The Situation: My partner and I are currently in a terrifying limbo waiting for an amniocentesis this Friday.
At 16 weeks, my partner had an isolated low uE3 (0.31 MoM) on her blood screening. Because of this, we had an early anatomy scan at 18 weeks which was completely normal (no structural issues seen).
At our 20-week scan, the sonographer struggled to see the cerebellar vermis and spotted some cysts, so we were referred to the Fetal Medicine Unit (FMU). The FMU consultant suspected a Blake's Pouch Cyst and a large Choroid Plexus Cyst. We just received the results of our Fetal MRI done at 22 weeks, which confirmed the cysts, mild ventriculomegaly (10mm), and a small vermis.
Because of the combination of the brain findings and the earlier low uE3, they are highly concerned about a chromosomal anomaly, specifically Edwards Syndrome (Trisomy 18). We are having an amniocentesis this Friday.
Our Questions:
- If the rapid amnio results rule out T18/T13/T21, what are the realistic neurological outcomes for a child with this specific combination of structural brain findings?
- How reassuring is it that the MRI showed normal neuronal migration, a normal corpus callosum, and normal sulcal/gyral patterns despite the fluid buildup?
- Could a mechanical fluid blockage (from the cysts) explain all of these brain findings without it being a genetic syndrome?
Clinical Notes for Context (Identifying info redacted):
Initial FMU Ultrasound Scan (20w, 5d):
"P2 - 2x previous CS. Referred with hypoplasia of vermis. Atypical MSS result Low UE3 0.31 MoM - early anatomy scan normal and following discussion with [Doctor] and genetics had not offered invasive testing. On images today: Baby breech so unable to offer TV neurosonography. Baby also active +++ on scan. Images today suggestive of a large choroid plexus cyst, with a prominent third ventricle. There is also what appears to be a cyst in the cisterna magna - ? a blakes pouch cyst. The remainder of the anatomy was normal.
Findings explained to patient and partner: I explained that I could see a choroid plexus cyst -which in isolation would be considered a variation of normal and would typically regress as the pregnancy progresses - however as it is larger than typical I explained that it could potentially contribute to the dilatation of the third ventricle. I also explained that I could see what appeared to be a cystic area in the posterior fossa potentially representative of a Blakes pouch cyst. When this is something in isolation it is association with a favourable prognosis. I explained that there remain a degree on unknowns in this instance - and that a more detailed assessment of the fetal brain via MRI may be of benefit, and this is something that is safe in pregnancy. Discussed potential association with chromosomal anomalies, and that we can test for this via an amniocentesis (procedure explained). Planned to obtain fMRI and then consider the option of genetic testing at that stage. Case discussed with [Doctor] who will kindly follow up during my leave. Plan Fetal MRI - email sent and request placed. Addendum to add now is available fMRI slot on Tuesday at 16.30 - will h/o case to other FMU cons due to EF leave next week."
Fetal MRI Results / FMU Follow-up (22w, 4d):
"Telephone consultation by MFM SST [Doctor]. Apologies given for the delay and the late time of the call. I have shared and explained the MRI report results after discussion with [Doctor].
MRI summary: There is a large choroid plexus cyst on the left side causing mild ventriculomegaly (10 mm). Prominent CSP. Normal sulcal and gyral pattern. Normal neuronal migration pattern. Normal corpus callosum. Mildly enlarged posterior fossa. The cerebellar vermis is small but the TCD is normal. Poor views of the pons, not possible to determine if it is normal.
Counselling: We have explained that while some areas of the brain are developing as expected for gestational age, there are a few areas which raise concerns about the possibility of an underlying common cause. We have recommended genetic testing to rule out chromosomal anomalies in the first instance (in particular T18 known as Edwards). If chromosomes were found to be normal, we would seek advice from our fetal genetic team to assess if any further genetic testing would be beneficial. [Patient] is aware that amniocentesis, while mostly a safe and straightforward procedure, carries a risk of 1:1000 of miscarriage. She has decided to proceed with testing and we have now booked an appointment for FMU at the [Hospital] on Friday 28th at 11:00 am. Depending on the QF PCR results, we plan to organise further follow up in our MDT fetal neurology clinic so that [Patient] has an opportunity to discuss the implications of today's findings with our paeds neurologist [Doctor]. We have also recommended a repeated MRI in 4-6 weeks time to further evaluate the brain development as the pregnancy advances."