Anterior commissural white matter fiber abnormalities in first-episode psychosis: a tractography study

Abstract

Background: The Anterior Commissure (AC) is an important interhemispheric pathway that connects contralateral temporal lobes and orbitofrontal areas. The role of the AC is not yet well understood, although abnormalities in this white matter tract have been reported in patients diagnosed with chronic schizophrenia. However, it is not known whether changes in the AC are present at earlier stages of the disease.

Methods: Diffusion Magnetic Resonance Images (dMRI) were acquired from 17 First Episode Schizophrenia Patients (FESZ) and 20 healthy controls. The AC was reconstructed using a streamline tractography approach. DMRI measures, including Fractional Anisotropy (FA), Trace, Axial Diffusivity (AD) and Radial Diffusivity (RD) were computed in order to assess microstructural changes in the AC.

Results: FA was reduced, while trace and RD showed increases in FESZ. AD did not show differences between groups.

Conclusion: The observed changes in these dMRI measures, namely reductions in FA and increases in trace and RD, without changes in AD, likely point to myelin abnormalities of this white matter tract, and provide evidence of white matter pathology extant in the early phases of schizophrenia.

Keywords: Anterior commissure (AC); Diffusion Tensor Magnetic Resonance Imaging (dMRI); First-episode schizophrenia; Fractional anisotropy (FA); Radial diffusivity (RD); Tractography.