This fetus is scanned at 18 weeks, and the following images are obtained. The mass is on the left side and it displace the heart to the right. No other anomalies are detected and in particular the spine appears sonographically normal.

Although not initially appreciated, one can suspect in retrospect that the relative position of the head compared to the chest is too low. If one draws the putative outlines of the head and chest the anomaly is more visible.

The spine appeared normal... but as the X-ray below demonstrated it was not.

This is the large left-sided cystic mass.

So prenatally the findings were limited to a large left-sided cystic mass that displaced the heart to the right. The initial diagnoses were:

• a giant cystic adenomatoid tumor
• a lung cyst
• a gastrointestinal duplication 
• a pyloric atresia
• a neurenteric cyst

A puncture of the mass returns fluid with epithelial cells and bile, and the fluid reaccumulated rapidly after punction. Because of the high risk of pulmonary hypoplasia and the size of the lesion, the patient elected to terminate the pregnancy.

The autopsy of the fetus demonstrated the distended abdomen and chest.

The X-rays reveals segmentation anomalies between C2 to T9 with dysraphism at the T6-T7 levels. A myelogram demonstrates the absence of communication between the neural sac and the mass.

The cystic mass represents a mechanically distended duodenum (115*60*40mm) that enters the chest via a diaphragmatic hernia and is tethered (see second image) to the vertebral body of T6-7 ...

... by an adhesion to the ventral aspect of the spinal cord (on the lower aspect of the pathology specimen)

The autopsy confirms the pulmonary hypoplasia.

Discussion

The most tempting diagnosis prenatally was that of a neurenteric cyst, but the spine was considered "too normal" for a neurenteric cyst and the fluid from the puncture (bile !) did not fit the diagnosis. At autopsy a neurenteric cyst was excluded because of the lack of communication between the cerebro-spinal fluid space and the content of the cyst. The finding of a direct adhesion of the gastrointestinal tract to the spinal cord through a vertebral cleft is diagnostic of split notochord syndrome.