White matter fractional anisotropy and outcome in schizophrenia

Disparate white matter fractional anisotropy (FA) findings have been reported in patients with schizophrenia in recent years. This may in part reflect heterogeneity of subjects in the studies, including differences in outcome and severity of the illness. We examined whether there is a relationship between white matter FA and outcome in patients with schizophrenia.

Diffusion-tensor images were obtained in 41 normal subjects and 104 patients with schizophrenia, divided into good-outcome (n=51) and poor-outcome (Kraepelinian; n=53) subtypes based on their ability for self-care. White matter FA and its relationship to regional tissue volumes were evaluated across 40 individual Brodmann's areas using a semi-automated parcellation technique.

Overall white matter FA was lower in schizophrenia patients than normal subjects, with regional reductions in widespread temporoparietal and selected prefrontal white matter regions. In schizophrenia patients, lower regional white matter FA was associated with lower regional gray matter volumes. In comparison to normal subjects, overall white matter FA was reduced in patients with poor outcomes in both hemispheres, but to a lesser extent and only in the right hemisphere in good-outcome patients. Lower regional FA was associated with larger regional white matter volumes in good-outcome group.

Global FA reductions implicate white matter as tissue type in the pathophysiology of schizophrenia. In contrast to poor outcome, good outcome in schizophrenia patients may be associated with less extensive FA reductions, higher FA in regional frontal and cingulate white matter, and correlated increases in regional white matter volumes, particularly in the left hemisphere.