Effects of fetal alcohol syndrome on facial shape Christian Peter Klingenberg Faculty of Life Sciences University of Manchester

Can we quantify these facial features? (from Wikipedia) Can we quantify these facial features? Can facial shape be used for diagnosis? Are there other effects on facial shape?

Mutsvangwa T, Douglas TS (2007) Morphometric analysis of facial landmark data to characterize the facial phenotype associated with fetal alcohol syndrome. J Anat 210:209–220.

Sample sizes (individuals with complete and usable data) Location FAS Controls African Americans 9 11 Cape Town 49 54 Finland 40 North American Caucasians 14 18

Landmarks used in the study This is a subset of an original landmark set designed for computing distances Moore, E. S., Ward, R. E., Wetherill, L. F., Rogers, J. L., Autti-Rämö, I., Fagerlund, Å., Jacobson, S. W., Robinson, L. K., Hoyme, H. E., Mattson, S. N., Foroud, T. and CIFASD (2007) Unique facial features distinguish fetal alcohol syndrome patients and control in diverse ethnic populations. Alcoholism Clinical and Experimental Research 31, 1707–1713.

Extracting shape information: Procrustes superposition Original landmark configurations 1. Change scale so that all configurations have the same size 2. Superposition of the centers of gravity on a single point 3. Rotation to minimize the dispersion of corresponding points

Shape change associated with the canonical variate 2 (Change by 5 units in positive direction: control to FAS)

Discriminant scores (all countries pooled) 106 / 137 correct 103 / 112 correct Discriminant scores (all countries pooled) Direct computation 104 / 137 correct 100 / 112 correct Cross-validation

Discriminant scores (Cape Town only) 50 / 54 correct 48 / 49 correct Discriminant scores (Cape Town only) Direct computation 45 / 54 correct 44 / 49 correct Cross-validation

Shape change associated with FAS in the Cape Town sample (Actual difference in average shapes: control to FAS)

Facial shape differentiates between FAS and control groups. Individuals can be assigned to the correct group with approximately 75% reliability or better. Prospect: different set of landmarks, improving the coverage of midface and upper lip.

Discriminant scores (Finland only) 46 / 54 correct 38 / 40 correct Discriminant scores (Finland only) Direct computation 37 / 54 correct 30 / 40 correct Cross-validation

Shape change associated with FAS in the Finnish sample (Actual difference in average shapes: control to FAS)

Correction for effects of size: allometry Single group Two groups

Allometry: regression of shape on size

Allometric regression Shape change for an increase of centroid size by 100mm

Canonical variate analysis of size-corrected shape data

Shape change associated with the canonical variate 2 of size-corrected shape data (Change by 5 units in positive direction: control to FAS)

Discriminant scores (from size-corrected data, all countries) Direct computation 120 / 137 correct 108 / 112 correct Cross-validation

53 / 54 correct 49 / 49 correct Discriminant scores (Cape Town only, after size correction by pooled within- group regression) Direct computation 51 / 54 correct 49 / 49 correct Cross-validation

Shape change associated with FAS in the Cape Town sample (after size correction by pooled within-group regression) (Actual difference in average shapes: control to FAS)

54 / 54 correct 40 / 40 correct Discriminant scores (Finland only, after size correction by pooled within- group regression) Direct computation 51 / 54 correct 40 / 40 correct Cross-validation

Shape change associated with FAS in the Finnish sample (after size correction by pooled within-group regression) (Actual difference in average shapes: control to FAS)

Size-correction by pooled within-group regression of shape on size greatly increases the performance of discriminant functions. Problem: this method of size correction uses information on group membership, and is therefore not applicable in the diagnostic context. Other methods of size correction do not improve the performance of discriminant functions by much.

Mean asymmetry of facial shape (Asymmetry is exaggerated 10-fold for better visibility.)

Discriminant scores for facial asymmetry (Cape Town only) 49 / 54 correct 40 / 49 correct Discriminant scores for facial asymmetry (Cape Town only) Direct computation 40 / 54 correct 35 / 49 correct Cross-validation

Difference of asymmetry associated with FAS in the Cape Town sample (Asymmetry is exaggerated 10-fold for better visibility.)

Discriminant scores for facial asymmetry (Finland only) 46 / 54 correct 36 / 40 correct Discriminant scores for facial asymmetry (Finland only) Direct computation 37 / 54 correct 25 / 40 correct Cross-validation

Difference of asymmetry associated with FAS in the Cape Town sample (Asymmetry is exaggerated 10-fold for better visibility.)

FAS also affects facial asymmetry. This finding is likely to raise questions and offer new ways of research on the developmental etiology of FAS.

Thanks to: CIFASD and clinical study sites Tatiana Foroud Leah Flury Wetherill Elizabeth Moore Richard Ward Jeff Rogers