Thalamomegaly - fetal

Case contributed by Dennis Odhiambo Agolah
Diagnosis almost certain


Primigravida at thirty-eight weeks gestation with fetal anomalies (abdominal) on a previous scan. To confirm the anomalies.

Patient Data

Age: 25 years
Gender: Female

Symmetrical fetal bi-thalamic homogeneous enlargement with resultant 5.60 cm trans-thalamic diameter (measured from the outer posterior thalami walls vertically). No other fetal intra-cranial pathology.

Associated diffuse unilaterally enlarged fetal left kidney measuring 202 cc in volume, that demonstrates multifocal anechoic cystic lesions interspersed within it's entire parenchyma (salt and pepper sign) with ipsilateral loss of cortical- medullary differentiation is noted. The fetal right kidney showed moderate hydronephrosis (labeled "h"). There was severe oligohydramnios attending.

Case Discussion

Multiple fetal anatomical anomalies in this presentation including features of unilateral left-sided recessive polycystic kidney disease (RPKD) and diffuse ipsilateral nephromegaly; contralateral right-sided fetal grade II-III hydronephrosis and; conspicuously symmetrical bi-thalamic bodies enlargement (thalamomegaly).

At term, the fetal trans-thalamic diameter may range between 3-4 cm however, in this case, the trans-thalamic diameter was 5.60 cm. Other studies have shown that 2-dimensional axial (length+width of either thalamus in millimeters) gives the same gestational age as the maternal LNMP, BPD, HC, AC and the FL 1. Using this approach, the fetal left thalamus body gives 34.0 + 28.90 mm = 62.9 weeks while the right thalamus gives 35.6 + 23.6 mm = 59.2 weeks gestation. The two, as can be seen, are above the expected 42 weeks of gestation.

There was severe liquor reduction noted as well and a general reduction in fetal gross motor/somatic movements. Whereas the biophysical profile score was 4/8, the Doppler tracings were normal and the composite gestational age by ultrasound of 37 weeks (against the maternal LNMP dating of 38 weeks) ruled out the presence of intra-uterine growth restriction.

No radiological imaging could be done postnatally as the baby succumbed three hours post-delivery with the neonatal demise clinically attributed to the congenital anomalies.

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