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What's your Diagnosis of this Fetus?: Page 2 of 3

What's your Diagnosis of this Fetus?: Page 2 of 3

B-mode Ultrasound Image Discussion

The fetal head shows a midline, rounded cystic area seen posterior to the thalamus and midbrain. What are the causes of a cystic lesion which is so deeply seated and indeed apparently menacing for the fetus? Upon further observation there is a linear extension of the cystic lesion posteriorly. Could an arachnoid cyst cause such an ultrasound appearance?

Ultrasound imaging of the fetal heart also showed mild cardiomegaly. Can the above findings and the fetal cardiomegaly be related? What are the conditions where there is a cystic lesion in the fetal brain that may also be associated with fetal cardiomegaly?

Observse the lesion in the Power Doppler (image 3).

Image 3: Power Doppler image of the fetal brain
Power doppler image  fetal brain

The Power Doppler image shows a striking appearance and is classical of a specific condition.

Image Discussion

There is a highly vascular lesion posterior to the thalamus and midbrain. This is in the location of the cystic area previously described, further it seems to drain posteriorly into a linear vessel. What are the diagnostic possibilities in this case?

Can these findings be produced by arachnoid cysts?

Arachnoid cysts are cystic lesions which are not vascular and they contain cerebrospinal fluid (CSF), therefore this cannot be an arachniod cyst.

Could this be a choroid plexus cyst?

Choroid cysts are found within the choroid plexus in the lateral ventricles. Our lesion is not in the correct location for a choroid cyst.

Are the findings consistent with a  porencephalic cyst?

Porencephalic cysts are the end result of intracranial hemorrhage and are not vascular on Doppler imaging. The answer again would be no, it is not a porencephalic cyst.

Is there a possibility of choroid papilloma?

Choroid papilloma tumors are relatively vascular but are almost always echogenic and not cystic.

The only remaining possibility is that this lesion is an enlarged vessel. The dilated vessel and draining vessel posterior to this have a striking appearance, almost like a “keyhole”. What vessel is found in this location and what is your diagnosis?

Add your opinions and continue to the final diagnosis.


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