminal balloon, which is an essential feature of TMCC. Hence, this case may be considered an intermediate form between TMCC and RMC. This case provides clinical evidence that TMCC and RMC share the same pathoembryogenic origin, namely, failure of the regression phase of secondary neurulation.
Insights
Secondary neurulation errors can cause spinal cord anomalies. A case report suggests terminal myelocystocele (TMCC) and retained medullary cord (RMC) may share a common origin due to failed regression.
Area of Science:
- Neuroscience
- Developmental Biology
- Embryology
Background:
- Secondary neurulation forms the caudal spinal cord, which normally degenerates into the filum terminale.
- Errors in this degeneration process can lead to spinal dysraphism, including terminal myelocystocele (TMCC) and retained medullary cord (RMC).
Observation:
- A case of retained medullary cord (RMC) in a 1-month-old boy exhibited cystic dilatation at its caudal end, resembling the terminal balloon seen in terminal myelocystocele (TMCC).
- This finding occurred at the cul-de-sac's base, extending into the epidural space.
Findings:
- The observed case presented features intermediate between RMC and TMCC.
- This suggests a shared pathoembryogenic origin for both conditions, stemming from a failure in the regression phase of secondary neurulation.
Implications:
- This case provides clinical evidence supporting a unified pathoembryogenic theory for TMCC and RMC.
- Understanding this shared origin can inform diagnostic and therapeutic strategies for these congenital spinal anomalies.
