Objectives: 1) To construct an adult head measurement reference chart for typically developing adults that takes height into consideration, and that could be used for clinical purposes. 2) To compare the proportion of macrocephaly among a group of autistic adults and a group of typically developing adults.
Methods: 1) 100 male adults will be recruited among personnel at Rivières-des-Prairies Hospital and students at the University of Montreal in order to construct the reference scale. Height, weight and head size will be measured. 2) Two groups of 40 male subjects, autistic and non-autistic (aged 18-40; IQ between 80 and 130), will be recruited within the hospital’s database. Non-autistics who experienced past head trauma and who have a family history of psychological/neurological disorders, and autistics who have evident neurological/medical anomalies or other axis 1 disorders (except ADHD and dysphasia), are excluded from the study. Between-group differences will be tested using the scores obtained from the newly-made reference scale. Macrocephaly is defined as head circumference above the 97th percentile when controlling for height.
Results: 1) For the reference scale, so far, we have obtained measurements from 49 participants. Preliminary results show a positive relationship between head circumference and height (r=0.36). 2) So far, complete data have been obtained for 12 autistic and 20 typically developing participants matched on Wechsler full-scale IQ (F=0.378, p=.54). Preliminary results show a 16.7% prevalence of macrocephaly in the autistic group compared to no macrocephaly cases in the typically developing control group (according to Bushby’s 1992 chart, as a temporary reference).
Conclusions: Preliminary findings in a reference group indicate the necessity of taking height into account when measuring head circumference. Preliminary findings in the head circumference comparison study indicate that macrocephaly in autism persists into adulthood.