Fourier analysis of the cranium in trisomy 21.

A comparative study of individuals exhibiting the trisomy 21 syndrome (Down's) and a normal group has shown statistically significant differences in cranial shape (norma lateralis). These differences illustrate the departure from normal growth seen in individuals displaying the trisomy 21 syndrome. Fourier analysis is a preferred method since it is more efficient than conventional techniques in the analysis of complex shapes. Fourier analysis is also attractive because the series terms are orthogonal, hence independent; further, the Fourier approach allows for the control of size differences. A three-way analysis of variance was used to test for significant differences between mean Fourier coefficients. The results showed significant difference between individuals with trisomy 21 and controls. Age differences were also significant, only sex differences tended to be non-significant. Finally, the trisomy 21 sample is twice as variable as the controls.