One of the (at least theoretically) most easily detectable features of fetal alcohol
syndrome (FAS) and fetal alcohol spectrum disorders (FASD) is a distinct pattern of
facial characteristics. However, in many children prenatally exposed to alcohol, these
characteristics are expressed only subtly, making it difficult to correctly identify
children with these disorders. To date, several studies have used conventional two-dimensional
images to develop computerized programs assisting in the identification of individuals
with FAS or FASD. However, many of the subtle features of prenatal alcohol exposure
cannot be visualized using two-dimensional images. Therefore, researchers at the Collaborative
Initiative on Fetal Alcohol Spectrum Disorders (CIFASD; http://www.cifasd.org) have
been using a special camera system that can generate three-dimensional images, which
allows them to explore the advantages of using such images to identify subtle facial
differences between individuals who were exposed to alcohol prenatally and individuals
who were not. This approach may help investigators and clinicians to better understand
the complications that may arise from prenatal alcohol exposure. For example, CIFASD
researchers can use facial measurements or shapes obtained from the three-dimensional
images to predict the presence of FAS, examine associations between facial shapes
and cognitive deficiencies, or better understand how the facial growth of a person
with FAS compares with facial growth in someone not prenatally exposed to alcohol.
Through an international consortium, CIFASD has been addressing these questions in
various age groups as well as different ethnic groups.
The Three-Dimensional Camera System and Image Analysis
The camera system used to obtain the three-dimensional images consists of two pods
attached at each end of a long arm that is mounted to a standard camera tripod (see
figure 1). Each pod contains three cameras and two flashes so that a total of six
photographs are generated. These six photographs, which eventually comprise the three-dimensional
image, are obtained in 1.5 milliseconds, similar to normal flash photography. The
attached laptop computer system uses special software to automatically stitch together
the six photographs (see figure 2), generating the final three-dimensional image in
less than 2 minutes (see figure 3). Although the camera system looks big and bulky,
it can easily be taken apart and packed into two cases. As a result, CIFASD researchers
have the ability to transport the camera anywhere in the world, take three-dimensional
images of dozens of children within a day, and electronically transfer these images
to a secure computer for analysis.
The three-dimensional images can be analyzed in several ways. One of the simpler analytic
strategies is to measure the length, width, or height of various portions of the face,
such as the length of the eye, width of the forehead, or height of the upper face
(figure 4). CIFASD investigators have used these measurements to evaluate whether
these parameters differ in people with and without prenatal alcohol exposure. The
analyses found that by using a subset of these measurements as predictor variables
in a statistical method called logistic regression, one can accurately classify children
in a given sample into two groups: those with FAS and those who were not exposed to
alcohol prenatally. For example, when studying children from Cape Town, South Africa,
CIFASD researchers identified a set of measurements that could correctly classify
94 percent of children with FAS and 91 percent of children without prenatal alcohol
exposure (Moore et al. 2007). Using the same statistical approach, but with a group
of children from Helsinki, Finland, the researchers also identified a set of facial
measurements that correctly classified 96 percent of children with FAS and 91 percent
of those without prenatal alcohol exposure. Interestingly, the sets of facial measurements
that best identified the respective groups differed between the South African and
Finnish samples. However, in both groups small eye width was one of the parameters
that helped to predict FAS (Moore et al. 2007). These results support previous observations
that small eye widths are a key feature distinguishing individuals with FAS and without
prenatal alcohol exposure.
CIFASD researchers now are seeking to understand why some unique facial features helped
predict group membership in the South African and Finnish samples. One possibility
is that these differences are caused by facial variation attributable to ethnicity.
Alternatively, the differences may be related to age differences between the two samples
because the South African children, on average, were much younger than the Finnish
participants, and previous studies already noted that the facial characteristics of
people with FAS change with age (Mutsvangwa et al. 2010; Streissguth et al. 1991).
Another way to analyze three-dimensional images is to place specific landmarks on
the images and then connect the landmarks with lines that generate shapes (see figure
5) (Mutsvangwa and Douglas 2007), a method that originally was proposed by Clarren
and colleagues (1987). Using an approach called morphometrics, one then can look at
differences between the shapes found in the faces of children prenatally exposed to
alcohol and those found in the faces of nonexposed children. To achieve this, the
shapes obtained from the faces of all subjects are aligned statistically so that they
then can be compared between the two groups (i.e., people with FAS and control individuals)
(Douglas and Mutsvangwa 2010). Similarly, one can compare the shapes between younger
and older individuals (Mutsvangwa et al. 2010). Using this approach, researchers can
examine what information specific shapes can provide about an individual’s face—such
as the fullness of the face, slower growth in certain facial areas, or asymmetries
between the two sides of the face. Thus, CIFASD researchers have found that differences
exist in the shape of particular facial regions between children with FAS and controls
(Klingenberg et al. 2010). In addition, certain differences in facial shapes appear
to be related to performance on tests that measure cognitive function (i.e., IQ) (Wetherill
et al. 2009). Findings such as these are important because they begin to allow researchers
to better understand how prenatal alcohol exposure affects development, both in the
face and in the brain.
Potential Applications of the Three-Dimensional Imaging System
The three-dimensional facial imaging system has several potential applications that
may aid researchers and clinicians in identifying individuals with FAS and delineating
the consequences of prenatal alcohol exposure. For example, the technology may allow
researchers to track how the facial features associated with prenatal alcohol exposure
change as an individual grows up. Studies currently are underway in a group of children
seen in South Africa in 2005, when most of them were 5 years old, and then again in
2009, when they were 9 years of age. Analyzing data from both time points, CIFASD
researchers found that during this time period, children with FAS exhibited faster
growth than non–alcohol-exposed children in particular parts of the face. As a result,
the facial features most characteristic of FAS (i.e., small eyes and small face) became
larger, making the facial features less distinct (Mutsvangwa et al. 2010; Wetherill
et al. 2010). This observation confirms previous reports by doctors and clinicians
who specialize in the effects of prenatal alcohol exposure that the facial features
of children with FAS become less obvious as the children age.
Another application currently being explored by members of CIFASD is the opportunity
to study changes in the faces of younger children. To this end, CIFASD is working
with a team of pediatricians at Tygerberg Hospital, a part of Stellenbosch University
Medical School, South Africa, to take three-dimensional images of babies at 1 month
of age and again at 12 months. The investigators hope to enroll about 1,200 babies
in the study, about 600 of whom will have been prenatally exposed to alcohol. Extensive
data is available on the children’s prenatal alcohol exposure, which will allow the
research team to study how the babies’ faces change during the first year depending
on the amount and timing of the prenatal alcohol exposure.
Finally, studies involving participants of differing ages, races, and ethnicities
will allow the CIFASD team to devise new ways to identify children with prenatal alcohol
exposure. Because it is essential for the children’s prognosis to initiate interventions
as early as possible, this approach using the three-dimensional camera and image analysis
can lead to earlier detection of and intervention for those at greatest risk.