Recent in vivo diffusion brain imaging studies of schizophrenic patients ha
ve revealed microstructural abnormalities, with low diffusion anisotropy pr
esent throughout much of cortical white matter. Brain anisotropy is produce
d when proton movement reflects physically restricted water movement, for e
xample, by myelin sheaths. Conditions that increase self-diffusion, such as
edema, may also alter the longitudinal and transverse relaxation time of p
rotons, and it is possible that such changes could explain the observed ani
sotropy diminution seen in schizophrenia. To test this possibility, we calc
ulated pixel-by-pixel transverse relaxation time (T2) and proton density (P
D) maps for gray matter and white matter across eight 5-mm-thick axial slic
es of fast spin echo MRI in 10 control men (age 30-57 years) and 10 men wit
h schizophrenia (age 32-64 years). Schizophrenics had significantly longer
mean white matter T2 (84.0 vs. 81.9 ms, P < 0.03) and gray matter T2 (95.1
vs. 92.2, P = 0.003); their mean white and gray matter PD values were not s
ignificantly different from those of controls. Correlations were not signif
icant between anisotropy and T2 in either grey or white matter but were sig
nificant between anisotropy and PD in white matter. T2 relaxation times are
longer in schizophrenics than in controls in both gray and white matter wh
ereas anisotropy reduction is restricted to white matter. Taken together, t
hese results suggest that the process producing prolonged T2 does not fully
account for the abnormally low anisotropy observed selectively in white ma
tter in this group of schizophrenic patients. (C) 1999 Elsevier Science Ire
land Ltd. All rights reserved.