Lipomyelomeningocele with terminal myelocystocele

Clinical History

3 days old term female presented with a sacral mass.

Imaging Findings

There is a dorsal dysraphic defect involving the L4-S2 levels. There is a complex mass effect containing fat and cerebrospinal fluid (CSF) spaces, outlining a spinal cord tethering into the posterior wall of the expanded lumbosacral spinal canal at the dorsal dysraphic defect. There is identifiable broad-based attachment of the neural placode in the posterior meningocele wall with near horizontal nerve roots extending anteriorly to the lower lumbar neural foramina. The fatty component of the mass is predominantly superficial to the CSF containing space, comprising the dorsal component of the mass.
There is associated dilated spinal cord central canal (hydromyelia) continuous with a dilated cystic space at the neural placode in keeping with a terminal myelocystocele.

Discussion

Spinal dysraphisms are congenital abnormalities of the spine and spinal cord associated to posterior element defects. (I) Spinal development is divided into gastrulation, primary neurulation and secondary neurulation.
During gastrulation (weeks 2-3), the embryonic disk progresses from a bilaminar to a trilaminar structure composed of ectoderm, mesoderm and endoderm, with a midline cells migration forming the notochord. During primary neurulation (weeks 3-4), the notochord and the overlying ectoderm form a neural plate, which neurulates (separates from the ectoderm), folding to form the neural tube, which closes bidirectionally in a zipper-like fashion defining a cranial neuropore that closes around day 25 and a caudal neuropore which closes around day 27 or 28. [1, 2]. During secondary neurulation (weeks 5-6), a solid caudal cell mass forms near the caudal neuropore, which subsequently cavitates to form a secondary neural tube, forming the tip of the conus medullaris and filum terminale. The conus medullaris contains the terminal ventricle, a remnant of the secondary neural tube. [1, 2, 3]
The neural placode is a segment of flattened neural tissue that fails to neurulate from the ectoderm, which may be covered by fat and/or skin from ectodermal origin. A terminal placode lies at the caudal end of the spinal cord, while a segmental placode is more proximal. [1]
Spinal dysraphisms (SDs) are classically divided in open (Open SDs) if neural tissue is exposed to the environment and closed (Closed SDs) if the neural tissue is covered by skin.
Open SDs include myelomeningocele (98.8% of the cases), myelocele, hemimyelomeningocele and hemimyelocele.
Closed SDs may present with subcutaneous mass, without subcutaneous mass and as complex dysraphic state. Closed SDs with subcutaneous mass include lipomas with dural defect, lipomyelocele, lipomyelomeningocele, terminal myelocystocele and meningocele. Closed SDs without subcutaneous mass include intradural lipoma, filum lipoma, tight filum terminale, persistent terminal ventricle and dermal sinus tract.
Complex dysraphic states are disorders of midline notochordal integration (such as dorsal enteric fistula, neurenteric cysts, and diastematomyelia) and disorders of notochordal formation, such as caudal agenesis and segmental spinal dysgenesis.
MRI is vital to diagnose these lesions and delineate their anatomy, helping in classification, treatment planning, parent counseling, and follow-up. [1, 4]
This is a rare case of a lipomyelomeningocele with a terminal myelocystocele. Lipomyelomeningocele: Lipo (lipoma/fat), Myelo (neural tissue), Meningo (meninges) Cele (herniation). Myelocistocele: herniation of large terminal ventricle into a posterior meningocele.

Differential Diagnosis List

Final Diagnosis

Lipomyelomeningocele with terminal myelocystocele.

URL:	https://eurorad.org/case/14730
DOI:	10.1594/EURORAD/CASE.14730
ISSN:	1563-4086