Several characteristic craniofacial abnormalities are often visible in individuals with FAS. The presence of FAS facial features indicates brain damage, though brain damage may also exist in their absence. FAS facial features (and most other visible, but non-diagnostic, deformities) are believed to be caused mainly during the 10th and 20th week of gestation.
Refinements in diagnostic criteria since 1975 have yielded three distinctive and diagnostically significant facial features known to result from prenatal alcohol exposure and distinguishes FAS from other disorders with partially overlapping characteristics. The three FAS facial features are:
A smooth philtrum — The divot or groove between the nose and upper lip flattens with increased prenatal alcohol exposure.
Thin vermilion — The upper lip thins with increased prenatal alcohol exposure.
Small palpebral fissures — Eye width decreases with increased prenatal alcohol exposure.
Measurement of FAS facial features uses criteria developed by the University of Washington. The lip and philtrum are measured by a trained physician with the Lip-Philtrum Guide, a 5-point Likert Scale with representative photographs of lip and philtrum combinations ranging from normal (ranked 1) to severe (ranked 5). Palpebral fissure length (PFL) is measured in millimeters with either calipers or a clear ruler and then compared to a PFL growth chart, also developed by the University of Washington.
Ranking FAS facial features is complicated because the three separate facial features can be affected independently by prenatal alcohol. A summary of the criteria follows:
Severe — All three facial features ranked independently as severe (lip ranked at 4 or 5, philtrum ranked at 4 or 5, and PFL two or more standard deviations below average).
Moderate — Two facial features ranked as severe and one feature ranked as moderate (lip or philtrum ranked at 3, or PFL between one and two standard deviations below average).
Mild — A mild ranking of FAS facial features covers a broad range of facial feature combinations:
Two facial features ranked severe and one ranked within normal limits,
One facial feature ranked severe and two ranked moderate, or
One facial feature ranked severe, one ranked moderate and one ranked within normal limits.
None — All three facial features ranked within normal limits.
These distinctive facial features in a patient do strongly correlate to brain damage. Sterling Clarren of the University of Washington's Fetal Alcohol and Drug Unit told a conference in 2002:
“I have never seen anybody with this whole face who doesn't have some brain damage. In fact in studies, as the face is more FAS-like, the brain is more likely to be abnormal. The only face that you would want to counsel people or predict the future about is the full FAS face. But the risk of brain damage increases as the eyes get smaller, as the philtrum gets flatter, and the lip gets thinner. The risk goes up but not the diagnosis.“
“At one-month gestation, the top end of your body is a brain, and at the very front end of that early brain, there is tissue that has been brain tissue. It stops being brain and gets ready to be your face ... Your eyeball is also brain tissue. It's an extension of the second part of the brain. It started as brain and "popped out." So if you are going to look at parts of the brain from alcohol damage, or any kind of damage during pregnancy, eye malformations and midline facial malformations are going to be very actively related to the brain across syndromes ... and they certainly are with FAS.“