Cerebellar and frontal lobe hypoplasia in fetuses with trisomy 21: usefulness as combined US markers

Radiology. 2000 Feb;214(2):533-8. doi: 10.1148/radiology.214.2.r00fe40533.


Purpose: To confirm that cerebellar hypoplasia is ultrasonographically recognizable in second-trimester fetuses with Down syndrome and determine whether the combination of frontal lobe shortening and cerebellar hypoplasia is superior to either measurement alone as a marker of this abnormality.

Materials and methods: The frontothalamic distance (FTD) and transcerebellar diameter (TCD) were measured in 52 middle-trimester fetuses with euploid karyotypes and in 52 fetuses with Down syndrome. Receiver operating characteristic (ROC) curves were constructed with various thresholds for observed-to-expected ratios (O/Es) of the FTD, TCD, and average of these two parameters.

Results: The area under the average ROC curve, 0.80, was greater than that for either the FTD alone (0.75) or the TCD alone (0.76). At a 6% false-positive rate, the sensitivity for the detection of Down syndrome obtained with the average parameter was 34% better than that obtained with only the FTD and 12% better than that obtained with only the TCD. With an O/E threshold of 0.92 for the average parameter, an odds ratio of 16.3 and positive predictive value of 12.7% in the high-risk population were achieved.

Conclusion: Although both measurements are individually statistically significant, the combination of TCD and FTD measurements may be superior to the use of either parameter alone as a marker of trisomy 21.

MeSH terms

  • Adolescent
  • Adult
  • Area Under Curve
  • Cerebellum / abnormalities*
  • Cerebellum / diagnostic imaging
  • Down Syndrome / diagnostic imaging*
  • False Positive Reactions
  • Female
  • Fetal Diseases / diagnostic imaging*
  • Frontal Lobe / abnormalities*
  • Frontal Lobe / diagnostic imaging
  • Gestational Age
  • Humans
  • Karyotyping
  • Maternal Age
  • Odds Ratio
  • Predictive Value of Tests
  • Pregnancy
  • Pregnancy Trimester, Second
  • ROC Curve
  • Sensitivity and Specificity
  • Thalamus / diagnostic imaging
  • Ultrasonography, Prenatal*