Borderlands in Obstetrical Ultrasound

Large Cisterna Magna and Dandy-Walker Spectrum

Our last topic will be the large cistern a magna or the Dandy Walker spectrum.

The cistern a magna is generally considered to be normal between two and 10 millimeters, although I consider up to 12 millimeters to be okay. If it's more than this, it's considered too large. If it's an isolated finding and the ventricles are normal and no other CNS lesions, most likely a very good outcome.

But the key to checking out the large cisternum magnet is make sure there's a verus present. We'll go over this in just a few seconds.

And remember, the Danny Walker spectrum is a continuum from the large cisterna mag, which is more benign to the Dandy Walker variant, to the more severe Danny Walker Malformation syndrome, where you have a dilated fourth ventricle absent inferior verus, and a large cistern of magna, oftentimes with hydrocephalus and other abnormalities.

Examples of Large Cisterna Magna

Here's an example of a large cistern of Magna 13 millimeters. You see the verus is present. There's no continuation of the cisterna mag with the fourth ventricle, and the ventricles are totally normal six millimeters normal outcome.

Another patient did have verian hypoplasia. You did see a communication through the inferior verus from the cisterna mag to the fourth ventricle here. You see it persisting in here, and this patient actually did have a little bit of developmental delay.

Remember to regard the verus here's the superior verus the inferior verus, and this midline shot. Here's the fourth ventricle cistern Magna, and the verus is the entity that lives in the middle, the cerebellum, and this is the inferior verus. There's also superior verus and lots of sub nuclei as well. But the inferior verus is key to analyzing the large cistern a magna here's a large cistern a Magna 14 millimeters. 14 millimeters, but again, there's no communication with the cisterna magna and the fourth ventricle normal outcome.

First Trimester Cases and Variants

This is a case from the literature recently, the Journal of Ultrasound and Medicine this month had a case or two cases discovered in the first trimester around 11 and a half weeks of this dilated cystic structure in the back of the brain that turned out to be a Danny Walker variant. One of the cases was terminated and the other one had an MRI that did show some abnormalities in the brain, so it can be seen in the first trimester.

This is like a second case from the G case series that shows the inferior inferior verian hypoplasia. Here's the fourth ventricle with communication in the cistern of Magna and the pons here.

Another case of Danny Walker. This had verian hyperplasia. You see communication from the Cyn Mag to the fourth ventricle. Here again, communication cistern magnet to the fourth ventricle absent of verus inferior verus a patient who had a Frank Danny Walker malformation with the dilated cyst Magna. And you can see the complete obliteration inferior verus with communication with the fourth ventricle here and marked dilatation of the ventricles. Lateral Vent measure 22 millimeters here. And here's another clip showing the huge cisterna magna communicating with the fourth ventricle. Danny Walker malformation.

Another example of just a mega cisterna Magna that looked quite striking initially, but see, the verus is intact. There's no communication with the fourth ventricle, and this baby's done quite well.

In the case of Danny Walker malformation, you see ventricular mely, and you can see the fourth ventricle communicating with thes cisterna mag, which in this case is not all that big.

Another example of cisterna of Danny Walker variant. This is an inferior mian aplasia, but there's no ventricular dilatation here. Just communication with the cisterna magna and the fourth ventricle.

MRI Examples and Coronal View Considerations

It's just a couple of MRIs to reinforce the idea that there is a mega cisterna mag, which has a good prognosis here, and the arachnoid cyst, which probably does not have a good prognosis until you take care of the arachnoid cyst, but it can be quite mass like and compress the pons and the midbrain and brainstem.

Always be aware of the coronal view. If you're scanning more clonally, you can get the fourth ventricle extending through the framing of Luka through the cistern mag. Make it look like there is some inferior verian aplasia or hypoplasia. But this is just a reflection of the altered coronal view rather than being a truly axial view.

Differential Diagnoses

A couple other things in the differential for large ci sternal magna verian hypoplasia is Blake's pouch cyst, which can be a very wide spectrum from asymptomatic to full blown hydrocephalus. So kind of a variable presentation.

And Bert syndrome, which is a mostly autosomal recessive spontaneous mutation that has primarily verian absence or hypoplasia, and quite significant neurologic abnormalities, including hypotonia, developmental delay, ataxia, abnormal eye movements. And this condition should be suspected when it's abnormal. The shaped fourth ventricle connecting to a normal sized cisterna Magna.

Here's a Blake's pouch cyst with a communication between the fourth ventricle and the cisterna magna outcomes of posterior FOSS anomalies.

Studies on Outcomes

Study from the University of Cincinnati recently looked at 59 patients, nine Danny Walker malformation cases, sort of the full blown spectrum. Three six with the verian hypo GSIs or hypoplasia, sort of the Danny Walker variant, and then 14 with mega cistern and magna only. Those with isolated mega cisterna mag turned out to be normal. The verian hypoplasia were mostly normal, and the presence of intracranial abnormalities or abnormal brain stems were associated with poor outcomes.

A study from Italy last year of 105 patients with posterior fossa fluid collections found that they're fairly mixed etiology Blake's pouch cyst in 32 mega cisterna magna in 26, 27, Danny Walker malformation in 26, Verian Hypoplasia and 17 cerebellar hypoplasia and two, and arachnoid cyst in one. The ultrasound diagnosis was accurate in 88% of cases. An MRI was only more accurate. In one out of 51 cases, pleio was present in 26%, and Blake's pouch cyst, mega cyst, and Magna had spontaneous resolution, one third of cases. So sometimes they'll go away during the pregnancy, but the bottom line take home messages are over. 90% of isolated findings had normal developmental outcome at one to five years, and isolated Danny Walker malformation, Verian Hypoplasia had normal developmental outcome in 50% of cases.

Summary of Borderlands of OB Ultrasound Topics

So summary of the borderlands of ob ultrasound in these topics I've discussed are echogenic bowel. Always remember to turn off harmonics, evaluate the bowel in that situation. If it is echogenic with conventional imaging, there is a relative risk of seven for aneuploidy, especially if the patient is high risk, either elderly or older than 35, or has abnormal serum screening markers.

In the case of the echogenic intracardiac focus, it's so common we tend to ignore it if it's the isolated finding. Much more commonly seen in thin patients with a cardiac apex anteriorly, the NAL folder. Translucency thickening is a high positive predictive value for Trisomy 21, but other abnormalities, especially lymphatic disorders or cardiac abnormalities in mild ventricular magaly, I think we may wanna consider raising the threshold for ventricular magaly to 12 millimeters, especially in males.

If the ventricles are 12 to 15 millimeters mildly dilated, follow those patients up with one or two ultrasounds during the pregnancy. Do a very detailed fetal survey, and probably get a fetal MRI in cases of events, ventricles being more than 12 millimeters.

Large cisterna magnar, D walker, spectrum D remember the large cisterna mag, the normal cisterna mag is between two and 12 millimeters. There's no high dose cephas. It's generally a good prognosis, and that's all. Thank you.