Temporal lobe, autism, and macrocephaly.
OBJECTIVE
Because of increased prevalence of macrocephaly in autism, head size must be controlled for in studies that examine volumetric findings of the temporal lobe in autistic subjects. We prospectively examined temporal lobe structures in individuals with autism who were normocephalic or macrocephalic (head circumference > 97th percentile) and in control subjects who were normocephalic or macrocephalic or who had a reading disorder (unselected for head size). The rationale for the reading disorder group was to have control subjects with potential temporal lobe anomalies, but who were not autistic.


METHODS
In individuals aged 7-31 years, autism was diagnosed on the basis of standardized interview and diagnostic criteria. Control subjects ranged in age from 7 to 22 years. All subjects were male. MR morphometrics of the major temporal lobe structures were based on ANALYZE segmentation routines, in which total brain volume and total intracranial volume (TICV) were calculated. Both group comparisons and developmental analyses were performed.


RESULTS
No distinct temporal lobe abnormalities of volume were observed once head size (TICV) was controlled for. In autistic and control subjects, robust growth patterns were observed in white and gray matter that differed little between the groups. Although subtle differences were observed in some structures (ie, less white matter volume in the region of the temporal stem and overall temporal lobe), none was statistically significant.


CONCLUSIONS
No major volumetric anomalies of the temporal lobe were found in cases of autism when IQ, TICV, and age were controlled. Temporal lobe abnormalities that may be associated with autism are likely to be more related to functional organization within the temporal lobe than to any gross volumetric difference.
Bigler
Erin D
ED
Department of Psychology and Neuroscience, Brigham Young University, Provo, UT, USA.
Tate
David F
DF
Neeley
E Shannon
ES
Wolfson
Lara J
LJ
Miller
Michael J
MJ
Rice
Sara A
SA
Cleavinger
Howard
H
Anderson
Carol
C
Coon
Hilary
H
Ozonoff
Sally
S
Johnson
Michael
M
Dinh
Elena
E
Lu
Jeff
J
Mc Mahon
William
W
Lainhart
Janet E
JE
D000293:Adolescent; D000328:Adult; D000375:Aging; D001321:Autistic Disorder / Q000175:diagnosis* / Q000523:psychology; D001921:Brain / Q000473:pathology; D016022:Case-Control Studies; D002648:Child; D000013:Congenital Abnormalities / Q000175:diagnosis; D006257:Head / Q000002:abnormalities* / Q000473:pathology*; D006801:Humans; D007360:Intelligence; D008297:Male; D013702:Temporal Lobe / Q000473:pathology*