To verify the hypothesis that volume of regional gray matter accounts substantially for variability in intelligence quotient (IQ) score among children with sickle cell disease, who have no magnetic resonance visible infarcts.
We studied 31 children with sickle cell disease, homozygous for hemoglobin S, with no history of stroke, no magnetic resonance signal-intensity abnormality, and transcranial Doppler velocities <170 cm/sec, with a T1-weighted magnetic resonance sequence and the Kaufman Brief Intelligence Test. On the basis of Kaufman Brief Intelligence Test, we classified these children into 2 groups: high and low IQ based on a median split. We then used an automated and novel Bayesian voxel-based morphometry technique, called Graphical-Model-Based Multivariate Analysis (GAMMA), to assess the probabilistic association between IQ score and regional gray matter volume.
GAMMA found 1 region linking low IQ with smaller cortical gray matter volume. In comparison with the children in the high-IQ group, children in the low-IQ group had smaller regional gray matter volume in both frontal lobes, both temporal lobes, and both parietal lobes.
In children with sickle cell disease, we found a linear association between IQ and regional gray matter volume. This finding suggests that some variance in intellectual ability in children with sickle cell disease is accounted for by regional variability of gray matter volume, which is independent of neuroradiological evidence of infarct.
From the *Department of Radiology, University of Pennsylvania, Philadelphia, PA; †Department of Psychology at The Children's Hospital of Philadelphia, Philadelphia, PA.
Received March 13, 2009; accepted September 11, 2009.
Rong Chen, Mikolaj A. Pawlak, and Edward H. Herskovits were supported by National Institutes of Health grant R01 AG13743, which is funded by the National Institute of Aging, the National Institute of Mental Health, and the National Cancer Institute. Thomas B. Flynn, Jaroslaw Krejza, and Elias R. Melhem were supported by National Institutes of Health grant 5-R01-NS-046717.
Address for reprints: Rong Chen, PhD, Department of Radiology, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104; e-mail: firstname.lastname@example.org.