Meningocele is characterized by spina bifida and herniation of the meninges through a spinal defect, but that does not seem to be the case here. To be sure, let's look at Figure 4, Figure 5, and Figure 6, which are axial images of the fetal spine.
After studying the aforementioned images, there is no obvious herniation of the meninges through a dorsal or ventral defect in the spine. However, there is an obvious anomaly visible in the images of the axial section of thoracic vertebrae, which was also visible in the images of the coronal section of the thoracic vertebrae. The anomaly is some form of division of the spinal canal.
Could this be hydromyelia, which is characterized by dilation of the central canal of the spinal cord? Or is it diplomyelia, which is division of the cord into two complete halves? Diplomyelia is possible, since there is a division of the cord in the region of the affected thoracic spine.
True diplomyelia is characterized by near-total division of the spinal cord, which is not the case here. The division is localized to the affected lower thoracic spines. In addition, there is a vertical echogenic, possibly bony, septum within the affected thoracic vertebrae. This finding suggests the possibility of diastematomyelia. This condition is seen as a partial or complete bony septum or fibrous septum that divides the spinal canal (localized to affected spine), with partial division of the spinal cord in the affected parts only.
To review, the findings in this fetus include the following:
- Midline bony spur or septum in the lower thoracic spine.
- Normal central canal of the spinal cord.
- No significant dilatation of cerebral ventricles.
- Division of the spinal cord localized to the affected thoracic spines.
- Normal spinal cord above and below the affected vertebrae.
The most common anomaly associated with these findings becomes our final diagnosis, which is diastematomyelia.
Diastematomyelia is a very rare anomaly characterized by clefting of the spinal cord due to a partial or complete bony or fibrous septum within the spinal canal. This results in localized division of the spinal cord, which roots into two parts on either side of the septum. This division may affect one or more vertebrae and usually involves the lower thoracic or upper lumbar spines. However, any part of the spine may be involved. It is said to be caused by separate closure of two hemicords during early gestational stage. Among the associated anomalies are club feet, kyphosis, and scoliosis.
The prognosis in this fetus is quite good given the absence of any associated anomalies and the affected region being localized to just two thoracic vertebrae. Surgical removal of the spinal bony septum will usually result in excellent recovery, although some cases may show limited neurological deficits.
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Suma V, Marini A, Panagopoulos P, et al. Diastematomyelia. Available at: http://sonoworld.com/fetus/page.aspx?id=108. Accessed April 6, 2015.