Surface anatomy of the face in Down's syndrome: linear and angular measurements in the craniofacial regions.

Measurements (23 projective linear, 2 angular) taken in the 6 craniofacial regions of 127 patients with Down's syndrome showed that 63.1% (1,836 of 2,908) were within normal limits and 36.9% (1,072) were outside them. Abnormal measurements were subnormal in 90.8% (973) and supernormal in 9.2% (99). All statistical summaries were based on z scores (adjusting for age and sex differences) classified into a small number of ranges to yield a simplified frequency distribution for each measurement. The purpose of the study was to identify the measurements closest to normal and those indicating the most severe degrees of sub- or supernormality. Approximately a quarter of normal measurements were classified as optimal, and half the subnormal or supernormal measurements were classified as severe. Intercanthal width had the highest frequency of optimal measurements (93.7%, 119 of 127), head circumference the smallest (28.6%, 36 of 126). Knowledge of the frequency of extreme abnormalities in the craniofacial regions will help during visual examination of patients with Down's syndrome. This study found the highest percentage of severely subnormal measurements in the orbital region (57.8%, 74 of 128) and the smallest in the labio-oral region (32.7%, 16 of 49). The measurement with the highest proportion of severely subnormal to all subnormal values was the palpebral fissure length (68%, 51 of 75), and the nose width had the smallest proportion (14.3%, 1 of 7).