Twin-twin transfusion syndrome - fetal MRI

Case contributed by Dr Alexandra Stanislavsky

Presentation

Stage 3 twin-twin transfusion syndrome.

Patient Data

Age: Maternal age 25 years
Gender: Female
MRI

MRI prior to laser photocoagulation; GA 19w6d

Two fetuses present.

Lower twin: smaller and stuck against the uterine wall with its head positioned nearest the cervix. This is the donor twin. There is borderline asymmetric lateral ventriculomegaly with the left lateral ventricular trigone measuring 10 mm and the right 8 mm.

Upper twin: surrounded by a large amount of amniotic fluid and was highly mobile as a result, during the examination. 3 mm focus of susceptibility related signal loss and subtle localised brain parenchymal volume loss in the left frontoparietal region. The findings are most consistent with a small, established haemorrhagic cortical infarct. Generalised symmetric widening of the CSF spaces is consistent with the recipient status of this twin and is a well recognised and often transient finding in such fetuses. Otherwise normal apperance of the brain and normal cerebral biometry.

The deepest pocket of amniotic fluid surrounding this twin is approximately 10 cm.

Placenta: The placenta is anterior and somewhat thin for this gestation measuring 16 mm in maximum AP diameter. 

 

MRI

Post laser photocoagulation

Fetal MRI obtained 5 days post laser photocoagulation.

Discordant amniotic fluid is no longer seen and the smaller of the 2 twins is now mobile and situated in the right side of the amniotic cavity. 

Twin 1 (previous upper twin - now left cephalic)
Established haemorrhagic infarction again noted in the left frontal lobe. This is now more obviously associated with localised disruption of the zonal anatomy, but otherwise has not changed since the previous examination. No new haemorrhage or infarction is identified.

Twin 2 (previous lower twin now right breech)
Persistent borderline lateral ventriculomegaly which is stable, with each lateral ventricular trigone measuring 10 mm. 

For ease of anatomic assessment, views of both fetal heads have been cropped and rotated into standard orientation. Please refer to sequence labels to distinguish the cephalic vs breech twins.

Annotated image

Annotation of normal cerebral development at 20 weeks

At 20 weeks gestation, the interhemispheric and Sylvian fissures are always present. Note the shallow, rounded appearance of the Sylvian fissure at this stage. Over the next few weeks, it will become deeper, more squared and then angular as the temporal lobe folds over to cover the operculum. Other fissures have not yet appeared. 

Also at this stage, we begin to see the normal 5 layered laminar appearance, which will persist until approximately 30 weeks gestation. From inner to outer, the layers are: 1.Ventricular zone (arrowhead); 2. periventricular fibre-rich zone (dotted arrow); 3. intermediate zone (curved arrow); 4. sub-plate (long thin arrow); 5. cortex (short thick arrow). 

Note on the right side, localised disruption of the normal laminar pattern near the site of previous antenatal haemorrhage in this fetus (marked #).

The ganglionic eminences are low signal, highly cellular areas present within the subventricular zone, and still prominent at this stage; they will become less so as cells migrate from the ganglionic eminences to the neocortex, grey matter nuclei, thallami and hippocampi. 

Case Discussion

This case demonstrates features of twin-twin transfusion syndrome with fetal MRI, prior to and after successful laser photocoagulation.

Both fetal brains are mildly abnormal. The donor twin has borderline ventriculomegaly, and the recipient twin has a small, established left frontal haemorrhagic infarct. Fetal cerebral appearances including sulcation and lamination are otherwise normal and age appropriate. Annotated images address the features of normal fetal brain development at 20 weeks which are seen in this case.

Case courtesy of Prof Stacy Goergen.

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Case information

rID: 51114
Case created: 4th Feb 2017
Last edited: 6th Apr 2017
System: Obstetrics
Inclusion in quiz mode: Included

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