Microcephaly in a normal school population.

Heights, weights, and head circumferences were obtained on 1,006 students, ages 5 to 18 years, attending regular classes in four schools in a suburban Seattle school district. From the 1,006 students initially examined, 19 (1.9%) had a head circumference two or more standard deviations below the mean for age and sex. Intelligence quotients and academic achievement scores were obtained on these children and compared with normal controls. No significant difference was found between mean IQs of the study subjects and the controls (99.5 vs. 105), but mean academic achievement scores were significantly lower in the study subjects (49 vs. 70; P less than .001). In addition, although mean IQs were not significantly different between those subjects whose head circumference was proportional and those whose head circumference was relatively small, mean academic achievement scores were significantly higher (60 vs 39; P less than .02) in those subjects whose head size was proportional.