2021 Volume 46 Issue 3 Pages 255-261
Background: A retained medullary cord (RMC) is a rare, closed spinal dysraphism caused by regression failure of the medullary cord during secondary neurulation. An RMC is a robust elongated cord-like structure extending continuously from the conus medullaris to the dural cul-de-sac. An RMC often causes tethered cord syndrome, evident by the absence of conus medullaris and filum terminal formation on magnetic resonance imaging (MRI) and intraoperative observation. The histopathology of the resected RMC is characterized by an ependyma-lined stratified cavity with a neuroglial core. A three-dimensional (3D) exoscope has recently become available for use in neurosurgical operations. It is compact; therefore, it provides a larger working space than that attained with the operating microscope. Herein, we report a case of an RMC with terminal meningocele that was surgically treated using a 3D exoscope.
Case presentation: A 2-month-old girl presented with a sacrococcygeal dimple at birth. She had no neurological deficits. MRI at 6 days old revealed a robust elongated spinal cord without formation of the conus medullaris and a cystic lesion on the ventrocaudal side of the dural sac. The lesion did not appear hyperintense on diffusion-weighted images. T2-weighted MRI obtained at 2 months revealed another cyst protruding into the subcutaneous tissue. We performed untethering and repair of the meningocele using a 3D exoscope. After opening the dura, a cord-like structure and a cyst at the ventrocaudal side of the dural sac were detected. The non-functioning cord-like structures were identified and resected to achieve untethering of the cord. The histopathology of the resected lesion showed a pseudostratified ependyma-lined cavity. Considering the above findings, we diagnosed the patient with an RMC. As there was no communication between the intra-arachnoid space and sacrococcygeal dimple, dermal sinus was excluded. Total resection of the RMC should be performed if the RMC is associated with a dermoid or epidermoid cyst. It is essential to keep RMC in mind and formulate a preoperative treatment strategy in cases of tethered cord with terminal meningocele.
