Antenatal and postnatal imaging of a double diastematomyelia without other malformation

Clinical History

Female newborn at term presented for postnatal imaging of a thoracic diastematomyelia with bony septum revealed by routine fetal ultrasound at 28 weeks gestation. Neurological examination was unremarkable and the baby had no cutaneous dysraphism markers.

Imaging Findings

Prenatal ultrasound at 28 weeks gestation demonstrated a hyperechogenic focus with acoustic shadowing in the thoracic spinal cord within two hemicords and intact overlying soft tissues. At birth, ultrasound showed two hemicords from T10 to L2 with a bone septum in between. A second enlargement of the spinal cord with partial double spinal cord was visible at the level of the conus medullaris, which ended at L3. There was no cord tethering or intradural mass and real-time scanning showed adequate motion of nerve roots. Additional findings included a 3 mm large syrinx extending from T5 to T7. Postnatal MRI obtained at 2 weeks confirmed the presence of a bony spur at level T12, dividing the spinal canal in two compartments each containing a hemicord from level T10 and joining at level L2. MRI did not identify the more caudal incomplete double hemicords.

Discussion

Diastematomyelia results from a persistent endomesenchymal tract connecting the endoderm and ectoderm, with consequent splitting of the notochord and the overlying folding neural plate and formation of two separate neural tubes and hemicords. [1] In type I diastematomyelia, both hemicords are enclosed in distinct dural sacs separated by extradural cartilage and bony spur in between. In type 2 diastematomyelia, there is no dural compartmentalization of the spinal cord and the two hemicords lie in the same dural sac with a partial or total fibrous midline septum.

Thorough examination for associated dysraphism abnormalities and concurrent cord tethering is necessary since early surgery can decrease secondary neurologic deterioration, including worsening scoliosis, lower limb deformities and sphincter dysfunction. [2] Surgical management consists of untethering the hemicords by resecting the bony spur and the fibrous septum, dural plasty and conus medullaris release, in order to enable longitudinal growth of the spinal cord in the growing spine. [2]

Classic antenatal ultrasound findings of type I diastematomyelia include widening of the spinal canal in the coronal view and echogenic focus traversing the spinal column in the axial view. [3] Fetal MRI does not provide more information to the diagnosis unless mother abdominal habitus, oligohydramnios and posteriorly facing fetal spine limit screening. [4, 5]
Postnatal ultrasound confirmed the finding of type I thoracic diastematomyelia and further revealed a lower type II diastematomyelia and a more rostral syrinx, thereby being part of the rare cases of composite-type diastematomyelia previously described [1, 6-8] and illustrating the common reported association of diastematomyelia and syringomyelia. [9, 10]
Noteworthy, only early postnatal ultrasound readily depicted the lower type II diastematomyelia, supporting the use of high resolution ultrasound for scanning of the newborn spinal cord during the window of non-ossified cartilaginous posterior processes. [11] In our patient, postnatal MRI was less accurate than ultrasound. It was unable to identify the additional lower site of cord tethering resulting from a less rigid but potentially harmful fibrous band that could have threatened the surgery outcome of the upper lesion. Furthermore, it did not add any contribution to the diagnosis made by ultrasound workup.
Our case illustrates a diastematomyelia diagnostic on antenatal ultrasound and the importance of postnatal ultrasound to achieve as much as possible just after birth. Postnatal MRI should be reserved for pre-operative assessment of the dysraphism.

Differential Diagnosis List

Final Diagnosis

Type I and type II diastematomyelia with associated syringomyelia.

URL:	https://www.eurorad.org/case/13043
DOI:	10.1594/EURORAD/CASE.13043
ISSN:	1563-4086