The name is absent

Autism prodrome 29 of 89

than population norms at birth but there was accelerated growth such that by age 6-14
months with 53% of the sample revealing macrocephaly. Furthermore, in this small
case series enlarged head circumference was positively associated with measures of
autism symptom severity.

A number of subsequent reports broadly confirmed the finding of accelerated
head growth during the first year (though not the finding of abnormally small head
size at birth) with a subsequent decline in trajectory from the 2^nd year of life (Dawson
et al., 2007; Dementieva et al., 2005; Fukumoto et al., 2008; Hazlett et al., 2005). A
number of structural imaging studies have also found increased brain volume or
increases in specific brain structure in 2 to 4 year children with ASD (Aylward,
Minshew, Field, Sparks, & Singh, 2002; Courchesne et al., 2001; Hazlett et al., 2005;
Sparks et al., 2002). Two reports of head circumference in sibling studies have found
an association between enlarged head circumference or head circumference growth
rate and early emerging symptoms (Elder, Dawson, Toth, Fein, & Munson, 2008) or
initial ASD diagnosis at 24 months (Zwaigenbaum et al., 2008). However, in the only
study to examine whether head circumference growth differed between children with
and without a history of regression, no differences were found (Webb et al., 2007).

A note of caution is warranted since other studies have not replicated the
finding of increased trajectory of head circumference in the first year (Torrey,
Dhavale, Lawlor, & Yolken, 2004; van Daalen, Swinkels, Dietz, van Engeland, &
Buitelaar, 2007), and in some studies body length and weight also showed differences
from population norms. Another caution is that we do not know yet how many
children undergo this abnormal brain growth trajectory as most studies have analyzed
differences only in terms of groups, so suggestions that measurement of head

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