Mean diffusivity: A biomarker for CSF-related disease and genetic liability effects in schizophrenia
Source: Psychiatry Research Neuroimaging
2009 Jan;171(1):20-32.
Author: Narr KL, Hageman N, Woods RP, Hamilton LS, Clark K, Phillips O, Shattuck DW, Asarnow RF, Toga AW, Nuechterlein KH PubMed ID: 19081707
Abstract:
Mean diffusivity (MD), the rotationally invariant magnitude of water diffusion that is greater in cerebrospinal fluid (CSF) and
smaller in organized brain tissue, has been suggested to reflect schizophrenia-associated cortical atrophy. Regional changes,
associations with CSF, and the effects of genetic predisposition towards schizophrenia, however, remain uncertain. Six-direction
diffusion tensor imaging DTI and high-resolution structural images were obtained from 26 schizophrenia patients, 36 unaffected
first-degree patient relatives, 20 control subjects and 32 control relatives (N=114). Registration procedures aligned diffusion tensor
imaging (DTI) data across imaging modalities. MD was averaged within lobar regions and the cingulate and superior temporal gyri.
CSF volume and MD were highly correlated. Significant bilateral temporal, and superior temporal MD increases were observed in
schizophrenia compared with unrelated control probands. First-degree relatives of schizophrenia probands showed larger MD
measures compared with controls within bilateral superior temporal regions with CSF volume correction. Superior temporal lobe
brain tissue deficits and proximal CSF enlargements are widely documented in schizophrenia. Larger MD indices in patients and
their relatives may thus reflect similar pathophysiological mechanisms. However, persistence of regional MD effects after
controlling for CSF volume, suggests that MD is a sensitive biological marker of disease and genetic liability, characterizing at least
partially distinct aspects of brain structural integrity.